The Biopharmaceutics Classification System: subclasses for in vivo predictive dissolution (IPD) methodology and IVIVC

Disposition of two highly permeable drugs in the upper gastrointestinal lumen of healthy adults after a standard high-calorie, high-fat meal

OBJECTIVES

To quantify the presence of two model highly permeable drugs, paracetamol and danazol, in the upper gastrointestinal lumen under conditions simulating the situation after disintegration of immediate release dosage forms administered in bioavailability/bioequivalence studies in the fed state. To understand the drug transfer process from the antral contents through the upper small intestine based on luminal drug data.

METHODS

8 healthy male adult volunteers participated in a randomized, single dose, two-phase, crossover study. After evaluating the impact of homogenization on meal's viscosity and particle size, the meal, containing phenol red as non-absorbable marker, was administered to the antrum via the gastric lumen of a naso-gastro-intestinal tube. The drugs were administered in solution form (Phase I) and in suspension form (Phase II) with a glass of tap water to the antrum of the stomach, 30 min after the initiation of meal administration. Samples were aspirated from the antrum and the upper small intestine up to 4 hours post drug administration.

RESULTS

Apparent concentrations in the aqueous contents of the antrum were higher than apparent concentrations in the micellar contents of the upper small intestine for paracetamol; the opposite was observed for danazol. Based on total drug amount per volume data in contents of the upper gastrointestinal lumen, the transfer of paracetamol (aqueous solution or suspension) and danazol (aqueous suspension) through the upper small intestine could be described as an apparent first-order process. Transfer of a long-chain triglyceride solution of danazol was highly variable.

CONCLUSIONS

Concentrations in the aqueous/micellar phase of luminal contents and values of parameters controlling the transfer from bulk gastric contents through the upper small intestine after a high-calorie, high-fat meal, were reported for the first time for highly permeable drugs. Data are expected to enhance the development of biorelevant in vitro and physiologically based biopharmaceutics modelling methodologies.

Development of a dissolution method for lumefantrine and artemether in immediate release fixed dose artemether/lumefantrine tablets

Background

Dissolution of artemether (ART) and lumefantrine (LUM) active pharmaceutical ingredients (APIs) in fixed dose combination (FDC) ART/LUM tablets is one of the critical quality attributes. Thus, the verification of the release profile of ART and LUM from FDC ART/LUM tablets using a robust and discriminatory dissolution method is crucial. Therefore, the aim of this study was to develop and validate an appropriate dissolution method for quality control of FDC ART/LUM tablets.

Methods

The dissolution medium was selected based on saturation solubility data and sink conditions. The effect of agitation speed, pH and surfactant concentration on the release of ART and LUM was evaluated by employing a two-level factorial experiment. The resulting final method was validated for linearity, precision, robustness and API stability. In addition, the discriminatory power of the method was evaluated using expired and unexpired FDC ART/LUM products.

Results

A suitable dissolution profile of FDC ART/LUM tablets was obtained in 900 ml HCl (0.025 N, pH 1.6) with 1%Myrj 52 using paddle method at 100 rpm and 37 °C. ART and LUM were analysed using a HPLC method with UV detection at wavelengths of 210 and 335 nm, respectively. The results from the stability study showed that ART and LUM were sufficiently stable in HCl (0.025 N, pH 1.6) with 1%Myrj 52 at 37 °C. The method was linear (r² = 0.999) over the concentration range of 6.25–100 μg/ml. The results for precision were within the acceptance limit (%RSD < 2). The percent relative standard deviation (< 2%) and statistically non-significant (p > 0.05) difference in release of ART and LUM observed between deliberately changed dissolution method settings (pH = 1.6 ± 0.2 or agitation speed = 100 ± 2) and optimized dissolution conditions revealed the robustness of the dissolution method. The method was capable to discriminate among different FDC ART/LUM products with different quality.

Conclusions

The developed dissolution method is robust and discriminatory. It can be used in the quality evaluation of FDC ART/LUM tablets.

Hypromellose acetate succinate based amorphous solid dispersions via hot melt extrusion: Effect of drug physicochemical properties

In this study, the impact of drug and hydroxypropyl methylcellulose acetate succinate (HPMCAS) grades physicochemical properties on extrusion process, dissolution and stability of the hot melt extruded amorphous solid dispersions (ASDs) of nifedipine and efavirenz was investigated. Incorporation of drugs affected the extrusion temperature required for solid dispersion preparation. Differential scanning calorimetry and powder X-ray diffraction studies confirmed the amorphous conversion of the drugs in the prepared formulations. The amorphous nature of ASDs was unchanged after 3 months of stability testing at 40 °C and 75% relative humidity. The dissolution efficiency of the ASDs was dependent on the log P of the drug. The inhibitory effect of HPMCAS on drug precipitation was dependent on the hydrophobic interactions between drug and polymer, polymer grade, and dose of the drug. The dissolution efficiency and dissolution rate of the ASDs were dependent on the log P of the drug and solubility and hydrophilicity of the polymer grade respectively. The inhibitory effect of HPMCAS on drug precipitation was dependent on the hydrophobic interactions between drug and polymer, polymer grade, and the dissolution dose of the drug.

