Our analytical services department run samples for scores of important customers every year. Whilst we obviously cannot share customer confidential information, some customers have kindly given us permission to share some of the more interesting results we observed using their compounds.

Subcutaneous injection is a popular route of administration for non-oral drugs such as biotherapeutics. Historically, there has been no in vitro test to evaluate performance of subcutaneous formulations. Invented by an academic pioneer in the field, the Pion Scissor addresses this gap.

Log P is one of the most important and useful properties that drug researchers can measure. In this fascinating webinar, we explore the history of Log P, and describe its use in today’s pharmaceutical industry

Hydrogen bonding plays a key role in in vivo drug behavior: For example how APIs can interact with and permeate membranes. In this webinar, a leader in the field, Giulia Caron of the University of Turin, joins us to describe methods for observing hydrogen bonding effects.

This is our first pKa webinar. In it, we describe the origins of the measurement, the origins of the science we use for our measurement platform and show you some of the extremely accurate data generated by the Pion SiriusT3

We have previously shown you how we measure pKa. This follow on webinar will describe why pKa is considered such a critical measurement in drug discovery and development environments.

Pion have long been the leader in pKa measurement. We have several techniques perfected, but the most popular of these with both our in-house chemists and our customers are those methods based on UV spectrophotometry. These methods are fast, compound sparing, and extremely accurate. This webinar explains the scientific principles behind UV metric pKa measurement.

pKa is a core competence of Pion, and we have many methods for measuring it. This webinar explains the concepts of pKa measurement, the experimental means of measuring it, and the key role that this property plays in the behavior of drugs.

A known issue in drug formulation is the tendency of certain drugs, particularly weak bases, to dissolve initially in the gastric environment and then re-precipitate in the intestine. This webinar describes several in vitro strategies for stimulating, measuring and mitigating this effect.

One of the key challenges for formulators is making in vitro experiments relevant to in vivo outcomes. Among the strategies for obtaining this data are the use of biphasic dissolution experiments in order to get measures of aqueous dissolution and permeability in parallel, and also the use of biorelevant media such as FaSSGF, FaSSIF and FeSSIF to more accurately simulate the dissolution environment within the human body. This webinar explores real-world use of some of these techniques.

This webinar describes some methods for investigating compounds’ tendency to supersaturate, and the use of various excipients such as crystallization inhibitors to exploit this tendency and therefore enhance and/or prolong solubility

There are several effective ways to measure solubility, with most leading to an equilibrium solubility endpoint. Pion’s patented CheqSol™ method is a sophisticated assay allowing the observation of all intermediate solubility steps, such as supersaturated, metastable states.

This is one of our most popular webinars. Joined by our very good customer Cyprotex, we explore why understanding physchem properties is vital when it comes to understanding the ADMET behaviors of APIs

There are multiple traditional, miniaturized and innovative techniques for measuring solubility. Depending upon throughput, purpose, and richness of experimental data required, any of these techniques may be appropriate. This webinar explores some different options in the hope of guiding you towards the best method for achieving your goals.

This webinar describes the Pion inForm and the various Biorelevant assays which it can run, such as Biorelevant dissolution, controlled supersaturation and GI lipolysis.

This podcast was recorded as a result of an especially well received presentation given by then-CSO John Comer. A great many small molecule drugs are weakly basic, leading to known pluses such as supersaturation potential and known issues such as intestinal precipitation. This podcast explores some of these effects using real APIs.

A second PowerPoint presentation containing several video clips to show modern techniques used to measure solubility, dissolution, pKa and log P/D using the SiriusT3.
These videos are produced in collaboration with the Royal Society of Chemistry.

A PowerPoint presentation containing several video clips to show modern techniques used to measure solubility, dissolution, pKa and log P/D.
These videos are produced in collaboration with the Royal Society of Chemistry.

This video shows the graceful mechanical functioning of our SiriusT3 during a CheqSol™ solubility experiment. It also gives some glimpses into our software and the results obtained from the experiment.

Purpose
For generic formulation development, traditional (USP) dissolution tests provide primary input parameters for predicting in vivo performance of different drug formulations before conducting bioequivalence studies. Although USP dissolution tests are relatively simple to conduct for testing formulations, the in vivo predictive power of these tests is questionable1. Namely, when a poorly water-soluble API is formulated to enhance its dissolution, additives, such as surfactants, polymers and cyclodextrins have an effect not only on dissolution profile, but also on flux through the membrane.

Purpose
The challenge of developing poorly soluble drugs continues to grow as more and more new chemical entities (NCEs) are poorly soluble. Formulation strategies often rely on maintaining a supersaturated state for poorly soluble drugs. A large portion of modern patients are medicated to reduce stomach acidity, and Drug–Drug Interactions (DDI) with Acid Reducing Agents (ARAs) an dramatically increase pharmacokinetic variability and decrease bioavailability—especially for weak bases. This study valuated pH-shift flux measurements as in vivo predictive tool for DDI assessment.

When a poorly water-soluble active pharmaceutical ingredient (API) is formulated to enhance its dissolution, additives, such as surfactants, polymers and cyclodextrins have an effect not only on dissolution profile, but also on flux through the membrane. In order to fully understand these effects on flux, the driving force of membrane transport cannot be simplified to the total concentration gradient.

Purpose
A novel in vitro method for predicting how the characteristics of the subcutaneous tissue may influence the post-injection stability and diffusional properties of subcutaneously administered biopharmaceuticals has been developed. Scissor subcutaneous injection site simulator mimics the human body conditions and allows to understand how a formulation influences the behaviour of a biotherapeutic in the subcutaneous (SC) injection site. This allows to expedite the identification of lead formulations with optimal absorption properties following injection and facilitating rational formulation design.

Purpose
The subcutaneous(SC) route of administration has gained much interest in recent years, showing higher levels of patient compliance than current IV methods and giving a cost-effective alternative for health organizations. For this reason, a better understanding in vivo behavior of these types of formulations is essential for more insightful development and application of these drugs in the future.

Purpose
The isoelectric point (pI) is the pH at which biological amphoteric molecules such as peptides and proteins carry no net electrical charge. Biopharmaceutical drug formulations that are intended for subcutaneous injection are often prepared at about pH 4 to enhance shelf life but when they are injected into the body the pH swiftly moves to 7.4. If the isoelectric point is between these pH values, there is increased risk of precipitation and aggregation after injection, which could diminish bioavailability. Isoelectric point values can be calculated precisely for molecules with only two ionizable groups, but are harder to estimate as the number of acidic and basic groups increases. Isoelectric point values are traditionally measured by electrophoresis, but here we present the measurement by potentiometric titration. This method has the advantage of high precision.

Purpose
Poorly soluble weak bases are susceptible to precipitation when travelling through the gastro‐intestinal tract following an increase of pH. The outcome for oral absorption may depend on the precipitation behaviour of the drugs. In this study we evaluate several methods for studying supersaturation and precipitation rates.

Poorly soluble weak bases may be susceptible to precipitation when travelling through the gastro‐intestinal tract following an increase of pH. Likewise, acidic compounds when dosed as salts may show initial rapid dissolution followed by precipitation at gastric pH values. The outcome for oral absorption may depend on the precipitation behaviour of the drugs. In this study we evaluate several methods for studying supersaturation and precipitation rates.

Purpose
The CheqSol solubility technique was used to measure kinetic and intrinsic solubility and identify compounds that cannot form supersaturated solutions, i.e., they immediately precipitate to the maximum extent allowed as soon as their solubility limit is exceeded. Surface tension measurements showed that most of these compounds were surface active substances with low polar surface area and a localized region of charge when they are ionized. These properties lead to ordered structures in solution which are thermodynamically stable over a wide range of conditions. The purpose of this work was to establish a link between supersaturation and surface activity.

Purpose
Phospholipidosis (PLD) is a lipid storage disorder characterised by the accumulation of phospholipids within cells, and has been found to be induced by several drugs. Whilst PLD is seen in humans with inherited metabolic disorders such as Niemann-Pick and Gauchers disease. It is also of concern as an adverse side effect of cationic amphiphilic drugs (CADs). Herein we introduce a novel high-throughput physicochemical screen for predicting the PLD-inducing potential of drugs.

The goal of this study was to demonstrate that the shape of UV-Vis extinction spectra caused by light scattering could provide information about the size of nano and microparticles that caused such scattering. This scatter-based particle size estimation was applied to characterize in situ the effective particle size of amorphous colloidal structures that kinetically form in solutions during supersaturation/precipitation transition.

