Small Volume Dissolution Testing as a Powerful Method during Pharmaceutical Development

Effect of basket mesh size on the hydrodynamics of a partially filled (500 mL) USP rotating basket dissolution testing Apparatus 1

The USP Rotating Basket Dissolution Testing Apparatus 1 is listed in the USP as one of the tools to assess dissolution of oral solid dosage forms. Baskets of different mesh sizes can be used to differentiate between dissolution profiles of different formulations. Here, we used Particle Image Velocimetry (PIV) to study the hydrodynamics of the USP Apparatus 1 using baskets with different mesh openings (10-, 20- and 40-mesh) revolving at 100 rpm, when the vessel was filled with 500 mL. The velocity profiles throughout the liquid were found to vary significantly using baskets of different mesh sizes, typically increasing with increased size of the opening of the basket mesh, especially for axial and radial velocities. This, in turn, resulted in a significantly different flow rate through the basket, which can be expected to significantly impact the dissolution rate of the drug product. A comparison between the results of this work with those of a previous study with a 900-mL fill volume (Sirasitthichoke et al., Intern. J. Pharmaceutics, 2021, 607: 120976), shows that although the hydrodynamics in the USP Apparatus 1 changed with fill level in the vessel, the flow rate through the basket was not significantly affected. This implies that tablets dissolving in the two systems would experience similar tablet-liquid medium mass transfer coefficients, and therefore similar initial dissolution rates, but different dissolution profiles because of the difference in volume.

In Vitro Dissolution and Permeability Testing of Inhalation Products: Challenges and Advances

In vitro dissolution and permeability testing aid the simulation of the in vivo behavior of inhalation drug products. Although the regulatory bodies have specific guidelines for the dissolution of orally administered dosage forms (e.g., tablets and capsules), this is not the case for orally inhaled formulations, as there is no commonly accepted test for assessing their dissolution pattern. Up until a few years ago, there was no consensus that assessing the dissolution of orally inhaled drugs is a key factor in the assessment of orally inhaled products. With the advancement of research in the field of dissolution methods for orally inhaled products and a focus on systemic delivery of new, poorly water-soluble drugs at higher therapeutic doses, an evaluation of dissolution kinetics is proving crucial. Dissolution and permeability testing can determine the differences between the developed formulations and the innovator’s formulations and serve as a useful tool in correlating in vitro and in vivo studies. The current review highlights recent advances in the dissolution and permeability testing of inhalation products and their limitations, including recent cell-based technology. Although a few new dissolution and permeability testing methods have been established that have varying degrees of complexity, none have emerged as the standard method of choice. The review discusses the challenges of establishing methods that can closely simulate the in vivo absorption of drugs. It provides practical insights into method development for various dissolution testing scenarios and challenges with dose collection and particle deposition from inhalation devices for dissolution tests. Furthermore, dissolution kinetic models and statistical tests to compare the dissolution profiles of test and reference products are discussed.

A microfluidic-based approach to investigate the inflammatory response of macrophages to pristine and drug-loaded nanostructured hydroxyapatite

The in vitro biological characterization of biomaterials is largely based on static cell cultures. However, for highly reactive biomaterials such as calcium-deficient hydroxyapatite (CDHA), this static environment has limitations. Drastic alterations in the ionic composition of the cell culture medium can negatively affect cell behavior, which can lead to misleading results or data that is difficult to interpret. This challenge could be addressed by a microfluidics-based approach (i.e. on-chip), which offers the opportunity to provide a continuous flow of cell culture medium and a potentially more physiologically relevant microenvironment. The aim of this work was to explore microfluidic technology for its potential to characterize CDHA, particularly in the context of inflammation. Two different CDHA substrates (chemically identical, but varying in microstructure) were integrated on-chip and subsequently evaluated. We demonstrated that the on-chip environment can avoid drastic ionic alterations and increase protein sorption, which was reflected in cell studies with RAW 264.7 macrophages. The cells grown on-chip showed a high cell viability and enhanced proliferation compared to cells maintained under static conditions. Whereas no clear differences in the secretion of tumor necrosis factor alpha (TNF-α) were found, variations in cell morphology suggested a more anti-inflammatory environment on-chip. In the second part of this study, the CDHA substrates were loaded with the drug Trolox. We showed that it is possible to characterize drug release on-chip and moreover demonstrated that Trolox affects the TNF-α secretion and morphology of RAW 264.7 ​cells. Overall, these results highlight the potential of microfluidics to evaluate (bioactive) biomaterials, both in pristine form and when drug-loaded. This is of particular interest for the latter case, as it allows the biological characterization and assessment of drug release to take place under the same dynamic in vitro environment.