Segmental-Dependent Solubility and Permeability as Key Factors Guiding Controlled Release Drug Product Development

The main factors influencing the absorption of orally administered drugs are solubility and permeability, which are location-dependent and may vary along the gastrointestinal tract (GIT). The purpose of this work was to investigate segmental-dependent intestinal absorption and its role in controlled-release (CR) drug product development. The solubility/dissolution and permeability of carvedilol (vs. metoprolol) were thoroughly studied, in vitro/in vivo (Octanol-buffer distribution coefficients (Log D), parallel artificial membrane permeability assay (PAMPA), rat intestinal perfusion), focusing on location-dependent effects. Carvedilol exhibits changing solubility in different conditions throughout the GIT, attributable to its zwitterionic nature. A biorelevant pH-dilution dissolution study for carvedilol immediate release (IR) vs. CR scenario elucidates that while the IR dose (25 mg) may dissolve in the GIT luminal conditions, higher doses used in CR products would precipitate if administered at once, highlighting the advantage of CR from the solubility/dissolution point of view. Likewise, segmental-dependent permeability was evident, with higher permeability of carvedilol vs. the low/high Peff marker metoprolol throughout the GIT, confirming it as a biopharmaceutical classification system (BCS) class II drug. Theoretical analysis of relevant physicochemical properties confirmed these results as well. A CR product may shift the carvedilol's solubility behavior from class II to I since only a small dose portion needs to be solubilized at a given time point. The permeability of carvedilol surpasses the threshold of metoprolol jejunal permeability throughout the entire GIT, including the colon, establishing it as a suitable candidate for CR product development. Altogether, this work may serve as an analysis model in the decision process of CR formulation development and may increase our biopharmaceutical understanding of a successful CR drug product.

Exploring the impact of real-life dosing conditions on intraluminal and systemic concentrations of atazanavir in parallel with gastric motility recording in healthy subjects

This work strived to explore gastrointestinal (GI) dissolution, supersaturation and precipitation of the weakly basic drug atazanavir in humans under different 'real-life' intake conditions. The impact of GI pH and motility on these processes was thoroughly explored. In a cross-over study, atazanavir (Reyataz®) was orally administered to 5 healthy subjects with (i) a glass of water, (ii) a glass of Coca-Cola® and (iii) a glass of water under hypochlorhydric conditions (induced by concomitant intake of a proton-pump inhibitor (PPI)). After intake, GI fluids were aspirated from the stomach and the duodenum and, subsequently, analyzed for atazanavir. In parallel, blood samples were collected to assess systemic concentrations. In general, the results of this study revealed that the acidic gastric pH in combination with gastric residence time played a crucial role in the dissolution of atazanavir along the GI tract. After intake of atazanavir with a glass of water (i.e., reference condition), complete gastric dissolution was observed. After GI transfer, supersaturation was noticed for a limited amount of time (1.25 h). With respect to the Coca-Cola® condition, complete gastric dissolution was also observed. A delay in gastric emptying, highly likely caused by the caloric content (101 kcal), was responsible for delayed arrival of atazanavir into the upper small intestine, creating a longer time window of supersaturated concentrations in the duodenal segment (3.25 h) compared to the water condition. The longer period of supersaturated concentrations resulted in a slightly higher systemic exposure of atazanavir compared to the condition when atazanavir was taken with a glass of water. A remarkable observation was the creation (when the drug was given in the migrating motor complex (MMC) phase 2) or maintenance (when the drug was given in MMC phase 1) of a quiescent phase for up to 80 min. With respect to the PPI condition, negligible gastric and intestinal concentrations were observed, resulting in minimal systemic exposure for all subjects. It can be concluded that gastric pH and residence time play a pivotal role in the intestinal disposition of atazanavir in order to generate sufficiently high concentrations further down in the intestinal tract for a sufficient period of time, thus creating a beneficial driving force for intestinal absorption.

A multiscale absorption and transit model for oral drug delivery: Formulation and applications during fasting conditions