Purpose
Directly observing dynamic processes such as crystallization and dissolution using particle size analysis can be difficult using traditional particle size analysis methods such as laser diffraction due to changes in the refractive index of the crystallization medium, pH and temperature. The studies described in this poster show that these processes can be readily followed using the model‐independent time-domain measurement of Laser Obscuration Time (LOT) and dynamic image analysis.

In this study the dissolution and precipitation behaviour of a co-crystal of the herbicide tebuconazole with squaric acid has been evaluated using the inForm.

The purpose of this work was to combine the Alicona® infinite focus microscope (IFM) with the new surface dissolution imaging system (SDi2) to detect similariDes or potenDal differences in the iniDal gel formaDon of HPMC CR and DC2 (K100M grades) pure polymer compacts

Currently, the acid resistance of the applied coat is determined by dissolution in a compendial dissolution apparatus with 0.1M Hydrochloric acid. Typically such methods require a prolonged running time (e.g. 2 hours) to understand the effect of prolonged exposure to acid and to establish a suitable solution concentration that can be measured. Also, it is not possible to determine were the tablet defects are (i.e. the embossed region).

Purpose
To derive the hydrogen bond acidity and hydrogen bond basicity of solute drug molecules from measurements of log P in octanol-water, chloroform-water, toluene-water and dodecane-water.

Purpose
The objective of this study was to use a Design of Experiments (DOE) approach to investigate how the potentiometric determination of the log P of sparingly soluble drugs is influenced by the amount and type of cosolvent.

Purpose
To demonstrate acid‐base titrations of proteins in small volumes.

Purpose
The solubility of insoluble compounds can be increased using solubility enhancing excipients. The behavior of different drug compounds in the presence of these solubility enhancing excipients can be measured using potentiometric pKa and solubility methods. This technique can be used to assess the relative effects on supersaturation and intrinsic solubility to give a better understanding of how the excipients enhance the solubility of the compounds.

Purpose
Organic molecules used as building blocks in drug discovery may have more than one tautomeric form. An example is 4-amino-2,6-dimethylphenylsulfonyl nitromethane (4-ADN) , an acidic molecule that exhibits aci-nitro tautomerism. In this work we used potentiometric titration to measure the pKa of this molecule, with the goal of forming tautomers and assessing their relative concentrations after exposure to acidic and basic conditions. A tendency to tautomerise might be considered a drawback in a molecular building block.

Purpose
The aim of this study was to evaluate the physicochemical properties of a series of isoniazid and benzimidazole Potentiometric Shake-Flask 3 Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Isoniazid derivatives. The aim of this study was to evaluate the physicochemical properties of a series of isoniazid and benzimidazole derivatives. Some of these derivatives have been shown to have promising anti-tubercular activity by comparison with isoniazid, and retain their activity against a panel of isoniazid-resistant bacteria strains. Their feasibility as drug-like candidates could be evaluated from information about their potency, together with Compound Structure M / g mol-1 pKa (I=0) Potentiometric log Po/w Shake-Flasklog Po/w Isoniazid A 137.14 pK1= 3.53 ± 0.04 pK2=11.14 ± 0.07 logPn= -0.65 ± 0.03 -0.85 ± 0.01 (N=4) NOHNNH2 feasibility as drug-like candidates could be evaluated from
information about their potency, together with knowledge of their lipophilicity logPo/w), which models their ability to penetrate biological membranes and their acid dissociation constant (pKa), which affects the charge and therefore the passive transport across the membrane and the activity in the living organism.

In this work, we sought a rapid way to determine pKa in 2-propanol using an aqueous pKa measurement procedure, and calibrating it with published values. The presence of water at low levels can change the solubility of organic compounds in organic solvents, and it is expected that water will also have a significant effect on speciation; however until recently, the change in pKa caused by small amounts of water in organic solvents had not been measured.

Purpose
To provide a simple chart to allow users to classify supersaturation and precipitation to provide better understanding during drug formulation.

Purpose
Pharmaceutical drug development pipelines continue to produce drugs with the challenge of poor aqueous solubility. Enabling formulation technologies, e.g., amorphous solid dispersions, are used to overcome such limitations via the creation of supersaturated states.

Purpose
To study the effect of the common excipients on the nucleation rate of the supersaturated API in simulated gastrointestinal media(SGIM).

Supersaturation, phase separation and measurement of precipitation rates.

Purpose
The purpose of this study is to learn about the supersaturated state of basic drugs and their precipitation behaviour. This was performed by addition of different types of excipients in the experimental set-up and studying the change in supersaturation time.

This poster describes how to create supersaturated solutions by the solvent quench method. Experiments were run on Pion inForm, a new instrument for studies to support drug formulation. Data quality is greatly enhanced by the automation.

Purpose
This poster describes recent work within the European funded OrBiTo project on the dissolution behaviour of BCS Class II poorly soluble) compounds using disk and powder methods and the impact of different media on the dissolution performance.

Purpose
This poster describes recent work within the European funded OrBiTo project on the dissolution behaviour of BCS Class II (poorly soluble) compounds using disk and powder methods and the impact of different media on the dissolution performance.

Purpose
To evaluate three dissolution methodologies used for characterizing the dissolution properties of two pharmaceutical salts of a weak base.

This project (INVITOX), currently at the start of the funding, aims to develop in vitro tests for drug toxicology studies. New tests,
mimicking more closely animal physiology, will limit the use of animals during formulation development.

Purpose
In a biphasic system, a drug molecule may partition from an aqueous phase to an immiscible organic phase in a process that is thought to be similar to passive diffusion of drugs across biological membranes. A Design of Experiments (DoE) model was used to explore the effects of pH, organic solvent type, excipients and biorelevant media on the partitioning rate.

Purpose
To determine the release mechanism of promethazine (PMZ) with either polyvinyl pyrrolidone-40 (PVP K40), Eudragit RS or Eudragit RL using the SDI (Surface Dissolution Imaging).

Purpose
Measuring the dissolution performance of nanoparticle suspensions presents some practical challenges as (i) the rate of dissolution is often very fast, reaching maximum concentration within seconds and, (ii) depending on the concentration of the suspension, turbidity may be encountered. For ex-situ analytical techniques, such as HPLC, a fast sample collection rate and reliable phase separation is required in order to measure the kinetics of the dissolution process, which is often not achievable. Therefore an in-situ technique is preferable. UV absorbance spectroscopy is commonly used for this purpose, however there are known spectral artefacts caused by particle absorbance and light scattering that can lead to inaccuracies in the results.

Purpose
Finding appropriate in-vitro modeling to predict in-vivo performance of oral dosage forms has always been challenging for pharmaceutical industries. In recent years there has been a push to improve biorelevance of in-vitro testing in an attempt to model complex in-vivo processes such as supersaturation and precipitation.

Purpose
The purpose of this study was to utilize proprietary dissolution technologies (SDi2) to investigate the effect of formulation differences on drug release for immediate (IR) and extended (ER) release Metformin tablets.

This poster describes experiments that model the dissolution of drugs under conditions of steadily increasing pH in the presence of t simulated intestinal fluid, a Biorelevant Medium (BM).

Understanding dissolution is an essential requirement during the pre-formulation stages of drug development, and the inclusion of UV imaging on the SDI provides a new perspective on the dissolution behaviour of drug substances for lead drug selection and formulation optimisation. The visualization of the dissolution phenomena provides a unique insight into the dissolution process of formulations as they happen, and the measurement of solution concentration directly at the solid/solution interface allows for the ranking of dissolution right from experimental onset. The SDI provides an understanding of early occurrences of the dissolution process otherwise missed when using traditional dissolution testing methods.

Application of the Surface Dissolution Imaging System (SDI) in Pharmaceuticals.

Use of SDI to assess dissolution characteristics of OTC pharmaceuticals with controlled release rate formulations.

Purpose
A “biphasic dissolution model” has recently been developed to mimic the absorption of drugs under changing (gastrointestinal) pH conditions. This has been further developed to include simulated intestinal fluids (SIF) to better understand their effect on the uptake of orally dosed pharmaceutical drugs.

Purpose
The bioavailability of poorly soluble drugs may be enhanced by incorporating them in a solid dispersion. Here, the drug is typically dispersed, either in discrete crystalline regions or molecularly, within an hydrophilic matrix. This has the effect of enhancing the dissolution rate of the drug, and subsequently forming a supersaturated system. A low volume dissolution assay was used to characterize the dissolution of small sample quantities. This method can be developed further as an automated screening assay for solid dispersions.