Design and Development of Solid SMEDDS and Liquisolid Formulations of Lovastatin, for Improved Drug Dissolution and In vivo Effects-a Pharmacokinetic and Pharmacodynamic Assessment

Lovastatin (Lov) is a lipid-lowering agent, with 5% bioavailability (BA) due to extensive first pass metabolism and poor solubility. To enhance dissolution and in vivo effects, Lov solid self microemulsifying drug delivery system (SMEDDS) and liquisolid systems were developed and evaluated to select superior one. Solubilities were determined in oils, surfactants, and cosurfactants. Ternary phase diagrams were constructed and selected the one which showed maximum emulsion zone. In vitro dissolution, DSC, SEM and PXRD studies were used to characterize the developed formulations. In vivo studies were conducted on optimal formulations in wistar rats. Based on solubilities, Capmul PG8 and Capmul MCM were preferred as oils, Labrasol and Transcutol P as surfactant and cosurfactant. Here, Syloid XDP carrier showed better adsorption capacity among others, hence was used in optimal solid SMEDDS (SX) and liquisolid (LS) formulations. Dissolution study results showed significant improvement in release when compared to pure drug. DSC, SEM, and PXRD results indicated the loss of drug crystallinity in optimal formulations. In pharmacokinetic (PK) study, SX and LS showed 2.57 and 1.43 fold improvements in AUC, when compared to that of coarse suspension (CS). In pharmacodynamic (PD) study, hyperlipidemia was induced by Triton X-100. CS and LS treatments showed a decline in hyperlipidemic levels at 4 h. But, SX-treated group showed early onset of decline at 2 h. Further, the duration of anti-hyperlipidemia was at least 12 h extra when compared to CS and LS. This study confirmed the superiority of SX over LS in PK and PD effects.

Embedding a Sensitive Liquid-Core Waveguide UV Detector into an HPLC-UV System for Simultaneous Quantification of Differently Dosed Active Ingredients during Drug Release

Individual dosing of pharmaceutics and personalized medicine have become important with regard to therapeutic safety. Dose adjustments, biorelevant drug release and combination of multiple active substances in one dosage form for the reduction in polymedication are essential aspects that increase the safety and acceptance of the patient’s pharmacotherapy. Therefore, not only innovative drug products but also new analytical methods are needed during the drug development phase and for quality control that can simultaneously determine different active ingredients and cover wide concentration ranges. We investigated a liquid-core waveguide UV absorbance flow cell detector coupled to an existing HPLC-UV system. A Teflon AF 2400 capillary tubing of 20 cm length was connected in series to the HPLC flow line and enabled a lower limit of quantification of 1 ng/mL pramipexole (increase in sensitivity by 20 compared to common 0.9 cm flow cells). This allowed the low-concentration of pramipexole and the higher concentrations of levodopa and benserazide occurring during drug release to be determined in a single chromatographic run within 22.5 min.

Performance Evaluation of Montelukast Pediatric Formulations: Part I-Age-Related In Vitro Conditions

This study aimed to explore the potential of biopharmaceutics in vitro tools to predict drug product performance in the pediatric population. Biorelevant dissolution set-ups were used to predict how age and medicine administration practices affect the in vitro dissolution of oral formulations of a poorly water-soluble compound, montelukast. Biorelevant age-appropriate dissolution studies of Singulair^® (granules and chewable tablets) were conducted with the µDISS profiler™, USP 4 apparatus, USP 2 apparatus, and mini-paddle apparatus. Biorelevant simulating fluids representative of adult and pediatric conditions were used in the dissolution studies. The biorelevant dissolution conditions were appropriately selected (i.e. volumes, transit times, etc.) to mimic the gastrointestinal conditions of each of the subpopulations tested. Partial least squares regression (PLS-R) was performed to understand the impact of in vitro variables on the dissolution of montelukast. Montelukast dissolution was significantly affected by the in vitro hydrodynamics used to perform the dissolution tests (µDISS profiler™: positive effect); choice of simulation of gastric (negative effect) and/or intestinal conditions (positive effect) of the gastrointestinal tract; and simulation of prandial state (fasted state: negative effect, fed state: positive effect). Age-related biorelevant dissolution of Singulair^® granules predicted the in vivo effect of the co-administration of the formulation with applesauce and formula in infants. This study demonstrates that age-appropriate biorelevant dissolution testing can be a valuable tool for the assessment of drug performance in the pediatric population.