Most Food and Drug Administration (FDA)-approved drugs are administered orally, despite the complex process of oral drug absorption that is difficult to analyze experimentally. Oral bioavailability is dependent on the drug compound as well as the physiological and anatomical states of the user. Thus, computational models have emerged to mechanistically capture and predict the oral absorption process. The current models are generally 0D compartmental models and are limited by (a) simplified physiological characteristics of the gastrointestinal tract (GIT), (b) semiempirical/analytical dissolution profiles of the tested drugs, (c) incorrect absorption for some drug BCS classes (class IIa, for example), (d) GITs size variability among population, (e) incorrectly predicting the absorption of drugs that are GIT target specific, and (f) erroneous mixing in the domain. In this study, we have developed a multiscale absorption and transit (MAT) toolkit to simulate the dissolution, transport, absorption, distribution, metabolism, and elimination of orally administered drugs in the human GIT at multiple levels. MAT was constructed by integrating the spatially accurate first-principles driven high-fidelity drug transport, dissolution, and absorption model in the human stomach and GIT using our recently published quasi-3D (Q3D) framework. The process integrated the multilayer intestine physiologically based pharmacokinetics models with the whole-body compartmental models to predict the systemic pharmacokinetics of oral drugs. The computational results showed that this multiscale tool was able to match the experimental concentration results (individual and population) better than the traditional compartmental models. Ultimately, MAT will be developed into a commercial product to meet urgent demands from pharmaceutical and biomedical industries.

Formulation and evaluation of cyclodextrin-based nanosponges of griseofulvin as pediatric oral liquid dosage form for enhancing bioavailability and masking bitter taste

The aim of this study was the development of griseofulvin (GRI) loaded β-cyclodextrin (β–CD) based nanosponges for bitter taste masking, improving dissolution rate and oral bioavailability. Plain NS (NS1 NS2 and NS3) were fabricated by reacting β-CD with the cross-linker diphenyl carbonate at different molar ratios (1:2, 1:4 and 1:6, respectively) using ultrasonication method. The NS2 provided both highest %yield and GRI solubilization enhancement. Thus, the drug was loaded in NS2 at different NS2: drug weight ratios in presence or absence of 0.25%w/w polyvinylpyrolidone (PVP k30). The GRI loaded NS (F1) that provided highest drug loading capacity and entrapment efficiency (47.20 ± 0.38%, 84.91 ± 0.30%, respectively) was morphologically examined using scanning electron microscopy (SEM). Also, Particle size, zeta potential, differential scanning calorimetry (DSC), Fourier transform infra-red (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, in-vitro release, taste masking potential were evaluated. Moreover, in-vivo Pharmacokinetic studies were performed on rats. The F1 showed particle size 665.9 ± 13.8 nm and zeta potential −21.5 ± 0.7 mV. The DSC and FT-IR analysis confirmed the complexation of GRI with NS2. Nanosponges (F1) provided 3.19, folds increase in dissolution efficiency %, 2.13 and 3.78 folds increase in C_max and AUC_0-48 compared to plain GRI. Taste masking evaluation confirmed the potential of GRI nanosponges (F1) in masking the bitter taste of GRI completely. The study confirmed that complexation of GRI with NS would be a viable approach for masking the bitter taste of GRI and improving oral bioavailability, that Cmax, Tmax and AUC 0–48 were significantly higher for the developed formulation (F1).

Selection of In Vivo Predictive Dissolution Media Using Drug Substance and Physiological Properties

The rate and extent of drug dissolution in the gastrointestinal (GI) tract are highly dependent upon drug physicochemical properties and GI fluid properties. Biorelevant dissolution media (BDM), which aim to facilitate in vitro prediction of in vivo dissolution performance, have evolved with our understanding of GI physiology. However, BDM with a variety of properties and compositions are available, making the choice of dissolution medium challenging. In this tutorial, we describe a simple and quantitative methodology for selecting practical, yet physiologically relevant BDM representative of fasted humans for evaluating dissolution of immediate release formulations. Specifically, this methodology describes selection of pH, buffer species, and concentration and evaluates the importance of including bile salts and phospholipids in the BDM based upon drug substance log D, pK_a, and intrinsic solubility. The methodology is based upon a mechanistic understanding of how three main factors affect dissolution, including (1) drug ionization at gastrointestinal pH, (2) alteration of surface pH by charged drug species, and (3) drug solubilization in mixed lipidic aggregates comprising bile salts and phospholipids. Assessment of this methodology through testing and comparison with literature reports showed that the recommendations correctly identified when a biorelevant buffer capacity or the addition of bile salts and phospholipids to the medium would appreciably change the drug dissolution profile. This methodology can enable informed decisions about when a time, complexity, and/or cost-saving buffer is expected to lead to physiologically meaningful in vitro dissolution testing, versus when a more complex buffer would be required.

Evaluating supersaturation in vitro and predicting its performance in vivo with Biphasic gastrointestinal Simulator: A case study of a BCS IIB drug

This study aimed to develop an evaluation approach for supersaturation by employing an in vitro bio-mimicking apparatus designed to predict in vivo performance. The Biphasic Gastrointestinal Simulator (BGIS) is composed of three chambers with absorption phases that represent the stomach, duodenum, and jejunum, respectively. The concentration of apatinib in each chamber was detected by fiber optical probes in situ. The dissolution data and the pharmacokinetic data were correlated by Gastroplus^TM. The precipitates were characterized by polarizing microscope, Scanning Electron Microscopy, Powder X-ray diffraction and Differential scanning calorimetry. According to the results, Vinylpyrrolidone-vinyl acetate copolymer (CoPVP) prolonged supersaturation by improving solubility and inhibiting crystallization, while Hydroxypropyl methylcellulose (HPMC) prolonged supersaturation by inhibiting crystallization alone. Furthermore, a predictive in vitro-in vivo correlation was established, which confirmed the anti-precipitation effect of CoPVP and HPMC on in vitro performance and in vivo behavior. In conclusion, CoPVP and HPMC increased and prolonged the supersaturation of apatinib, and then improved its bioavailability. Moreover, BGIS was demonstrated to be a significant approach for simulating in vivo conditions for in vitro-in vivo correlation in a supersaturation study. This study presents a promising approach for evaluating supersaturation, screening precipitation inhibitors in vitro, and predicting their performances in vivo.