Purpose
To better understand the dissolution properties and precipitation behaviour of pharmaceutical cocrystals of poorly soluble drugs for the potential for oral administration based on a small scale dissolution assay.

Purpose
To develop a method for studying the ability of polymers to prevent drug precipitation in dissolution experiments under
changing (gastrointestinal) pH conditions and with a lipid phase to mimic absorption.

Purpose
To develop a stylized and easily generated profile of a drug’s dissolution in aqueous solutions, and its passage into a lipid phase to mimic absorption.

Purpose
At the 2008 AAPS Annual Meeting, we described the GI Dissolution Assay for assessing dissolution, supersaturation and precipitation of a pharmaceutical substance during passage through the gastrointestinal (GI) tract. In the current study, this assay method was used to investigate the dissolution of drugs in the presence of additives and simulated GI fluids.

Purpose
To better understand the dissolution properties and precipitation behaviour of carbamazepine cocrystals for the potential for oral administration based on a small scale dissolution assay.

A biphasic dissolution assay has been developed to measure the partition rate of API’s from an aqueous compartment into an immiscible organic phase in order to mimic the absorption of a compound through biological membranes. To understand how the amorphous solubility may affect absorption, the partition rate of felodipine was measured at concentrations above and below the amorphous solubility.

Purpose
The aim of the study was to measure the dissolution characteristics of various active pharmaceutical ingredients used in inhalation products using novel low volume assays. Samples were compared in a standard phosphate buffer and in several
simulated lung fluid (SLF) media.

Purpose
To assess the dissolution performance of felodipine:HPMCAS solid dispersions prepared using different spray drying conditions and to characterize the particle properties of each solid dispersion using laser obscuration time (LOT) and digital image analysis.

Automated Measurements of Precipitation, Supersaturation and Biphasic Dissolution.

Automated Measurements of Lipolysis, Supersaturation & Biphasic Dissolution

Purpose
A biphasic dissolution assay has been developed to mimic dissolution and absorption within the human gastrointestinal tract (GIT). The pH and composition of the aqueous phase can be adjusted to simulate GI conditions. The passage of drug into the lipid phase simulates the absorption into the gut wall. Biphasic dissolution experiments are quite complicated and involve many steps, and can be difficult to perform using conventional dissolution apparatus. The protocols described here take advantage of robotics and automation to ensure well‐designed, reproducible and successful experiments.

A biphasic dissolution assay has been developed to mimic dissolution and absorption within the human gastrointestinal tract(GIT). The pH and composition of the aqueous phase can be adjusted to simulate GI conditions. The passage of drug into the lipid phase simulates the absorption into the gut wall. Biphasic dissolution experiments involve many steps, and can be difficult to perform using conventional dissolution apparatus. The protocols described here take advantage of robotics and automation to ensure well-designed, reproducible and successful experiments.

This application note discusses two biphasic studies of felodipine. In the first, partition rates were measured at concentrations above and below its amorphous solubility to understand the impact of different dose levels on absorption. In the second,
solid dispersions of API of two different particle sizes were created in order to investigate dissolution-limited aspects of drug absorption. Experiments were performed using inForm, an instrument for biorelevant solubility and dissolution testing.

Purpose
To gain insight into the behaviour of structurally similar compounds in solution before, during and after precipitation.

Purpose
To verify that solubility of ionizable drugs measured in aqueous solution is correctly predicted from solubility measured in water‐methanol mixtures.

Purpose
The aim of this poster was to study the impact of several simulated lung fluid (SLF) media on the physicochemical properties of a selected group of inhaled drugs. Physicochemical properties such as pKa, log P, solubility and dissolution rates were measured at different conditions using protic and aprotic salts in phospholipid and surfactant systems to observe the impact of the media on the physicochemical properties of the drug. Sample properties were also compared with a standard phosphate buffer medium system.

Purpose
Triclosan is an antibacterial and antifungal agent found in numerous consumer products, including soaps and detergents. We investigated its pKa, log P and solubility, and its dissolution rates in biphasic systems to support research aimed at understanding its potential effects on organisms and environmental health.

Purpose
The aim of this study was to evaluate the supersaturation and precipitation behaviour of poorly soluble ionizable compounds in the presence of cellulose polymers (Klucel® EF and Pharmacoat® 603).

Purpose
Lipid based formulations are known to enhance the solubility of drug compounds [1]. The purpose of this study was to determine the intrinsic solubility enhancement of several drug compounds in the presence of a lipid based formulation at 37°C. The ratio of the components in the formulation were varied to investigate the effect of composition on the solubility of the compound.

Purpose
Prior to candidate selection, it is useful to assess the likelihood of weakly basic compounds to form insoluble HCl salts. Such salts could hinder oral absorption leading to costly formulation and development challenges. In this poster we describe a technique for measuring pHmax and determining the HCl salt solubility without the need to obtain crystals of the salts.

Purpose
To study the behavior of different Plasdone polymers and their ability to enhance the solubility of drugs in small volume assays. The small quantities of sample used enable the screening of drug solubility at various drug:Plasdone w/w ratios.

The purpose of this work was to validate the potentiometric determination of aqueous intrinsic solubility by extrapolation from measurements made in methanol-water mixtures.

Purpose
To study in real-time the crystallization tendency of drug compounds from super-saturated solutions using novel pH-metric
solubility methods and investigate the ability of Plasdone™ Povidone and Copovidone to inhibit crystallization.

Purpose
To investigate the intrinsic solubility of cocrystal coformers in the presence of the cocrystal API, using a pH-metric technique.

This study shows the feasibility of utilizing pH-metric titration for evaluating the supersaturation behavior of ionizable pharmaceutical compounds in real time as well as measuring the amorphous solubility of type II compounds.

Ionizable pharmaceutical compounds, especially weakly basic drugs, have pH dependent solubility and therefore are susceptible to supersaturation and precipitation when encountering pH changes in the gastrointestinal (GI) tract. Our previous study shows that two types of supersaturation behavior can be observed: type I compounds have short durations of supersaturation while type II compounds are able to maintain supersaturation for prolonged periods of time. The goal of this study is 1) to study the supersaturation behavior of a type I compound, dipyridamole, in the presence of polymers by Bjerrum plot, 2) to evaluate the effectiveness of polymers in maintaining supersaturation.

Experimental Methods for Investigating Experimental Methods for Investigating Drug Supersaturation Behavior: Promoting a Compound’s BCS Class

Purpose
Using potentiometric techniques, the kinetic and intrinsic solubility of several compounds were measured at 25 and 37°C to better evaluate this property at in vivo temperature. Twelve compounds were selected for differences in their supersaturation behavior. Diclofenac, sulfamerazine, metoclopramide, warfarin, dipyridamole, propranolol and pindolol all have slow recipitation kinetics which enable them to form supersaturated solutions (kinetic/intrinsic solubility > 1); compounds of this class are known as “Chasers” [1]. Chlorpromazine, imipramine, amitriptyline, diphenhydramine and dicyclomine all have fast precipitation kinetics that precludes the formation of supersaturated solutions (kinetic/intrinsic solubility = 1); compounds of this class are known as “Non-chasers” [1].

Purpose
During drug development, chemists need to choose salts with optimum properties for bioavailability and formulation. An important property of salts is their solubility. Values are typically measured after first creating the salt in crystalline form. We sought to develop a method for measuring salt solubility without the need to prepare crystals of the salts.

Purpose
Indomethacin has been described as “practically insoluble in water” [1]; solubilities between 2-7 µg/mL have been reported[2,3]. However a higher value of 410 µg/mL has also been proposed [4]. Uncertainty undermines computational efforts to predict solubility [5]. Which value is correct?

Purpose
Titrimetric methods for measuring pKa, logP and intrinsic solubility (S0) in drug development are powerful and accurate. However it has become increasingly difficult to apply them as the weight of sample available for analysis has decreased. To overcome these problems we developed an instrument (SiriusT3) with miniaturized sensors that performs automatic titration in 1 mL of solution. This enables titrimetric measurements using sub-mg sample weights, or samples pipetted from DMSO stock solutions. This poster validates the new instrument by measuring pKa, logP and solubility of 20 drug molecules, and comparing results with previously validated measured results. This will be the first published study carried out under routine laboratory conditions.

Purpose
To investigate the kinetic and intrinsic solubility of drugs and the amount of supersaturation in the presence of simulated gastrointestinal fluids and other formulation excipients.

Purpose:
In this study, we investigated the physicochemical characteristics of selected ß-blockers by measuring the pKa and intrinsic solubility of the compounds. The results were compared with calculated values and reported data found in the literature.

