Regional Intestinal Drug Absorption: Biopharmaceutics and Drug Formulation

In vitro release and bioaccessibility of oral solid preparations in a dynamic gastrointestinal system simulating fasted and fed states: A case study of metformin hydrochloride tablets

Food and formulation characteristics are crucial factors affecting the gastrointestinal release and absorption kinetics of oral solid preparations. In the present study, the dynamic continuous release and bioaccessibility of metformin hydrochloride immediate-release (IR) and sustained-release (SR) tablets were investigated in the dynamic human stomach-intestine (DHSI-IV) system simulating fasted and fed states in healthy adults. Both tablet formulations (particularly IR tablet) exhibited a postponed release in the fed state compared to the fasted state. Correspondingly, the bioaccessible fraction of metformin from IR tablets in the presence of high-fat meal was significantly reduced to 76.2 % of the fasted state. However, the in vitro bioaccessibility was less impaired by food for SR tablets with a fed/fasted ratio of 95.5 %. A convolution-based approach was used to convert in vitro bioaccessibility results to plasma concentration data. The predicted plasma concentration curve showed good agreement with human data in terms of pharmacokinetic (PK) parameters. In the fasted state, the predicted Cmax, Tmax and AUC0-24h of IR tablets were 943.9 ± 25.7 ng/mL, 2.0 ± 0.4 h and 7090.7 ± 112.0 ng.h/mL, respectively, mirroring values observed in healthy subjects. Overall, the DHSI-IV system has demonstrated potential to assess and predict the impact of meal intake on the in vivo release and absorption behaviors of oral solid preparations.

Solubility-enabling formulations for oral delivery of lipophilic drugs: considering the solubility-permeability interplay for accelerated formulation development

INTRODUCTION

Tackling low water solubility of drug candidates is a major challenge in today's pharmaceutics/biopharmaceutics, especially by means of modern solubility-enabling formulations. However, drug absorption from these formulations oftentimes remains unchanged or even decreases, despite substantial solubility enhancement.

AREAS COVERED

In this article, we overview the simultaneous effects of the formulation on the solubility and the apparent permeability of the drug, and analyze the contribution of this solubility-permeability interplay to the success/failure of the formulation to increase the overall absorption and bioavailability. Three different patterns of interplay were identified: (1) solubility-permeability tradeoff in which every solubility gain comes with a price of concomitant permeability loss; (2) an advantageous interplay pattern in which the permeability remains unchanged alongside the solubility gain; and (3) an optimal interplay pattern in which the formulation increases both the solubility and the permeability. Passive vs. active intestinal permeability considerations in the context of the solubility-permeability interplay are also thoroughly discussed.

EXPERT OPINION

The solubility-permeability interplay pattern of a given formulation has a critical effect on its overall success/failure, and hence, taking into account both parameters in solubility-enabling formulation development is prudent and highly recommended.

Exploration of CviR-mediated quorum sensing inhibitors from Cladosporium spp. against Chromobacterium violaceum through computational studies

An opportunistic human pathogenic bacterium, Chromobacterium violaceum resists the potency of most antibiotics by exploiting the quorum sensing system within their community to control virulence factor expression. Therefore, blocking the quorum sensing mechanism could help to treat several infectious caused by this organism. The quorum sensing receptor (CviR) of C. violaceum was used as a model target in the current investigation to identify potentially novel quorum sensing inhibitors from Cladosporium spp. through in silico computational approaches. The molecular docking results confirmed the anti-quorum sensing potential of bioactive compounds from Cladosporium spp. through binding to CviR with varying docking scores between - 5.2 and - 9.5 kcal/mol. Relative to the positive control [Azithromycin (- 7.4 kcal/mol)], the top six metabolites of Cladosporium spp. had higher docking scores and were generally greater than - 8.5 kcal/mol. The thermodynamic stability and binding affinity refinement of top-ranked CviR inhibitors were further studied through a 160 ns molecular dynamic (MD) simulation. The Post-MD simulation analysis confirmed the top-ranked compounds' affinity, stability, and biomolecular interactions with CviR at 50 ns, 100 ns, and 160 ns with Coniochaetone K of the Cladosporium spp. having the highest binding free energy (- 30.87 kcal/mol) and best interactions (two consistent hydrogen bond contact) following the 160 ns simulation. The predicted pharmacokinetics properties of top selected compounds point to their drug likeliness, potentiating their chance as a possible drug candidate. Overall, the top-ranked compounds from Cladosporium spp., especially Coniochaetone K, could be identified as potential C. violaceum CviR inhibitors. The development of these compounds as broad-spectrum antibacterial medicines is thus possible in the future following the completion of further preclinical and clinical research.

Prediction of permeability across intestinal cell monolayers for 219 disparate chemicals using in vitro experimental coefficients in a pH gradient system and in silico analyses by trivariate linear regressions and machine learning

For medicines, the apparent membrane permeability coefficients (P_app) across human colorectal carcinoma cell line (Caco-2) monolayers under a pH gradient generally correlate with the fraction absorbed after oral intake. Furthermore, the in vitro P_app values of 29 industrial chemicals were found to have an inverse association with their reported no-observed effect levels for hepatotoxicity in rats. In the current study, we expanded our influx permeability predictions for the 90 previously investigated chemicals to both influx and efflux permeability predictions for 207 diverse primary compounds, along with those for 23 secondary compounds. Trivariate linear regression analysis found that the observed influx and efflux logP_app values determined by in vitro experiments significantly correlated with molecular weights and the octanol-water distribution coefficients at apical and basal pH levels (pH 6.0 and 7.4, respectively) (apical to basal, r = 0.76, n = 198; and basal to apical, r = 0.77, n = 202); the distribution coefficients were estimated in silico. Further, prediction accuracy was enhanced by applying a light gradient boosting machine learning system (LightGBM) to estimate influx and efflux logP_app values that incorporated 17 and 19 in silico chemical descriptors (r = 0.83-0.84, p < 0.001). The determination in vitro and/or prediction in silico of permeability coefficients across intestinal cell monolayers of a diverse range of industrial chemicals/food components/medicines could contribute to the safety evaluations of oral intakes of general chemicals in humans. Such new alternative methods could also reduce the need for animal testing during toxicity assessment.