Engineering of Naproxen Loaded Polymer Hybrid Enteric Microspheres for Modified Release Tablets: Development, Characterization, in silico Modelling and in vivo Evaluation

BACKGROUND

Naproxen (NP) is a non-steroidal anti-inflammatory drug with poor aqueous solubility and low oral bioavailability, which may lead to therapeutic failure. NP causes crucial GIT irritation, bleeding, and peptic and duodenal ulcers.

PURPOSE OF THE STUDY

This study aimed to engineer and characterize polymer hybrid enteric microspheres using an integrated (experimental and molecular modelling) approach with further development to solid dosage form with modified drug release kinetics and improved bioavailability.

MATERIALS AND METHODS

NP loaded polymer hybrid enteric microspheres (PHE-Ms) were fabricated by using a modified solvent evaporation technique coupled with molecular modelling (MM) approach. The PHE-Ms were characterized by particle size, distribution, morphology, crystallinity, EE, drug-polymer compatibility, and DSC. The optimized NP loaded PHE-Ms were further subjected to downstream procedures including tablet dosage form development, stability studies and comparative in vitro-in vivo evaluation.

RESULTS

The hydrophobic polymer EUD-L100 and hydrophilic polymer HPMC-E5 delayed and modified drug release at intestinal pH while imparting retardation of NP release at gastric pH to diminish the gastric side effects. The crystallinity of the NP loaded PHE-Ms was established through DSC and P (XRD). The particle size for the developed formulations of PEH-Ms (M1-M5) was in the range from 29.06 ±7.3-74.31 ± 17.7 μm with Span index values of 0.491-0.69, respectively. The produced NP hybrid microspheres demonstrated retarded drug release at pH 1.2 and improved dissolution at pH 6.8. The in vitro drug release patterns were fitted to various release kinetic models and the best-followed model was the Higuchi model with a release exponent "n" value > 0.5. Stability studies at different storage conditions confirmed stability of the NP loaded PHE-Ms based tablets (P<0.05). The molecular modelling (MM) study resulted in adequate binding energy of co-polymer complex SLS-Eudragit-HPMC-Naproxen (-3.9 kcal/mol). In contrast to the NP (unprocessed) and marketed formulations, a significant increase in the Cmax of PHE-MT1 (44.41±4.43) was observed.

CONCLUSION

The current study concludes that developing NP loaded PHE-Ms based tablets could effectively reduce GIT consequences with restored therapeutic effects. The modified release pattern could improve the dissolution rate and enhancement of oral bioavailability. The MM study strengthens the polymer-drug relationship in microspheres.

In Vitro Dissolution and in Silico Modeling Shortcuts in Bioequivalence Testing

Purpose: To review in vitro testing and simulation platforms that are in current use to predict in vivo performances of generic products as well as other situations to provide evidence for biowaiver and support drug formulations development. Methods: Pubmed and Google Scholar databases were used to review published literature over the past 10 years. The terms used were “simulation AND bioequivalence” and “modeling AND bioequivalence” in the title field of databases, followed by screening, and then reviewing. Results: A total of 22 research papers were reviewed. Computer simulation using software such as GastroPlus™, PK-Sim^® and SimCyp^® find applications in drug modeling. Considering the wide use of optimization for in silico predictions to fit observed data, a careful review of publications is required to validate the reliability of these platforms. For immediate release (IR) drug products belonging to the Biopharmaceutics Classification System (BCS) classes I and III, difference factor (ƒ₁) and similarity factor (ƒ₂) are calculated from the in vitro dissolution data of drug formulations to support biowaiver; however, this method can be more discriminatory and may not be useful for all dissolution profiles. Conclusions: Computer simulation platforms need to improve their mechanistic physiologically based pharmacokinetic (PBPK) modeling, and if prospectively validated within a small percentage of error from the observed clinical data, they can be valuable tools in bioequivalence (BE) testing and formulation development.