The SDi2 surface dissolution imaging system provides unique insights into physical phenomena that occur at the interface of a drug product and dissolution medium. These phenomena are by necessity overlooked using compendial dissolution techniques, because concentration measurements are usually taken downstream of the dissolution process, yet they are key to understanding the full picture of how a formulation will perform in vivo. The SDi2 is used to observe and measure such effects of erosion, swelling, disintegration and drug release from API compacts or formulated whole dosages in a single experiment, enabling rapid, informed decisions to be made during dosage form selection/optimization.

Here we present a validation study whereby IDR measurements using the SDi2 are compared with published values from using the USP rotating disk method. The SDi2 is a unique small-scale flow-through instrument for biorelevant IDR measurement of compacts, employing real-time UV/Vis imaging to create a video of the dissolution process directly at the solid-dissolution medium interface.

Purpose:
To study the solubility and supersaturation behavior of different basic compounds in the presence of Plasdone polymer.

This work aimed to introduce an in vitro method for qualitatively estimating food effect in early stages of pre-formulation and formulation based on the differences in the flux through artificial lipophilic membranes of two chamber dissolution-permeability system.

For generic drug development traditional (USP) dissolution tests have been used in the pharmaceutical industry to compare performance of different drug product formulations before or instead of conducting bioequivalence studies. Although dissolution tests provide a simple way of testing formulations, the in vivo predictive power of these tests are questionable. Namely, when a poorly water-soluble API is formulated to enhance its dissolution, additives, such as surfactants and polymers have an effect not only on dissolution profile, but also on flux through the membrane. The aim of this study was to represent the importance of simultaneous dissolution-absorption studies using MacroFLUX apparatus before conducting bioequivalence studies.

Pharmaceutical cocrystals have emerged as one of the potential strategies to enable supersaturation for poorly soluble drugs and as a result to improve their oral absorption and bioavailability . Flux across a membrane provides a better understanding of passive absorption of solutes from supersaturated solutions, since solute activity rather than concentration is the driving force. This study was aimed at investigating how supersaturation of model drug danazol released from its cocrystal in biorelevant media affects the trans-membrane flux of this low soluble compound.

Amorphous Solid Dispersions (ASD) of low soluble drugs has become one of the favorite technologies in attempt for improving gastro‐intestinal (GIT) absorption and as a result bioavailability of insoluble compounds. The goal of this study was to apply in situ concentration monitoring for quick assessment of degree and extent of supersaturation that can be achieved by amorphization of the drug. In addition the comparison of the flux through artificial lipophilic membrane from drug loaded below and above their amorphous solubility threshold was investigated.

The SDi2 (Surface Dissolution imaging) instrument combines high resolution UV/vis imaging with a USP IV type flow through cell to study drug product performance. Biorelevant buffer systems and pH shifts may be incorporated to generate meaningful data. The dual wavelength capability allows for the study of drug concentration in solution, and physical processes such as disintegration and swelling in a single experiment. In this study, a quantitative in vitro comparison of drug release between different dosage forms was linked to formulation composition.

Salt formation is often used to improve solubility of acidic drugs at low pH. When studying the dissolution of acidic active pharmaceutical ingredient (API) salt forms, results are often hard to interpret using a single technique due to their varying stability and eventual solid form conversion. Raman spectroscopy has been used in parallel with the Pion SDi2 to study the real-time surface dissolution of compacted diclofenac Na and monitor an associated solvent-mediated form transition.

Subcutaneous (SC) therapies have gained more importance over the years due to their favourable ability to administer chronic therapies in comparison to their intravenous (IV) counterparts. Furthermore, with the ageing of the world population, it is of particular importance to reduce the burden of the health services. Since SC formulations do not require supervision by medical professionals to be administered, they present an excellent alternative to the current intravenous therapies.
Even though the majority of SC formulations consist of biopharmaceuticals, some formulations contain a non-protein molecule as an Active Pharmaceutical Ingredient (API).

The Scissor is a new instrument designed to simulate the physiological conditions of the hypodermis, to be used as an in vitro model of the physical behaviour of biopharmaceutical formulations undergoing subcutaneous (SC) injection.
Often biopharmaceuticals are formulated under non-physiological conditions with the aim of improving stability and prolonging shelf-life. Biopharmaceuticals intended for SC injection are typically formulated at low pH to mitigate decomposition, and in the presence of various stabilising agents and excipients.

Insulin is a peptide hormone produced in the pancreas. It is used to regulate blood glucose levels by promoting the absorbance of glucose from the blood stream and inhibiting the production of glucose by the liver.

There is a strong patient preference for subcutaneous (SC) delivery of parenteral drugs. SC therapies are safer to administer and less time-consuming than intravenous (IV) therapies and they do not require supervision by medical professionals, making them
suitable for self-managed home care treatments.

A comprehensive validation study conducted using the SiriusT3 instrument has demonstrated that highly accurate and repeatable data are obtained for key physico-chemical parameters using sub milligram amounts for pKa and logP measurements and from as little as 2 mg for solubility measurements. The study compared results obtained from Pion standard assays with literature values and excellent agreement was demonstrated.

Understanding the ionisation properties of a molecule is an essential requirement for drug development. SiriusT3 technology provides the capability to perform pKa measurements in 15 minutes using only 5 µL of a 10 mM stock solution. This method requires that the molecule exhibits discernable UV absorption changes on ionisation and possesses an intrinsic aqueous solubility greater than 30 µM. Compounds having a lower aqueous solubility can be accommodated using a cosolvent assay.
The SiriusT3 Fast UV pKa method has been validated against results reported in the literature and produces results that are of comparable quality to those obtained by traditional methods. Measurement repeatability is typically within 0.01 pKa units. A complete summary of the data collected in this study is available on request.

Blank titrations enable calibration of the pH electrode using the Four-Plus method. The Four-Plus values describe the theoretical shape of the blank titration curve that best fit the experimental curve and are used to set up the pH concentration scale.

This application note describes how the Pion Cheqsol solubility assay and Log P measurements can give useful insights into the BCS class of your compound.

The determination of pKas outside of the range 3 – 11 using potentiometric methods can prove problematic, due to the high buffer capacity of water and the relatively poor performance of pH electrodes at the extremes of the pH range. Capillary electrophoresis methods also perform poorly in this range.
It is also true that predicted pKa values are less reliable at the extremes of the pKa range. This application note describes some experimental designs for the SiriusT3 which may be used to overcome these problems, giving reliable pKa values between 0.7 and >13.

The ionisation constant or pKa is a solution property of a compound. The formation of a precipitate during a pKa acid/base
titration therefore prevents the accurate measurement of pKa. However, drug-like molecules are often poorly soluble in water. In these cases, a cosolvent mixture comprising water and a water-miscible organic solvent can be used to enhance solubility. By performing titrations in several different solvent / water ratios, the pKas of water-insoluble compounds can be derived using the well-known Yasuda-Shedlovsky extrapolation.

An understanding of the dissolution and precipitation behaviour of active pharmaceutical ingredients is of fundamental importance in designing formulation approaches for successful drug delivery. The Pion GI Dissolution Assay has been designed as a formulation tool to conduct low volume, multi pH assays to give insight into how the dissolution of a drug is influenced by changes in pH1. By incorporating different excipients in the assay, methods of maintaining enhanced levels of drug in solution can be investigated to maintain supersaturation and avoid precipitation issues. Additionally, the assay can accommodate a lipid
sink to further mimic drug absorption.

Solubility is a key pharmaceutical parameter. For pharmaceuticals, the solubility in two types of media are important: aqueous based fluids such as the gastrointestinal tract fluid and blood, and lipid based media such as cell membranes and micelles.
Most biochemical and pharmacological processes occur in aqueous media and determining the solubility of a drug in an aqueous based medium is a very important part of drug development. This application note briefly introduces some relevant
terminology and methods of determining solubility.

The CheqSol method accurately determines the kinetic and intrinsic solubilities of ionizable compounds. It generates detailed information about the extent and duration of supersaturation and a pH-solubility profile from a single, highly automated assay which takes less than 2 hours. This application note provides a brief overview of the technique and should be read alongside Application Note 08/12, Solubility and Supersaturation —A Brief Introduction, which describes some terminology associated with solubility determination.

This Application Note presents an alternative approach – to dissolve the sample in a small volume of cosolvent before the
aqueous phase or octanol are added.

In their efforts to enhance the bioavailability of poorly soluble drugs in BCS Class II, formulators often work with amorphous forms, which are many times more soluble than crystals of the same substance. The problem is, how can the amorphous drug be preserved, even though its natural tendency is to crystallise? One way is to prepare it as a solid dispersion.