Exploration of Neusilin® US2 as an Acceptable Filler in HPMC Matrix Systems-Comparison of Pharmacopoeial and Dynamic Biorelevant Dissolution Study

Modern pharmaceutical technology still seeks new excipients and investigates the further use in already known ones. An example is magnesium aluminometasilicate Neusilin^® US2 (NEU), a commonly used inert filler with unique properties that are usable in various pharmaceutical fields of interest. We aimed to explore its application in hypromellose matrix systems (HPMC content 10–30%) compared to the traditionally used microcrystalline cellulose (MCC) PH 102. The properties of powder mixtures and directly compressed tablets containing individual fillers NEU or MCC, or their blend with ratios of 1.5:1, 1:1, and 0.5:1 were investigated. Besides the routine pharmaceutical testing, we have enriched the matrices’ evaluation with a biorelevant dynamic dissolution study and advanced statistical analysis. Under the USP apparatus 2 dissolution test, NEU, individually, did not provide advantages compared to MCC. The primary limitations were the burst effect increase followed by faster drug release at the 10–20% HPMC concentrations. However, the biorelevant dynamic dissolution study did not confirm these findings and showed similarities in dissolution profiles. It indicates the limitations of pharmacopoeial methods in matrix tablet development. Surprisingly, the NEU/MCC blend matrices at the same HPMC concentration showed technologically advantageous properties. Besides improved flowability, tablet hardness, and a positive impact on the in vitro drug dissolution profile toward zero-order kinetics, the USP 2 dissolution data of the samples N75M50 and N50M50 showed a similarity to those obtained from the dynamic biorelevant apparatus with multi-compartment structure. This finding demonstrates the more predictable in vivo behaviour of the developed matrix systems in human organisms.

A Potential Alternative Orodispersible Formulation to Prednisolone Sodium Phosphate Orally Disintegrating Tablets

The orally disintegrating tablet (ODT) has shown vast potential as an alternative oral dosage form to conventional tablets wherein they can disintegrate rapidly (≤30 s) upon contact with saliva fluid and should have an acceptable mouthfeel as long as their weight doesn’t exceed 500 mg. However, owing to the bitterness of several active ingredients, there is a need to find a suitable alternative to ODTs that maintains their features and can be taste-masked more simply and inexpensively. Therefore, electrospun nanofibers and solvent-cast oral dispersible films (ODFs) are used in this study as potential OD formulations for prednisolone sodium phosphate (PSP) that is commercially available as ODTs. The encapsulation efficiency (EE%) of the ODFs was higher (≈100%) compared to the nanofibers (≈87%), while the disintegration time was considerably faster for the electrospun nanofibers (≈30 s) than the solvent-cast ODFs (≈700 s). Hence, accelerated release rate of PSP from the nanofibers was obtained, due to their higher surface area and characteristic surface morphology that permitted higher wettability and thus, faster erosion. Taste-assessment study using the electronic-tongue quantified the bitterness threshold of the drug and its aversiveness concentration (2.79 mM). Therefore, a taste-masking strategy would be useful when further formulating PSP as an OD formulation.