Ionic Liquid Forms of the Antimalarial Lumefantrine in Combination with LFCS Type IIIB Lipid-Based Formulations Preferentially Increase Lipid Solubility, In Vitro Solubilization Behavior and In Vivo Exposure

Lipid based formulations (LBFs) are commonly employed to enhance the absorption of highly lipophilic, poorly water-soluble drugs. However, the utility of LBFs can be limited by low drug solubility in the formulation. Isolation of ionizable drugs as low melting, lipophilic salts or ionic liquids (ILs) provides one means to enhance drug solubility in LBFs. However, whether different ILs benefit from formulation in different LBFs is largely unknown. In the current studies, lumefantrine was isolated as a number of different lipophilic salt/ionic liquid forms and performance was assessed after formulation in a range of LBFs. The solubility of lumefantrine in LBF was enhanced 2- to 80-fold by isolation as the lumefantrine docusate IL when compared to lumefantrine free base. The increase in drug loading subsequently enhanced concentrations in the aqueous phase of model intestinal fluids during in vitro dispersion and digestion testing of the LBF. To assess in vivo performance, the systemic exposure of lumefantrine docusate after administration in Type II-MCF, IIIB-MCF, IIIB-LCF, and IV formulations was evaluated after oral administration to rats. In vivo exposure was compared to control lipid and aqueous suspension formulations of lumefantrine free base. Lumefantrine docusate in the Type IIIB-LCF showed significantly higher plasma exposure compared to all other formulations (up to 35-fold higher). The data suggest that isolation of a lipid-soluble IL, coupled with an appropriate formulation, is a viable means to increase drug dose in an oral formulation and to enhance exposure of lumefantrine in vivo.

Physiological parameters of the gastrointestinal fluid impact the dissolution behavior of the BCS class IIa drug valsartan

The objective of this study was to investigate the effect of the physiological parameters (pH, buffer capacity, and ionic strength) of the gastrointestinal (GI) fluid on the dissolution behavior of the class II weakly acidic (BCS class IIa) drug valsartan. A series of in vitro dissolution studies was carried out on Diovan^® immediate release tablets using media that cover the physiological range of pH (1.2-7.8), buffer capacity (0-0.047 M/ΔpH), and ionic strength (0-0.4 mol/L) of the GI fluid during fasted and fed states using the conventional USP II apparatus. Valsartan exhibited pH- and buffer capacity-dependent dissolution behavior, where valsartan release was slow and incomplete in media simulating gastric fluid with low pH, and fast and complete in media simulating intestinal fluid with high pH. In addition, the rate of valsartan release increased with increasing the buffer capacity of the dissolution medium. In water and NaCl solutions, valsartan release was incomplete and the dissolution profiles were similar regardless of the ionic strength of the medium, indicating an ionic strength-independent dissolution behavior. These results highlight the significant effect of the physiological parameters of the GI fluid on the dissolution behavior of BCS class IIa drugs.

In silico Tools at Early Stage of Pharmaceutical Development: Data Needs and Software Capabilities

In early drug development, the selection of a formulation platform and decisions on formulation strategies have to be made within a short timeframe and often with minimal use of the active pharmaceutical ingredient (API). The current work evaluated the various physicochemical parameters required to improve the prediction accuracy of simulation software for immediate release tablets in early drug development. DDDPlus™ was used in simulating dissolution test profiles of immediate release tablets of ritonavir and all simulations were compared with experimental results. The minimum data requirements to make useful predictions were assessed using the ADMET predictor (part of DDDPlus) and Chemicalize (an online resource). A surfactant model was developed to estimate the solubility enhancement in media containing surfactant and the software's transfer model based on the USP two-tiered dissolution test was assessed. One measured data point was shown to be sufficient to make predictive simulations in DDDPlus. At pH 2.0, the software overestimated drug release while at pH 1.0 and 6.8, simulations were close to the measured values. A surfactant solubility model established with measured data gave good dissolution predictions. The transfer model uses a single-vessel model and was unable to predict the two in vivo environments separately. For weak bases like ritonavir, a minimum of three solubility data points is recommended for in silico predictions in buffered media. A surfactant solubility model is useful when predicting dissolution behavior in surfactant media and in silico predictions need measured solubility data to be predictive.

Simulated, biorelevant, clinically relevant or physiologically relevant dissolution media: The hidden role of bicarbonate buffer

In-vitro dissolution testing of pharmaceutical formulations has been used as a quality control test for many years. At early drug product development, in vivo predictive dissolution testing can be used for guidance in the rational selection of candidate formulations that best fit the desired in vivo dissolution characteristics. At present, the most widely applied dissolution media are phosphate-based buffers and, in some cases, the result of dissolution tests performed in such media have demonstrated reasonable/acceptable IVIVCs. However, the presence of phosphates in human GI luminal fluids is insignificant, which makes the use of such media poorly representative of the in vivo environment. The gastrointestinal lumen has long been shown to be buffered by bicarbonate. Hence, much interest in the development of suitable biorelevant in vitro dissolution media based on bicarbonate buffer systems has evolved. However, there are inherent difficulties associated with these buffers, such as maintaining the pH throughout the dissolution test, as CO₂ tends to leave the system. Various mathematical models have been proposed to analyze bicarbonate buffers and they are discussed in this review. Approaches such as using simpler buffer systems instead of bicarbonate have been proposed as surrogate buffers to produce an equivalent buffer effect on drug dissolution on a case-by-case basis. There are many drawbacks related to simpler buffers systems including their poor in vivo predictability. Considerable discrepancies between phosphate and bicarbonate buffer dissolution results have been reported for certain dosage forms, e.g. enteric coated formulations. The role and need of bicarbonate-based buffers in quality control testing requires scientific analysis. This review also encompasses on the use of bicarbonate-based buffers as a potentially in vivo predictive dissolution medium for enteric coated dosage forms.