The ability of a drug to permeate biological membranes is influenced by log P, an important pharmaceutical parameter. It is described as the ratio of the concentration of compound dissolved in a lipid layer, which is usually modelled by octanol, over the concentration of compound dissolved in water.

This application note focuses on three solubility assays:
1. Screening assay
2. Shake-flask equilibrium assays
3. pH-metric solubility assay

This Application Note compares pKa values measured in the presence of sodium and potassium ions, and discusses the implications for dissolution measurement.

Pion has extensive experience in measuring pKa values of novel drugs for our Analytical Service customers. Where we know the compound’s structure, we use computational methods to predict the number of pKas and the type (acidic or basic); this information helps us to design optimal experiments.

The isoelectric point (pI) is the pH at which biological amphoteric molecules such as peptides and proteins carry no net electrical charge. Biopharmaceutical drug formulations that are intended for subcutaneous injection are often prepared at about pH 4 to enhance shelf life but when they are injected into the body the pH swiftly moves to 7.4. If the isoelectric point is between these pH values, there is increased risk of precipitation and aggregation after injection, which could diminish bioavailability.

The Pion InForm platform (figure 1) was used to determine the intrinsic dissolution rate (IDR) of ibuprofen and its sodium salt at pH 6.5. The IDR of a compound is the surface specific dissolution rate of a compound measured under the conditions of the study.

Biphasic dissolution is now fully supported in a commercial instrument. The inForm provides a robust protocol for this assay, as described below.

Controlled supersaturation is now fully supported in a commercial instrument. Pion inForm provides a robust protocol for this assay, as described below.

Lipolysis assays are now fully supported in a commercial instrument. Pion inForm provides robust protocols, as described below.

Biorelevant dissolution in simulated intestinal fluids is now supported in a commercial instrument. Pion inForm provides robust assay protocols, as described in the example below.

Controlled Supersaturation experiments on Pion inForm provide a way to create supersaturated solutions which can then be monitored to determine the time when precipitation starts, and the precipitation rate.

A PhysChem study was carried out using the Pion inForm, to observe the solubility, supersaturation, precipitation and dissolution behaviour of the compound.

Overcoming the difficulties posed by BCS Class II and IV APIs, where oral bioavailability is typically poor, is a challenge for modern formulation development. Although dissolution instrumentation is prevalent, most types of apparatus are not designed to simulate physiological conditions and their in vivo predictive power is poor. An instrument that has the ability to predict formulation behaviour in vivo would, therefore, be a useful tool for formulators looking to understand how their formulation was likely to perform in animal testing and clinical trials. The Pion inForm is an automated robotic, titrator that has the capability to test multiple formulation types using a variety of assays designed to mimic the dynamic chemical environment of the GI tract.

This poster reports on two biphasic studies of felodipine. In the first, partition rates were measured at concentrations above and below its amorphous solubility to understand the impact of different dose levels on absorption. In the second, solid dispersions of API of two different particle sizes were created in order to investigate dissolution‐limited aspects of drug absorption. Experiments were performed using Pion inForm, an instrument for biorelevant solubility and dissolution testing.

Measuring the dissolution performance of nanoparticle suspensions presents some practical challenges as (i) the rate of dissolution is often very fast, reaching maximum concentration within seconds and, (ii) depending on the concentration of the suspension, turbidity may be encountered. For ex-situ analytical techniques, such as HPLC, a fast sample collection rate and reliable phase separation is required in order to measure the kinetics of the dissolution process, which is often not achievable. Therefore an in-situ technique is preferable.

The selection of an appropriate salt form for a potential drug candidate is an opportunity to modulate its characteristics to improve bioavailability, stability and manufacturability. The intrinsic dissolution rate (IDR) and the dissolution profile of a free base and four complementary salts were investigated in order to understand the effect of the counterions on the dissolution of the API, using the Pion inForm.

Biphasic dissolution experiments can be used to study the lipid absorption of drugs and are performed using the Pion inForm platform (right). The Pion inForm contains dispensers for volumetrically dispensing reagents via capillaries into the measurement cell. For this study, 40 mL of an aqueous acetate-phosphate buffer was dispensed and adjusted to pH 6.5, after which 30 mL of decanol was added as a lipid phase. Stirring was continuous and at a constant rate of 100 rpm.

The SDI monitors dissolution from surfaces. It comprises a 2 mL flow cell, a pump, a lamp and a UV camera. A sample is placed in the flow cell and a Dissolution Medium (solution) is pumped through the cell.
If the sample absorbs UV light (most do), the camera will record images showing the build-up of sample as it dissolves.

The measurement services comprise a range of PhysChem and solid state assays which can be applied at many points in the drug development timeline. Our assays include screening analyses, “Gold Standard” definitive PhysChem assays, and formulation and early development studies.

Assay Expert combines the predictive power of ACD/Labs with the automation & experimental precision of the SiriusT3 instrument.

Pion Inc. is committed to excellence through innovation. Our in-house software development
team is dedicated to a continuous improvement program to enhance existing functionality and introduce new developments to the Pion software.

The Pion SDi2 (Surface Dissolution imaging) instrument combines high resolution UV/vis imaging with a USP IV type flow through cell to study drug product performance. Biorelevant buffer systems and pH shifts may be incorporated to generate meaningful data. The dual wavelength capability allows for the study of drug concentration in solution, and physical processes such as disintegration and swelling in a single experiment.
In this study, a quantitative in vitro comparison of drug release between different dosage forms was linked to formulation composition.

The biopharmaceutical market has grown rapidly in the past 30 years, principally in the last decade. This has been driven by the discovery of new molecules and innovative therapies. However, the way biopharmaceuticals behave immediately after administration is still largely unknown. The Pion Scissor is the first instrument designed to simulate the stress conditions and environmental transitions that a biopharmaceutical drug experiences upon injection into a subcutaneous (SC) environment.

SiriusT3 measures pKa, log P, log D and solubility of ionizable drugs and small molecules, requiring minimal amounts of sample. It also measures dissolution of ionizable and neutral compounds in volumes down to 1.5 mL. SiriusT3 instruments are used in labs that support drug discovery, crop science research, by universities, biochem and CROs.

The Pion inForm measures the kinetics of dissolution, absorption, controlled supersaturation and real-time precipitation under biorelevant conditions, while accommodating multiple dosage forms and sample types. Versatile options include our novel automated biphasic dissolution, solubility and lipolysis assays. The Pion inForm provides high quality support for formulation development and reflects the industry’s regulatory shift towards QbD.

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Bringing Solubility and Dissolution Data to Light

This technical note introduces devices that can be utilized for flux measurements in a systematic and reproducible manner. The small volume apparatus called μFLUX is compatible with Pion’s mini-bath (MB-8) and can be used on various stages of formulation development when amount of API and/or its formulations is limited while many permutations of different formulation strategies have to be investigated. The other device MacroFLUX is an absorption chamber insert into USP 1 or 2 dissolution bath vessels. Both apparati would allow assessment of complex interplay between solubility, permeability and dissolution rate in formulation development and would provide valuable tools for in vivo predictive in vitro studies.

Nanoparticle formulations of active pharmaceutical ingredient (API) are often made in the form of a suspension with addition of surfactants to prevent nanoparticles from aggregating. The concentration of dissolved API in the nanosuspension is often unknown and determining the solubility of API when nanosuspension is added to the assay media is challenging. This technical note will describe the use of Zero Intercept Method (ZIM) implemented in Au PRO™ software to resolve these issues.

The pKa determination by UV titration relies on the differences in molar absorptivity between charged and uncharged species present in solution. The traditional UV titration of a compound takes about 25–30 minutes. The fast UV titration method utilizes Pion’s linear universal buffer Prisma™ HT. It enables replacing a variable volume titrant addition with a constant volume addition that produces predictable pH change with each dispensed aliquot of KOH or HCl. This technical note demonstrates that reducing the number of titration points while keeping their uniform distribution along pH axis produces comparable results to the regular UV titrations while reducing the assay time to 7–10 minutes per titration. Additional potential benefit of fast titrations is that low-soluble compounds can stay supersaturated for a short period of time. That may enable aqueous pKa measurements for some low-soluble compounds that otherwise have to be determined only with the presence of cosolvent. It can also benefit compounds that are not stable and would decompose during the long assay.

