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

The development of a novel simultaneous in vitro dissolution - in situ perfusion system as a potential tool for studying the absorption of solid oral formulation in rat

The aim of this work is to develop a novel simultaneous in vitro dissolution - in situ perfusion system (SDPS) as a potential tool to evaluate the in vivo performance of solid oral formulation in rat. The innovative nitrendipine (NTD) tablet of Bayotensin mite® made in Germany was used as reference listed drug (RLD), and five generic products from Chinese market were compared with RLD using the in vitro dissolution test method specified by the orange book and the SDPS method developed in this study. Four self-prepared NTD tablets with different proportions of microcrystalline cellulose/starch were employed to investigate the discriminatory ability of the SDPS for formulation. In addition, the predictivity of the SDPS in relation to data from in vivo pharmaceutics studies was evaluated. The 45-min dissolution test and multiple-pH dissolution profiles of generic product 1 and 2 have no difference compared with the RLD, but their dissolution profiles from the SDPS showed statistically significant differences. A biexponential formula successfully described the concentration profiles of self-prepared formulations in SDPS experiments. The kdis (0.08 ± 0.01 ∼ 0.2 ± 0.03 min-1) and ka (about 2.30 × 10-3 min-1) values calculated by the formulas of F1-F3 suggested that the used excipients had no effect on the intestinal absorption of NTD, and it might be the property of active pharmaceutical ingredient that led to the difference among the generics. Furthermore, the in vivo rat pharmacokinetics study results of F1-F3 showed a good correlation (R2 = 0.99) with the SDPS data. In summary, the SDPS is a promising tool to detect the unexpected quality changes of pharmaceutical products in weakly regulated markets, facilitate formulation screening, and potentially reduce animal testing for estimating the in vivo absorption behavior of solid oral formulations. The absorption performance of generic drugs in vivo should be further investigated.

Revisiting Supersaturation of a Biopharmaceutical Classification System IIB Drug: Evaluation via a Multi-Cup Dissolution Approach and Molecular Dynamic Simulation

As a subclass of the biopharmaceutical classification system (BCS) class II, basic drugs (BCS IIB) exhibit pH-dependent solubility and tend to generate supersaturation in the gastrointestinal tract, leading to less qualified in vitro-in vivo correlation (IVIVC). This study aims to develop a physiologically based multi-cup dissolution approach to improve the evaluation of the supersaturation for a higher quality of IVIVC and preliminarily explores the molecular mechanism of supersaturation and precipitation of ketoconazole affected by Polyvinylpyrrolidone-vinyl acetate copolymer (PVPVA) and hydroxypropyl methyl-cellulose (HPMC). The concentration of ketoconazole in each cup of the dynamic gastrointestinal model (DGIM) was measured using fiber optical probes. Molecular interactions between ketoconazole and PVPVA or HPMC were simulated by Materials Studio. The results demonstrated that PVPVA and HPMC improved and maintained the supersaturation of ketoconazole. PVPVA exhibited superior precipitation inhibitory effect on ketoconazole molecule aggregation due to slightly stronger van der Waals forces as well as unique electrostatic forces, thereby further enhancing in vitro drug absorption, which correlated well with in vivo drug absorption. Compared with a conventional dissolution apparatus paddle method, the DGIM improved the mean prediction error through the IVIVC from 19.30% to 9.96%, reaching the qualification criteria. In conclusion, the physiologically based multi-cup dissolution approach enables improved evaluation of supersaturation in gastrointestinal transportation of BCS IIB drug ketoconazole, enabling screening screen precipitation inhibitors and achieving qualified IVIVC for drug formulation studies.

Supersaturation and Precipitation Applicated in Drug Delivery Systems: Development Strategies and Evaluation Approaches

Supersaturation is a promising strategy to improve gastrointestinal absorption of poorly water-soluble drugs. Supersaturation is a metastable state and therefore dissolved drugs often quickly precipitate again. Precipitation inhibitors can prolong the metastable state. Supersaturating drug delivery systems (SDDS) are commonly formulated with precipitation inhibitors, hence the supersaturation is effectively prolonged for absorption, leading to improved bioavailability. This review summarizes the theory of and systemic insight into supersaturation, with the emphasis on biopharmaceutical aspects. Supersaturation research has developed from the generation of supersaturation (pH-shift, prodrug and SDDS) and the inhibition of precipitation (the mechanism of precipitation, the character of precipitation inhibitors and screening precipitation inhibitors). Then, the evaluation approaches to SDDS are discussed, including in vitro, in vivo and in silico studies and in vitro-in vivo correlations. In vitro aspects involve biorelevant medium, biomimetic apparatus and characterization instruments; in vivo aspects involve oral absorption, intestinal perfusion and intestinal content aspiration and in silico aspects involve molecular dynamics simulation and pharmacokinetic simulation. More physiological data of in vitro studies should be taken into account to simulate the in vivo environment. The supersaturation theory should be further completed, especially with regard to physiological conditions.