"Development of Fixed Dose Combination Products" Workshop Report: Considerations of Gastrointestinal Physiology and Overall Development Strategy

The gastrointestinal (GI) tract is one of the most popular and used routes of drug product administration due to the convenience for better patient compliance and reduced costs to the patient compared to other routes. However, its complex nature poses a great challenge for formulation scientists when developing more complex dosage forms such as those combining two or more drugs. Fixed dose combination (FDC) products are two or more single active ingredients combined in a single dosage form. This formulation strategy represents a novel formulation which is as safe and effective compared to every mono-product separately. A complex drug product, to be dosed through a complex route, requires judicious considerations for formulation development. Additionally, it represents a challenge from a regulatory perspective at the time of demonstrating bioequivalence (BE) for generic versions of such drug products. This report gives the reader a summary of a 2-day short course that took place on the third and fourth of November at the Annual Association of Pharmaceutical Scientists (AAPS) meeting in 2018 at Washington, D.C. This manuscript will offer a comprehensive view of the most influential aspects of the GI physiology on the absorption of drugs and current techniques to help understand the fate of orally ingested drug products in the complex environment represented by the GI tract. Through case studies on FDC product development and regulatory issues, this manuscript will provide a great opportunity for readers to explore avenues for successfully developing FDC products and their generic versions.

Application of the QbD-based approach in the early development of liposomes for nasal administration

In this study, authors adapt the Quality by Design (QbD) concept as well as the Risk Assessment (RA) method to the early development phase of a new nano-sized liposomal formulation for nasal administration with brain target. As a model active agent, a BCS II class drug was chosen to investigate the behaviour of the drugs with lipophilic character. This research presents how to apply this risk-focused approach and concentrates on the first four stages of the QbD implementation. In this way the quality target product profile was defined, the critical factors were identified and an RA was performed. The RA results helped in the factorial design-based liposome preparation by the lipid film hydration method. The prepared liposomes were evaluated (vesicle size, size distribution, and specific surface area). The surface characteristics were also investigated to verify the exactness of the RA and critical factors based theoretical prediction. The results confirm that the QbD approach in liposome development can improve the formulation process. The RA focused predictive approach resulted in a decreased number of studies in practice but in an effective product preparation. Using such innovative design and development models can help to optimise and rationalise the development of liposomes.

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.

Modifying release of poorly soluble active pharmaceutical ingredients with the amine functionalized SBA-16 type mesoporous materials

SBA-16 and two modified SBA-16 type ordered mesoporous silica were used as the carriers for ibuprofen (anti-inflammatory drug) and furosemide (loop diuretic drug). Modification of the solid carrier was prepared with chitosan or N-3[(amino(poly-propylenoxy)]aminopropyltrimethoxysilane. The samples of carriers and carrier-drug loaded materials were characterized by X-ray diffraction, N₂ adsorption, Fourier-transform infrared spectroscopy, thermogravimetry, and differential scanning calorimetry. The release profiles of active pharmaceutical ingredients were performed in media with different pH in the USP 2 apparatus as well as in two biorelevant media (fasted state simulated gastric fluid and fasted state small intestinal fluid) in USP 4 apparatus. The loading of active substances into mesoporous materials was performed with modified immersion method. The maximum content of deposited drug in mesoporous material was close to 12.0 and 2.2 wt.% for ibuprofen and furosemide, respectively. After drug adsorption, the reduction of BET surface area, pore volume and pore diameter of non-modified and modified SBA-16 was observed, while the cubic arrays of siliceous matrix were well preserved. The release profiles of ibuprofen and furosemide loaded in mesoporous materials in media with different pH and biorelevant fasted state simulated gastric fluid and fasted state small intestinal fluid showed that the new SBA-16 type materials modify the release profiles of furosemide, increasing the dissolution rate of these substances in the medium at pH 1.2. The cytotoxicity of the materials and permeability of drugs after their loading on SBA-16 materials were evaluated on Caco-2 model. The results of our study showed that mesoporous materials did not exert cytotoxic effects and did not influence on the permeability of both active pharmaceutical ingredients in relation to pure substances.