Studying the permeation properties of formulations is crucial in all stages of dermal and transdermal formulation development. Most of the available methods suffer from being labor-intensive and having poor reproducibility. Skin PAMPA technology is a useful tool for the early stages of development as it is an easy-to-use, cost-effective, and standardized model with significantly lower variation compared to most of the available methods. This technical note provides an example of studying three commercially available diclofenac formulations using Skin PAMPA model.

Applying transdermal patches to deliver active pharmaceutical ingredients (API) through the human skin provides numerous advantages compared to traditional dosage forms. Therefore, more and more efforts are devoted to the development of these formulations. To help the evolution of the patches, Skin PAMPA provides a unique opportunity to continuously estimate the performance of the patch during the early stages of development. This can help the formulator test various combinations, aiming to reach the most promising matrix for each API.

Because of its well characterized fluid hydrodynamics, the rotating disk method is a useful tool for mechanistic dissolution studies. The disk intrinsic dissolution rate (DIDR) measurements have been used to characterize solid drugs, including studies of dissolution-pH rate profiles in the presence of buffers, complexing agents, and various excipients. It is currently debated at the FDA whether the DIDR method can be used to determine solubility class membership in the Biopharmaceutics Classification System, with encouraging early indications.

This work aimed to introduce an in vitro method for qualitatively estimating food effect in early stages of pre-formulation and formulation based on the differences in the flux through artificial lipophilic membranes of two chamber dissolution-permeability system.

For generic drug development traditional (USP) dissolution tests have been used in the pharmaceutical industry to compare performance of different drug product formulations before or instead of conducting bioequivalence studies. Although dissolution tests provide a simple way of testing formulations, the in vivo predictive power of these tests are questionable. The aim of this study was to represent the importance of simultaneous dissolution-absorption studies using MacroFLUX™ apparatus before conducting bioequivalence studies.

Feasibility study showing application the MacroFLUX to evaluate and predict the risk of drug-drug interaction based on the flux response.

A key challenge in formulation development is correlating data from traditional dissolution tests with in vivo outcomes. In this study, two proprietary dissolution technologies were utilized to investigate the effect of formulation differences on drug release for
immediate (IR) and extended (ER) release Metformin tablets.

The flux of several intraconazole formulations were compared to the commercially available product (Sporanox). It was demonstrated that data obtained with µFLUX correlated extremely well with animal studies.

This work demonstrates the ability of Skin PAMPA to differentiate and classify the effect of cosmetic solvents on permeation of 2 model compounds, SymWhite™ and Aminexil, and to provide a useful input for formulation development.

Novel device MacroFLUX™ that integrates absorption chamber into USP 2 dissolution bath was used to demonstrate that differences in bioequivalence study between benchmark brand name drug and its generic formulation could have been quantitatively predicted by comparing flux measurements for these formulations.

Prediction of the food effect on absorption of the drugs is challenging and requires expensive animal studies. This work shows that in vitro measurements using µFLUX device could predict food effect reducing number of animal testing.

This study was aimed at investigating how cocrystal coformers affect the trans-membrane flux in the in vivo relevant dissolution – permeability setup

The purpose of this study was to determine applicability and limitations of two in situ methods (spectroscopic UV-vis and potentiometric) in their ability to measure free drug concentration in the presence of nanoparticles.

The formulation development for a poorly water soluble antipsychotic drug aripiprazole is presented using µFluxTM apparatus, a technique, which, besides measuring dissolution follows the flux at the same time enabling to achieve better in vitro-in vivo correlation.

The purpose of this study was to determine applicability and limitations of this potentiometric technique to measure free drug concentration in the presence of nanoparticles.

This study was aimed at exploring the feasibility of conducting simultaneous dissolution testing of two actives, using a multi-channel UV-Vis fiber optic system and second derivative spectra, as an analytical technique to support real-time in vitro release profiling.

The goal of this study was to develop a method enabling simultaneous monitoring of dissolution of the drug product in the compendial apparatus at the same time providing the means to assess kinetic of API penetration into the absorption chamber separated from the dissolution vessel by a lipophilic membrane.

In this study, the potential of the FDS to differentiate between free drug and drug bound in micelles was investigated with the aim of real-time monitoring the concentration of free drug during in vitro lipolysis of lipid formulations.

In this study we will show that the free drug sensors can be used in media containing up to 5% surfactant and that the above mentioned issues can be satisfactory resolved. The products Brij-35 ® Tween 20 ® and Tween 80® were tested.

Purpose: To experimentally determine dissolution rate and solubility of a number of poorly soluble drugs with a new miniaturized method.

Conclusions: The miniaturized dissolution method is suitable to use also when measuring truly poorly soluble compounds and using biorelevant media. The IDR showed excellent correlation with the apparent solubility values, indicating that the IDR can be used as a substitute for measurement of solubility. Hence, the method allows rapid assessment of dissolution rate and solubility using a small amount of compound only. 

Purpose. The objective of the study was to investigate the properties of several of the polymorphs of sulfathiazole using a new miniaturized powder intrinsic dissolution rate (IDR) apparatus, and to relate the IDR values to solubility.

Conclusion.  This study successfully demonstrated the application of the new method to simultaneously determine two important properties of the polymorphs of sulfathiazole: (1) intrinsic dissolution rate, and (2) pH-dependent solubility.  Powder IDR measurements can be used in the early stages of drug development since they use up to 1000 times less API than traditional Wood’s rotating disk apparatus and are much faster. 

Purpose.  The goal of the study is to predict the pH-dependent permeability profiles of drugs in a Caco-2 assay, based on an in combo procedure using measured PAMPA permeability values and calculated Abraham (alpha, beta, pi, R, Vx) descriptors.

Conclusion.  The ability to predict with confidence how Caco-2 permeability will depend on the physicochemical properties of a drug is important in both planning measurements of practically-insoluble molecules and interpreting the results of difficult measurements.  The method we developed appears to be useful in saving cost, by avoiding poorly-designed assay protocols, and in some cases, altogether avoiding the need for the costly measurements.

Purpose. The objective was to investigate the feasibility of using a miniaturized disk intrinsic dissolution rate (IDR) apparatus to determine the Biopharmaceutics Classification System (BCS) solubility class while significantly reducing compound consumption comparing to traditional Wood’s apparatus. Additional goal was to develop an approach where IDR measurements performed in media of different buffer capacity could be compared.

Conclusion. The results demonstrate that using 100-fold less drug does not sacrifice the quality of the measurement, and lends support to an earlier study1 that the disk IDR measurement may possibly serve as a surrogate for the BCS solubility classification. API-sparing miniaturized IDR measurements can be done much earlier in the drug development cycle.

Purpose. A newly developed assay was applied for fast in vitro screening of the effect of various vehicles (e.g., 2-hydroxypropyl-b-cyclodextrin (HP-b-CD), polyethylene glycol 400 (PEG400, etc.) on solubility and absorption of sparingly soluble compounds.

Conclusion. A new in vitro PK method facilitates studying of the complex role excipients play in absorption. Sometimes, individual measurements of permeability and solubility, a task that is especially tedious for sparingly soluble compounds, can be avoided. This practical, low-cost, and relatively high-throughput UV-based assay incorporates the advances achieved in Double-Sink™ PAMPA and is demonstrated to be useful in early lead-investigation screening for formulation effects on absorption.

The permeability measurements were performed by ex vivo Franz diffusion cell method and a newly developed Skin-PAMPA model. Franz diffusion cell measurement is a commonly used research tool for studying diffusion through in vitro synthetic membranes or penetration through ex vivo human skin, while Skin-PAMPA is a recently published technology for the fast prediction of skin penetration. Transdermal preparations were investigated containing 2.64% concentrations of different SEs and/or TR, while the IBU concentration (5%) has been kept constant to be able to see the effect of penetration enhancers

The aim of this study was to compare drug permeation in Franz diffusion cells using porcine skin and in the Skin PAMPA model. Ibuprofen, caffeine and Uvinul A Plus (Table 1) were selected as the model permeants as they represent respectively, a lipophilic and hydrophilic skin permeant and a compound which resides largely on the surface of the skin.

The aim of this study was to evaluate applicability of Attenuated Total Reflection (ATR) UV probes to accurately measure highly concentrated solutions in real time with no need for dilution and solid separation.

Purpose. This research investigated the applicability and limitations of a novel approach for measuring intrinsic dissolution rates (IDR) of very small quantities of compounds introduced as powders to buffered solutions and compare these results to disk IDR obtained using the traditional Wood’s apparatus.

Conclusion. Powder IDR measurements can be used in the early stages of drug development, as they use up to 1000 times less API than the traditional Wood’s rotating disk apparatus and are much faster, too. Application of the powder dissolution method to compounds with solubility >1 mg/mL requires additional study.