Similarity of dissolution profiles from biorelevant media: Assessment of interday repeatability, interanalyst repeatability, and interlaboratory reproducibility using ibuprofen and ketoconazole tablets

Biorelevant media are increasingly being employed as dissolution media in drug development, including in smaller volumes than 900ml and under non-sink conditions. The objectives were to assess interday repeatability, interanalyst repeatability, and interlaboratory reproducibility of dissolution profiles from biorelevant media, as well as to assess the impacts of biorelevant media production method and biorelevant medium volume on dissolution profiles. Ibuprofen and ketoconazole tablets were subjected to dissolution testing in 500ml, 300ml, and 40ml of fasted state simulated gastric fluid (FaSSGF), fed state simulated gastric fluid (FeSSGF), fasted state simulated intestinal fluid version 2 (FaSSIF-V2), and fed state simulated intestinal fluid version 2 (FeSSIF-V2). f₂ was used to assess repeatability and reproducibility of dissolution profiles. Results indicate favorable interday repeatability (83 of 88 comparisons were similar), favorable interanalyst repeatability (19 of 21 comparisons were similar), and favorable interlaboratory reproducibility (10 of 14 comparisons were similar) of dissolution profiles from biorelevant media, with commercial media showing greater interlaboratory reproducibility than 'from scratch' media. However, biorelevant medium production had low impact on profiles when one analyst conducted all medium preparations and study procedures at one location. Additionally, biorelevant media detected differences when products were not similar. Overall, biorelevant media showed favorable repeatability and reproducibility performance.

BCS-based biowaivers: Extension to paediatrics

A BCS-based biowaiver allows extrapolation of drug product bioequivalence (when applicable) based on the BCS class of the drug and in vitro dissolution testing. Drug permeability and solubility considerations for adult BCS might not apply directly to paediatric subpopulations and bridging of adult and paediatric formulations should be undertaken with caution. The aims of this study were to: (i.) identify compounds which would change drug solubility classification in the paediatric population, and (ii.) to assess the risk of extending BCS-based biowaiver criteria into paediatric products of these compounds. Amoxicillin, prednisolone, and amlodipine were selected as the model compounds. Dissolution studies of IR formulations of these compounds were conducted with USP II (paddle) and mini-paddle apparatus, in media of three pHs (pH 1.2, 4.5 and 6.8). Three dissolution setups were tested: (1) 'typical' BCS-based biowaiver conditions, (2) "BE" setup derived from BE study protocols (volume: 250 mL), and (3) "paediatric" setup based on representative volume for the paediatric population (50 mL). Results revealed that extension of regulated BCS-based biowaiver criteria for paediatric application is not as simple as scaling down volumes. It was further shown that BCS-based biowaiver criteria should not be applied when there is the risk of change of the drug solubility class, from the adult to paediatric populations. A deeper knowledge of the paediatric gastrointestinal environment is still lacking and would assist in refining the biopharmaceutical tools needed to appropriately evaluate formulation performance across age groups. This would potentially reduce the number of clinical studies required and speed up formulation development.

Synthesis and characterization of meloxicam eutectics with mandelic acid and saccharin for enhanced solubility

Meloxicam (MLX) is a non-steroidal anti-inflammatory which is practically insoluble in water, requiring high concentrations to reach therapeutic levels and causing frequently gastrointestinal effects. In this way, the aim of this study was to synthesize two eutectic mixtures of MLX with mandelic acid (MND) and saccharin (SAC) by liquid-assisted grinding resulting in a multicomponent material with enhanced solubility. Mixtures were studied in different stoichiometric and eutectic point was found for each eutectic by Binary phase diagram and Tamman's triangle, with 0.33 molar fraction of MLX for SAC and MND. Eutectics were characterized by thermoanalytical techniques (TG-DSC, EGA, DSC, and DSC microscopy), infrared spectroscopy, and X-ray powder diffraction. Thermal behavior was studied and videos of the materials being heated were available. A polymorphic transition was discovered and studied for MLX-MND eutectic. Each new system was evaluated by solubility, dissolution, and hygroscopicity tests. Eutectics showed an increase in solubility of 1.7× (MLX-MND1), 3.1× (MLX-MND2), and 1.3× (MLX-SAC) with slower dissolution profile when compared with MLX. All new solid forms showed high hygroscopicity at 98% relative humidity with 27.9 and 58.9% increase in mass at day four for MLX-SAC and MLX-MND, deliquescence occurs at day 6. The experiments and analysis in this study help to understand the behavior of eutectics and evaluate them as an approach to modify properties in drugs.