A novel technique for intraduodenal administration of drug suspensions/solutions with concurrent pH monitoring applied to ibuprofen formulations

Characterization of dissolution of solid suspended drug particles in vivo is important for developing biopredictive in vitro tests. Therefore, methods to gain deeper insights into particle dissolution in vivo are needed. The soft Bioperm intubation method, a well established tool for investigation of permeability, absorption, metabolism, and drug interactions at predefined locations in the gastroinstinal tract, was modified. The novel intubation method involved pump-controlled infusion of pharmaceutical suspensions as well as simultaneous pH monitoring. This technique was used in a proof of concept study in healthy humans. Plasma sampling and non-compartmental analysis allowed comparison of three different ibuprofen drug products, a solution and two suspensions with different particle size distribution, as well as two different infusion rates. Both a particle size effect and an effect of altering infusion rates on pharmacokinetic parameters were shown. Moreover, it was possible to monitor intestinal pH changes after intestinal infusion. Infusion of ibuprofen resulted in a pH drop that was quantified by the concept of Area Between Curves (ABC).

Application of data mining approach to identify drug subclasses based on solubility and permeability

Solubility and permeability are recognized as key parameters governing drug intestinal absorption and represent the basis for biopharmaceutics drug classification. The Biopharmaceutics Classification System (BCS) is widely accepted and adopted by regulatory agencies. However, currently established low/high permeability and solubility boundaries are the subject of the ongoing scientific discussion. The aim of the present study was to apply data mining analysis on the selected drugs data set in order to develop a human permeability predictive model based on selected molecular descriptors, and to perform data clustering and classification to identify drug subclasses with respect to dose/solubility ratio (D/S) and effective permeability (P_eff ). The P_eff values predicted for 30 model drugs for which experimental human permeability data are not available were in good agreement with the reported fraction of drug absorbed. The results of clustering and classification analysis indicate the predominant influence of P_eff over D/S. Two P_eff cut-off values (1 × 10^-4 and 2.7 × 10^-4  cm/s) have been identified indicating the existence of an intermediate group of drugs with moderate permeability. Advanced computational analysis employed in the present study enabled the recognition of complex relationships and patterns within physicochemical and biopharmaceutical properties associated with drug bioperformance.

Prediction of the Oral Pharmacokinetics and Food Effects of Gabapentin Enacarbil Extended-Release Tablets Using Biorelevant Dissolution Tests

The purpose of this research was to establish an in vitro dissolution testing method to predict the oral pharmacokinetic (PK) profiles and food effects of gabapentin enacarbil formulated as wax matrix extended-release (ER) tablets in humans. We adopted various biorelevant dissolution methods using the United States Pharmacopeia (USP) apparatus 2, 3 and 4 under simulated fasted and fed states. Simulated PK profiles using the convolution approach were compared to published in vivo human PK data. USP apparatus 2 and 4 underestimated the in vivo performance due to slow in vitro dissolution behaviors. In contrast, biorelevant dissolution using USP apparatus 3 coupled with the convolution approach successfully predicted the oral PK profile of gabapentin enacarbil after oral administration of a Regnite^® tablet under fasted state. This approach might be useful for predicting the oral PK profiles of other drugs formulated as wax matrix-type ER tablets under fasted state.

Systematic synthesis of a 6-component organic-salt alloy of naftopidil, and pentanary, quaternary and ternary multicomponent crystals

The single-crystal X-ray structure of a 6-component organic-salt alloy (hexanary) of naftopidil (1) (an active pharmaceutical ingredient) with benzoic acid (2) and four different hydroxy-substituted benzoic acids, i.e. salicylic acid (3), 2,3-di-hydroxybenzoic acid (4), 2,4-di-hydroxybenzoic acid (5) and 2,6-di-hydroxybenzoic acid (6), is reported. The hexanary assembly originates from the observation that the binary salts of naftopidil with the above acids are isostructural. In addition to the 6-component solid, we also describe five 5-component, ten 4-component, and ten 3-component organic-salt alloys of naftopidil (1) with carboxylic acids (2)-(6). These alloys were obtained from different combinations of the acids with the drug. The synthetic design of the multicomponent organic alloys is based on the rationale of geometrical factors (shape and size) and chemical interactions (hydrogen bonds). The common supramolecular synthon in all these crystal structures was the cyclic N+-H⋯O- and O-H⋯O hydrogen-bonded motif of (9) graph set between the 2-hy-droxyammonium group of naftopidil and the carboxyl-ate anion. This ionic synthon is strong and robust, directing the isostructural assembly of naftopidil with up to five different carboxylic acids in the crystal structure together with the lower-level multicomponent adducts. Solution crystallization by slow evaporation provided the multicomponent organic salts and alloys which were characterized by a combination of single-crystal X-ray diffraction, powder X-ray diffraction, NMR and differential scanning calorimetry techniques.