Purpose.  The goal of this study was to measure the apparent solubility of a diverse series of poorly soluble compounds in four different biorelevant dissolution media (BDM, eg. FeSSIF, FaSSIF, and blanks for each) by simulating intestinal conditions to investigate the result in potential BCS classification.  The µDISS Profiler™ allowed simultaneous measurement of dissolution rate and solubility in small volumes of BDM.

Conclusion.  All seven compounds displayed higher solubility in FeSSIF than in the corresponding blank buffer. Increased solubility in the BDM resulted in an improved rating in the BCS for cinnarizine, felodipine, indomethacin, terfenadine from class II to class I.  Danazol and glibenclamide remained unchanged.       

Purpose. This research investigated the applicability and limitations of a novel approach for measuring intrinsic dissolution rates (IDR) of very small quantities of compounds introduced as powders to buffered solutions and compare these results to disk IDR obtained using the traditional Wood’s apparatus1.

Conclusion. Powder IDR measurements can be used in the early stages of drug development, as they use up to 1000 times less API than the traditional Wood’s rotating disk apparatus and are much faster, too. Application of the powder dissolution method to compounds with solubility >1 mg/mL requires additional study.

Purpose.  This study was conducted to assess the permeability of the blood-brain barrier (BBB) to drug-like compounds with a wide range of molecular properties, using the in situ brain perfusion technique in P-glycoprotein (Pgp) deficient [mdr1a(-/-)] mice, and to predict this permeability using an in combo PAMPA (in silico supported parallel artificial membrane permeability assay) model.

Conclusion.  The in situ brain perfusion measurements of drug-like molecules, in Pgp deficient mice, can be predicted by an in combo PAMPA method to a satisfactory degree, based on a training set of in situ BBB measurements.  The speed of the PAMPA method, and its substantial lower cost, compared to in vivo measurements, make it an attractive first-pass screening method for BBB passive permeability. 

Purpose.  The aim of the study was to assess how thin PAMPA membrane barriers could be made before they become too fragile or leaky through water pores.

Conclusion.  It was shown that antipyrine can have an elevated PAMPA permeability value (from 1 to 5 x10^-6 cm/s) in the plates with the thinnest barrier (BD), but it was clear that the plates were too leaky through water pores.  This would limit the application to lipophilic molecules.

Recently developed Zero Intercept Method (ZIM) enabling, for example, in situ concentration monitoring of free API being released from nanoparticles was applied to determine solubility and dissolution of gresiofulvin formulated as nanosuspension. The effect of formulation was also studied through miniaturized dissolution-permeability setup (µFLUX) to determine if nanosuspension formulation improves flux of the griseofulvin through artificial membrane.

In this study we intent to show that ISE’s can detect / quantify the BSA-drug binding and determine in real time the decrease in concentration of free drug after protein addition to a drug solution.

Purpose.  Most of the drug pKa values have been determined at 25°C, instead of physiologically-relevant 37°C.  The aim of this study is to develop a simple model to predict drug pKa values at 37oC from their corresponding 25oC values.  This is expected to improve the in vitro-in vivo correlation (IVIVC) in some cases, and get an improved understanding of the drug absorption process. 

Conclusion.  The model we developed is simple to apply to investigative dissolution rate studies done at 37oC, to mechanistic cellular studies, such as Caco-2, as well as to other physiological condition-based measurements. 

Purpose.  To optimize pH conditions for Caco-2 assay that allow de-convoluting and understanding various contributions to passive transport of drugs through the cell membrane. The pH and concentration effects on carrier-mediated/active transport were also studied.

Conclusion.  A novel approach of optimizing Caco-2 conditions based on predicted results enables the interpretation of difficult measurements with greater level of confidence. The developed approach saves costs, by avoiding poorly-designed assay protocols, and in some cases, avoiding the need for costly measurements.

This study was aimed at comparing the supersaturation ability of Soluplus® and Kollidon® VA 64 with low soluble compound Meloxicam as a model drug by using real time concentration monitoring and dissolution – permeability setup.

In this study we evaluated the applicability of universal potentiometric sensors to monitor concentration of API in situ for real food samples. It will be demonstrated that the measurements can be performed not only in liquid food (beer, wine and sodas) but also in suspended solid food such as noodles and steak and this without any sample preparation.

In the present study commercially available transdermal patches (3 nicotine, 2 fentanyl, 1 rivastigmine and 1 ketoprofen) are studied. Data are compared to the declared permeation speed that is indicated by the manufacturers.

Purpose. The salt form of an API (active pharmaceutical ingredient) may dissolve, partially or completely, to transient concentrations above equilibrium solubility levels.  The supersaturated solution may then precipitate as the free acid/base, sometimes coating the remaining input API or formulation, thus significantly modifying the subsequent dissolution rate.  The timeframe of supersaturation and potential precipitation events may have profound effects on bioavailability in vivo.  The aim of this study was to develop a practical and predictive in vitro powder and formulation dissolution method to monitor dissolution and concomitant precipitation processes in biorelevant media. 

Conclusions. This novel  in situ monitoring approach to in vitro powder and formulation dissolution/precipitation can provide a fundamental understanding of processes that may be relevant in vivo providing rational approach to formulation design and development. 

Purpose.  To prepare and test hot melt extrudates of Loratidine with Copovidone at 30% and 40% drug loading using a bench-top Dynisco laboratory mixing extruder (LME) at various temperatures. Dissolution behavior and solubility enhancement was tested using a small-volume in situ UV dissolution apparatus μDISS Profiler to collect concentration-time profiles in biorelevant media (e.g., FaSSIF and FeSSIF).

Conclusion. Temperature was an important process parameter in preparing amorphous solid dispersions of Loratidine with Copovidone at 30% or 40% API loading on the Dynisco LME. The μDISS Profiler allowed real-time concentration monitoring in small volumes of media thus providing a valuable tool for studying meta-stable solubility of amorphous form of API. 

Purpose.  Investigation of the transdermal drug delivery route has intensified recently for both novel and existing drug products. The aim of this work was to adapt the parallel artificial membrane permeability assay (PAMPA) for predicting skin penetration by employing an artificial membrane mimicking the stratum corneum layer of human skin.

Conclusions.  The Skin-PAMPA model predicts human skin permeability reasonably well, and because of its standardization potential and high-throughput nature it can be a valuable cost effective alternative to Franz cell studies for early skin penetration prediction. 

Purpose. The objective of the study was to develop the method of in situ concentration monitoring of free API being released from its nanosuspension without the need for separation of un-dissolved nanoparticles. The comparison of dissolution behavior of micronized and untreated naproxen (API) powder with kinetics of free API release from nano- and microsuspensions was also the goal of this work.

Conclusion. Developed method allowed in situ measurement of free API concentration in solution in the presence of nanoparticles. Solubility of naproxen was the same within several standard deviations between all forms of naproxen studied. However dissolution from nanoparticles was practically instantaneous compared to the case of microsuspension or powders.

Purpose. This study aimed to investigate the accuracy of software to predict the ionization constants, pKa for a variety of flavonoids.

Conclusion. Flavonoids exhibit several challenges to accurate pKa measurement, including low solubility and potential oxidative degradation. Cosolvents ensured that the compounds were completely in solution during the titration. While the assignments made herein are tentative, they suggest that the beta hydroxy group may undergo internal hydrogen bonding that may be incorporated into some commercially available software programs, thus providing better agreement between measured and predicted values. Future work will focus on investigating some of the underlying chemistry further.

Cocrystals are one more tool of formulation scientist to increase solubility of insoluble drug. This study illustrates use of flux measurements to investigate if cocrystal formulations of danazol can improve its bioavailability

This case study demonstrates ability of in situ concentration monitoring in the simulated mucus fluid as well as ability of µFLUX to reveal if drugs stay supersaturated in the mucus simulated environment

Case studies demonstrating capability of µDISS Profiler, µFLUX apparatus and AuPRO software to determine the degree and extent of supersaturation of amorphous forms and differentiate them from liquid-liquid phase separation.

It has been shown that a miniaturized two‐stage in vitro dissolution test can be used to understand why some low‐soluble weak basic drugs show reduced or highly variable absorption when co‐administered with pH‐modifying agents. The goal of this study was to demonstrate that an absorption chamber combined with USP I and II dissolution apparatus can be used to study similar drug‐drug interactions (DDI) of the final dosage forms.