FDM-printed pH-responsive capsules for the oral delivery of a model macromolecular dye

To this day, the oral delivery of biomacromolecules remains a major developmentally-oriented challenge. A combinatorial approach was followed at this study, to formulate an efficient carrier for the in vitro delivery of a model macromolecule, fluorescein isothiocyanate-dextran 4 kDa (FD4). The model macromolecule was formulated in a self-assembling peptide hydrogel (ac-(RADA)₄-CONH₂), prior to deposition in a hydroxypropyl methylcellulose-phthalate (HPMCP)-based 3D-printed capsule. Loading of FD4 was investigated for potential alterations on the structural (AFM) and gelling properties of the peptide carrier. Thermal analysis and morphological properties of the 3D-printed capsules were assessed by TGA, DSC and microscopy studies. For the peptide hydrogel, similar release profiles of FD4 were recorded in simulated gastric fluid pH 1.2 and phosphate buffer saline pH 7.4, indicating the need for a structural barrier, to protect the peptide carrier from the acidic environment of the stomach. The pH responsive character of the HPMCP-based capsule was evidenced in the release profiles of FD4 in a sequence of release media, i.e. simulated gastric fluid pH 1.2, simulated intestinal fluid pH 6.8 and phosphate buffer saline pH 7.4. The results supported the combinatorial formulation approach as a promising system for the efficient oral delivery of biomacromolecules.

Biorelevant intrinsic dissolution profiling in early drug development: Fundamental, methodological, and industrial aspects

Intrinsic dissolution rate (IDR) is the surface specific dissolution rate of a drug. In early drug development, this property (among other parameters) is measured in order to compare different polymorphs and salt forms, guide formulation decisions, and to provide a quality marker of the active pharmaceutical ingredient (API) during production. In this review, an update on different methods and small-scale techniques that have recently evolved for determination of IDR is provided. The importance of biorelevant media and the hydrodynamic conditions of dissolution are also discussed. Different preparation techniques for samples are presented with a focus on disc, particle- and crystal-based methods. A number of small-scale techniques are then described in detail, and their applicability domains are identified. Finally, an updated industrial perspective is provided about IDR's place in the early drug development process.

Stability and compatibility of Basmisanil granules co-administered with soft food

Co-administration of solid oral dosage forms with soft food or beverages is commonly used to facilitate administration and to improve compliance in the paediatric and geriatric population and in patient groups with swallowing difficulties. The present case study was conducted to investigate the compatibility, stability and dissolution of Basmisanil administered as granules mixed with different soft food matrices. The data were generated to justify dosing instructions, according which Basmisanil should be sprinkled on or mixed with one tablespoon of soft food to aid swallowing. Different soft food types were selected to cover a broad range of various food components (e.g. fat, protein, carbohydrates, fiber and water) and pH. Active content and degradation products of the active substance were determined after mixing the granules with the semisolid food matrix and after two hours of storage under ambient conditions, respectively. In-vitro dissolution tests of granule/food mixtures were also conducted. Furthermore, the stability of the API polymorph was evaluated. Basmisanil shows good chemical stability when the granules are mixed with soft food and consumed within two hours. No polymorphic conversion (anhydrate to monohydrate) could be detected in the granule/food mixtures after preparation and after storage up to 24 h. The in-vitro dissolution of the API from the granules was not adversely affected by the presence of the food matrix. All results were comparable regardless of the tested food matrix. The results do not prohibit the administration of the granules with soft food to the patient.

Small volume method for drug release screening using ultrasonic agitation

Drug release testing plays a major role along all parts of the dosage form development and manufacturing process. However, official methods to perform this type of testing are often resource intensive and require highly specialized facilities. Affordable and accessible methods for studying drug release behavior are currently lacking. This work presents a small volume approach to solid dissolution and drug release testing of solid dosage forms using ultrasonic agitation. Cavitation and acoustic streaming were generated by a microprobe horn delivering a 40 kHz acoustic signal into a 50 mL test vessel. These two phenomena resulted in breakdown of and release of drug from tablet samples. Prednisone Performance Verification Tablets were used as model tablets to study the effect of system parameters on the drug release process. The effects of these parameters on the acousto-hydrodynamic environment were studied using streak photography and hydrophone measurements. Drug release behavior showed a slow/fast threshold transition separated by a highly variable regime as a function of the system parameters. Observations from drug release experiments and results from acoust-hydrodynamic characterization experiments suggested that this transition is dominated by acoustic streaming. This method represents a screening method to probe relative differences in dosage form composition and acts as a complimentary approach to official testing methods. The small volume format of this test has potential applications in the study of drug release properties from low-dose and novel solid dosage forms as well as reduced cost and increased accessibility of release testing for post-manufacturing tablet quality screening, a current need in low- and middle-income countries.