Supersaturation and phase behavior during dissolution of amorphous solid dispersions

Amorphous solid dispersion (ASD) is a promising strategy to enhance solubility and bioavailability of poorly water-soluble drugs. Due to higher free energy of ASD, supersaturated drug solution could be generated during dissolution. When amorphous solubility of a drug is exceeded, drug-rich nanodroplets could form and act as a reservoir to maintain the maximum free drug concentration in solution, facilitating the absorption of the drug in vivo. Dissolution behavior of ASD has received increasing interests. This review will focus on the recent advances in ASD dissolution, including the generation and maintenance of supersaturated drug solution in absence or presence of liquid-liquid phase separation. Mechanism of drug release from ASD including polymer-controlled dissolution and drug-controlled dissolution will be introduced. Formation of amorphous drug-rich nanodroplets during dissolution and the underlying mechanism will be discussed. Phase separation morphology of hydrated ASD plays a critical role in dissolution behavior of ASD, which will be highlighted. Supersaturated drug solution shows poor physical stability and tends to crystallize. The effect of polymer and surfactant on supersaturated drug solution will be demonstrated and some unexpected results will be shown. Physicochemical properties of drug and polymer could impact ASD dissolution and some of them even show opposite effect on dissolution and physical stability of ASD in solid state, respectively. This review will contribute to a better understanding of ASD dissolution and facilitate a rational design of ASD formulation.

Supercritical fluid chromatography tandem mass spectrometry employed with evaporation-free liquid-liquid extraction for the rapid analysis of cinnarizine in rat plasma

Cinnarizine is a weak base, which can produce supersaturation and precipitation during gastrointestinal transit, affecting its absorption in vivo. Therefore, it is necessary to investigate whether the oral bioavailability of cinnarizine can be improved after co-administration with precipitation inhibitors or not. In order to evaluate the pharmacokinetic behavior of cinnarizine in rats, a simple, rapid, sensitive, and environmentally friendly supercritical fluid chromatography-tandem mass spectrometric method was established and validated. In this method, flunarizine, a structural analogue of cinnarizine, was selected as the internal standard, and cinnarizine was extracted from rat plasma using evaporation-free liquid-liquid extraction method. The analytes were separated on a Torus 1-AA column (3.0 mm × 100 mm, 1.7 μm) within 2.0 min, using a gradient elution procedure. The transitions of cinnarizine and flunarizine were m/z 369.1 → 167.1 and m/z 405.1 → 203.1, respectively. Cinnarizine showed good linear correlation in the range of 1-500 ng/ml with a lower limit of quantification of 1 ng/ml. The intra- and interday precision and accuracy of all quality control samples were within ±15%. This high-throughput, accurate, sensitive, and reproducible method has been successfully applied to study the effects of the precipitation inhibitor cinnarizine on the pharmacokinetics in rats.

Effect of food intake on the pharmacokinetics of rivoceranib in healthy subjects

Rivoceranib is a selective inhibitor of VEGFR-2 being developed for the treatment of solid tumor. The objective of the study was to evaluate the effect of food on bioavailability as well as single- and multiple-dose pharmacokinetics (PKs) of 81 and 201 mg doses of rivoceranib. The study was conducted as a two-part study. In Part 1 (single ascending dose (SAD), open-label, crossover study design), 2 oral doses of rivoceranib (81 mg or 201 mg) were given to all healthy subjects with a minimum 3-day washout period between dosing. Part 2 was a multiple ascending dose (MAD), open-label, crossover design where subjects were divided based on 81 and 201 mg doses. Both doses were administered with and without food in a crossover manner for the SAD and MAD parts. 24 healthy subjects completed Part 1 and 20 subjects completed Part 2. For the 81 mg dose in the SAD and MAD parts of the study, their food effect was not observed. For the 201 mg dose in both parts, food appeared to increase bioavailability by 20%-30% in Part 1, and 30%-40% in Part 2. Median t_max value was delayed when rivoceranib was administered with food at each dose level in both parts of the study. Dose proportionality was confirmed only for the AUC_0-∞  value from Part 1-fasted cohort but inconclusive for C_max  and AUC parameters under other dosing regimens. In conclusion, rivoceranib when taken with food delays t_max appears to increase bioavailability at 201 mg dose.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.