It was hypothesized and then demonstrated that small intestinal mucus layer could stabilize supersaturated state of otherwise precipitating low solubility drugs. It was also concluded that flux measurements provide more in‐depth understanding of supersaturated systems than solute concentration measurements alone. This study used miniaturized dissolution – permeation apparatus (μFLUX) to compare flux of carvedilol through artificial membranes from a simple buffer system as well as from media simulating the mucus layer and/or containing solubilizing excipients like hydroxypropyl‐ß‐cyclodextrin.

It was demonstrated that flux measurements provide more in-depth understanding of supersaturated systems than solute concentration measurements alone. This study used miniaturized dissolution – permeation apparatus (μFLUX) to compare flux of itraconazole (Figure 1) from several formulations for which in-vivo rat PK data were available. The goal of the study was to evaluate the formulation benchmarking ability of the instrumental setup.

BASF Pharma Ingredients and Services offers our solutions-oriented Skin Delivery Platform to formulators of OTC and Rx topical products. This platform provides insights and materials to meet needs in Topical Drug Delivery, Mildness, Wound Care and Skin Sensory. In this work, Topical Drug Delivery is highlighted in a joint study with Pion, Inc. to evaluate the permeability of an API (sodium
ibuprofen) across an artificial skin-mimetic membrane assisted by various dermatology excipients as a means to assess their use as skin penetration enhancers for topical application. Three broad classifications of materials were tested, emollients as the classical penetration enhancer, as well as solvents and emulsifiers for use in a wide variety of topical product forms.

Up till present the use of universal potentiometric sensors in surfactant containing media was problematic. Typical issues arising are: slow response, limited sensitivity and short lifespan. In this study we will show that the free drug sensors can be used in media containing up to 5% surfactant and that the above mentioned issues can be satisfactory resolved. The products Brij-35 ® Tween 20 ® and Tween 80® were tested.

The timeframe of supersaturation and potential precipitation events may have profound effects on bioavailability. The aim of this study was to develop a practical, easily standardized and predictive in vitro dissolution method to monitor powder/formulation dissolution and concomitant precipitation processes in biorelevant media dynamically being changed from simulated gastric to simulated intestinal fluid. The importance of such API-sparing, two-stage, in vitro microdissolution tests to study drug-drug interaction in the case of pH-modifying agents was reported recently.

Development strategies for insoluble compounds require not only measurement of solubility enhancements achieved through formulation but also assessment of the effect a formulation has on permeability. An new dissolution-permeability measurement platform (µFLUX™) allows simultaneous monitoring of both effects thereby providing an in vitro path to early in vivo predictive biorelevant absorption testing.

A newly developed 96-well based assay was applied for fast in vitro screening of the effect of various formulation vehicles, as well as micronization and micelle formation on relative absorption enhancement for sparingly soluble compounds using artificial membranes.

Determining concentration of API released from nanoparticles presents a challenge as conventional solid separation techniques become unsuitable while nano-scale size of the particles influences the UV spectrum for UV-based techniques. A Zero Intercept Method (ZIM) presented in this work overcome these challenges allowing in situ concentration monitoring of free API as it is being released from nanoparticles.

Purpose
Using the skin as absorption site presents unique challenges that have facilitated the progression of transdermal drug delivery in the past decades. Efforts in drug research have been devoted to find a quick and reproducible model for predicting the skin penetration of molecules, because the in vitro or in vivo animal models are expensive, labor-intensive and suffer from poor reproducibility.
The Parallel Artificial Membrane Permeability Assay (PAMPA) 1 has been extended for prediction of transdermal penetration by developing the “skin-mimetic” artificial membrane 2. Having a high standardization potential and being a high throughput method, PAMPA can become an ideal model for prediction of skin penetration in early stages of drug development. In the present study commercially available transdermal patches (3 nicotine, 2 fentanyl, 1 ketoprofen) are studied. Data are compared to the declared permeation speed that is indicated by the manufacturers.

Purpose.  Transdermal delivery has facilitated the development of new drugs during the last few decades.  This work evaluated the interlaboratory performance of Skin PAMPA measurements conducted at Pion and by a well-known pharmaceutical supplier.

Conclusions.  As previously reported, Skin PAMPA measurements was highly correlated against Franz cell measurements (human epidermis) using fifteen different APIs.  The Skin PAMPA measurements of seven test compounds as performed in two different labs was in good agreement.  And lastly, both Skin PAMPA and the Franz cell method could easily distinguish between the API permeability in four different formulations.  These observations continue to demonstrate the potential utility of this new technique for rapid screening in a cost effective manner. 

Purpose.  To prepare and test hot melt extrudates of loratidine or piroxicam with copovidone polymers to improve the API solubility.  A bench-top Dynisco laboratory mixing extruder (LME) was used for preparation of the materials at various temperatures.  Dissolution behavior and solubility enhancement was tested using a small-volume in situ UV dissolution apparatus (μDISS Profiler) to collect concentration-time profiles in biorelevant media such as FaSSIF and FeSSIF.

Conclusions.  The supersaturation of piroxicam hot melt extrudates was quasi-stable for more than 24 hours at 3.5 times the solubility of the neat API.  Loratidine extrudates also exhibited a potential for supersaturation as well.  The µDISS Profiler provided concentration-time profiles with high data density without precipitation artifacts caused by liquid sampling.

Purpose. Solid dispersion technology is used to create amorphous APIs with enhanced solubility potentially leading to improved bioavailability. The objective of the study was to monitor dissolution and precipitation behavior of supersaturating solutions of low soluble compounds. Solubility enhancement was tested using a small-volume in situ UV dissolution apparatus μDISS Profiler™ (Pion Inc.) by collecting concentration-time profiles in biorelevant media (e.g., FaSSIF and FeSSIF).

Conclusions. Hot melt extrudates with Copovidone provide opportunity to improve bioavailability of low soluble compounds. The μDISS Profiler allows real-time concentration monitoring of limited amount of material in small volumes of media thus providing a valuable tool for studying meta-stable solubility of amorphous form of API.

Purpose. This work studied the applicability of a recently introduced skin-mimetic artificial membrane permeability model (Skin PAMPA) to differentiate between topical pharmaceutical formulations. The Skin PAMPA results were compared with data obtained from in vitro Franz cell permeability measurements.

Conclusion. The new formulation is demonstrated to be superior in delivering ibuprofen through a skin barrier compared with the commercial benchmark. The Skin PAMPA model can be used with topical formulations to differentiate their ability for transdermal delivery of active pharmaceutical ingredients. Standardization potential and the high-throughput nature of Skin PAMPA can be a valuable cost effective compliment to Franz cell permeability experiments for early skin penetration prediction and topical formulation development.

Purpose. This was aimed at understanding the supersaturation ability of Soluplus with Carbamazepine as a model drug by using real time concentration monitoring.

Conclusion. The data suggests that Soluplus maintained the supersaturation of CBZ in simulated media for longer period from the solid solutions. The μDISS Profiler can be used to measure the real-time concentrations of limited amount of drugs for investigating the supersaturation phenomenon.

Purpose. Formation of an API (active pharmaceutical ingredient) salt is a common technique for improving the dissolution characteristics and supersaturation of a poorly soluble drug. The supersaturated solution may then precipitate as the free acid or base. The aim of this study was to evaluate the practicality of combining real-time concentration monitoring with fiber optic spectroscopy and powder x-ray diffraction (PXRD) to provide an assessment of salt disproportionation and precipitation.

Conclusions. Combining real time in situ monitoring with solid state characterization can provide the preformulation or formulation scientist with a more complete understanding of processes that may suggest drug formulation and development strategies to improve the oral absorption window for a poorly soluble AP

Purpose.  The objective of the study was to predict human jejunal permeability, Peff, and absorption, %Fa, for a series of fluoroquinolones, using a biophysical model based on measured Caco-2 permeability.  Values of Peff have not been reported for these compounds, and not all of the compounds have reported human absorption values.

Conclusion.  Estimates of Peff can be predicted by the biophysical model. From these values, the human absorption may be calculated.  Where absorption comparisons were possible, the agreement was acceptably good.

Purpose. A newly developed device was applied to assess the feasibility of performing in situ UV concentration monitoring experiments in 96-well microtitre plate format.

Conclusion.  The study confirmed the feasibility of performing in situ dissolution and solubility monitoring in 96-well plate that was not possible before. In addition to high throughput solubility determination, other critical studies such as salt dissolution screening, dissolution/solubility determination in biorelevant media, solubility-excipient screening and others can be performed much earlier in the drug discovery saving costs by dramatically reducing required amount of compounds and expensive reagents.