Using pH Gradient Dissolution with In-Situ Flux Measurement to Evaluate Bioavailability and DDI for Formulated Poorly Soluble Drug Products

This study described a pH-gradient dissolution method combined with flux measurements as an in vitro tool for assessing the risk of bioavailability reduction due to drug-drug interactions (DDI) caused by acid reducing agents (ARAs). The device incorporates absorption chambers into USP II dissolution vessels, with fiber optic UV-probes monitoring concentration in situ. Dosage forms of Genentech BCS class II drugs, GDC-0810, GDC-0941, and compound A, were tested by starting the dissolution in either pH 1.6 or pH 4.0 media then converting to FaSSIF after 30 min. GDC-0810 showed no significant difference in flux between the two conversion experiments. A supersaturation phase was observed for GDC-0941 in the pH 1.6 experiments after media conversion to FaSSIF; however, it did not appear to occur in the pH 4.0 experiment due to low drug solubility at pH 4.0, resulting in a 95% decrease in flux compared to pH 1.6 experiment. The extent of flux reduction and the total accumulated API mass in the absorption chamber agreed well with the 89% reduction in mean Cmax and the 82% reduction in mean AUC from dog PK study between animals treated with pentagastrin and famotidine. Testing of the compound A optimized formulation tablets showed a 25% reduction in flux and in vitro absorbed amount by changing pH 1.6 to 4.0, correlating well with the AUC decrease in clinical studies. Good correlation between in vitro data and in vivo PK data demonstrated the applicability of the method for formulators to develop drug products mitigating DDI from ARAs.

Physical properties and solubility studies of Nifedipine-PEG 1450/HPMCAS-HF solid dispersions

Low-order high-energy nifedipine (NIF) solid dispersions (SDs) were generated by melt solvent amorphization with polyethylene glycol (PEG) 1450 and hypromellose acetate succinate (HPMCAS-HF) to increase NIF solubility while achieving acceptable physical stability. HPMCAS-HF was used as a crystallization inhibitor. Individual formulation components, their physical mixtures (PMs), and SDs were characterized by differential scanning calorimetry, powder X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR). NIF solubility and percent crystallinity (PC) were determined at the initial time and after 5 days stored at 25 °C and 60% RH. FTIR indicated that hydrogen bonding was involved with the amorphization process. FTIR showed that NIF:HPMCAS-HF intermolecular interactions were weaker than NIF:PEG 1450 interactions. NIF:PEG 1450 SD solubilities were significantly higher than their PM counterparts (p < 0.0001). The solubilities of NIF:PEG 1450:HPMCAS-HF SDs were significantly higher than their corresponding NIF:PEG 1450 SDs (p < 0.0001-0.043). All the SD solubilities showed a statistically significant decrease (p < 0.0001) after storage for 5 days. SDs PC were statistically lower than their comparable PMs (p < 0.0001). The PCs of SDs with HPMCAS-HF were significantly lower than SDs not containing only PEG 1450. All SDs exhibited a significant increase in PC (p < 0.0001-0.0089) on storage. Thermogravimetric analysis results showed that HPMCAS-HF bound water at higher temperatures than PEG 1450 (p < 0.0001-0.0039). HPMCAS-HF slowed the crystallization process of SDs, although it did not completely inhibit NIF crystal growth.

Overview of Transporters in Pharmacokinetics and Drug Discovery

Transporters play important roles in absorption, distribution, metabolism, and elimination (ADME) processes, as well as drug pharmacokinetics (PK) and pharmacodynamics (PD). They are also important in maintaining the homeostasis of endogenous compounds and nutrients in the body. Increasing evidences also suggest that they are important in mediating drug-drug interactions (DDIs). While the significance of transporters in drug pharmacodynamics and DDIs are beyond the scope of this overview, the basic concepts of transporters, their contributions in membrane permeation processes, and their roles in influencing drug ADME pathway and PK will be discussed. © 2018 by John Wiley & Sons, Inc.

Evaluation and optimized selection of supersaturating drug delivery systems of posaconazole (BCS class 2b) in the gastrointestinal simulator (GIS): An in vitro-in silico-in vivo approach

Supersaturating drug delivery systems (SDDS) have been put forward in the recent decades in order to circumvent the issue of low aqueous solubility. Prior to the start of clinical trials, these enabling formulations should be adequately explored in in vitro/in silico studies in order to understand their in vivo performance and to select the most appropriate and effective formulation in terms of oral bioavailability and therapeutic outcome. The purpose of this work was to evaluate the in vivo performance of four different oral formulations of posaconazole (categorized as a biopharmaceutics classification system (BCS) class 2b compound) based on the in vitro concentrations in the gastrointestinal simulator (GIS), coupled with an in silico pharmacokinetic model to predict their systemic profiles. Recently published intraluminal and systemic concentrations of posaconazole for these formulations served as a reference to validate the in vitro and in silico results. Additionally, the morphology of the formed precipitate of posaconazole was visualized and characterized by optical microscopy studies and thermal analysis. This multidisciplinary work demonstrates an in vitro-in silico-in vivo approach that provides a scientific basis for screening SDDS by a user-friendly formulation predictive dissolution (fPD) device in order to rank these formulations towards their in vivo performance.