Computational hydrodynamic comparison of a mini vessel and a USP 2 dissolution testing system to predict the dynamic operating conditions for similarity of dissolution performance

The hydrodynamic characteristics of a mini vessel and a USP 2 dissolution testing system were obtained and compared to predict the tablet-liquid mass transfer coefficient from velocity distributions near the tablet and establish the dynamic operating conditions under which dissolution in mini vessels could be conducted to generate concentration profiles similar to those in the USP 2. Velocity profiles were obtained experimentally using Particle Image Velocimetry (PIV). Computational Fluid Dynamics (CFD) was used to predict the velocity distribution and strain rate around a model tablet. A CFD-based mass transfer model was also developed. When plotted against strain rate, the predicted tablet-liquid mass transfer coefficient was found to be independent of the system where it was obtained, implying that a tablet would dissolve at the same rate in both systems provided that the concentration gradient between the tablet surface and the bulk is the same, the tablet surface area per unit liquid volume is identical, and the two systems are operated at the appropriate agitation speeds specified in this work. The results of this work will help dissolution scientists operate mini vessels so as to predict the dissolution profiles in the USP 2, especially during the early stages of drug development.

Analytical technologies for real-time drug dissolution and precipitation testing on a small scale

Objectives

This review focuses on real-time analytics of drug dissolution and precipitation testing on a comparatively small scale.

Key findings

Miniaturisation of test equipment is an important trend in pharmaceutics, and several small-scale experiments have been reported for drug dissolution and precipitation testing. Such tests typically employ analytics in real-time. Fibre optic ultraviolet (UV) analytics has become a well-established method in this field. Novel imaging techniques are emerging that use visible or UV light; also promising is Fourier transform infrared imaging based on attenuated total reflection. More information than just a rate constant is obtained from these methods. The early phase of a dissolution process can be assessed and drug precipitation may eventually be observed. Some real-time techniques are particularly well suited to studying drug precipitation during formulation dispersion; for example, turbidity, focused beam reflectance measurement and Raman spectroscopy.

Summary

Small-scale dissolution tests equipped with real-time analytics have become important to screen drug candidates as well as to study prototype formulations in early development. Future approaches are likely to combine different analytical techniques including imaging. Miniaturisation started with mini-vessels or small vials and future assays of dissolution research will probably more often reach the level of parallel well plates and microfluidic channels.

Using ion-selective electrodes to study the drug release from porous cellulose matrices

Polyvinyl chloride (PVC)-based solid-contact ion-selective electrodes (SC-ISEs), responding to propranolol hydrochloride (Pr+) and lidocaine hydrochloride (Ld+) cations as the model drugs with potassium tetrakis(4-chlorophenyl) borate (KTpClPB) as the ion exchanger, were studied. Different drug-polymer solutions were prepared with the model drugs, using different blend ratios of ethylcellulose (EC) and hydroxypropyl cellulose (HPC). Two different solid dosage forms were used. Polymer films were produced by solvent casting method and drug containing porous cellulose samples were prepared by depositing the drug-polymer solutions onto filter paper substrates. The quality of the electrodes and the release profile of Pr+ and Ld+ were investigated with the potentiometric method. The results were compared to UV spectrophotometry. The electrodes were found to be sensitive, precise and functional with a Nernstian behavior over the range of 1.0 × 10-3-3.1 × 10-6 M (9.2 × 10-4-3.0 × 10-1 mg/mL) and 1 × 10-3-2 × 10-6 M (5.4 × 10-4-2.7 × 10-1 mg/mL) at 25 °C for Pr+ and Ld+ sensitive electrodes, respectively. The dynamic response time for the electrodes was less than 10 s. The Pr+ release from porous filter paper was always higher than its equivalent film formulation. Also, lidocaine had higher and faster release from the samples with higher drug concentration. The comparison of the two analytical methods showed near identical results. The ISEs provided a powerful and flexible alternative to UV method in determination of drug release from porous cellulose substrates in a small scale dissolution testing.