In Vitro and In Vivo Assessment of Metabolic Drug Interaction Potential of Dutasteride with Ketoconazole

Investigation of the factors responsible for the low oral bioavailability of alizarin using a sensitive LC-MS/MS method: In vitro, in situ, and in vivo evaluations

Alizarin (1,2-dihydroxyanthraquinone) is an anthraquinone reddish dye widely used for painting and textile dyeing. As the biological activity of alizarin has recently attracted increasing attention from researchers, its therapeutic potential as complementary and alternative medicine is of interest. However, no systematic research has been conducted on the biopharmaceutical and pharmacokinetic aspects of alizarin. Therefore, this study aimed to comprehensively investigate the oral absorption and intestinal/hepatic metabolism of alizarin using a simple and sensitive tandem mass spectrometry method developed and validated in-house. The present method for the bioanalysis of alizarin has merits, including a simple pretreatment procedure, small sample volume, and adequate sensitivity. Alizarin exhibited pH-dependent moderate lipophilicity and low solubility with limited intestinal luminal stability. Based on the in vivo pharmacokinetic data, the hepatic extraction ratio of alizarin was estimated to be 0.165-0.264, classified as a low level of hepatic extraction. In an in situ loop study, considerable fractions (28.2%-56.4%) of the alizarin dose were significantly absorbed in gut segments from the duodenum to ileum, suggesting that alizarin may be classified as the Biopharmaceutical Classification System class II. An in vitro metabolism study using rat and human hepatic S9 fractions revealed that glucuronidation and sulfation, but not NADPH-mediated phase I reactions and methylation, are significantly involved in the hepatic metabolism of alizarin. Taken together, it can be estimated that the fractions of oral alizarin dose unabsorbed from the gut lumen and eliminated by the gut and liver before reaching the systemic circulation are 43.6%-76.7%, 0.474%-36.3%, and 3.77%-5.31% of the dose, respectively, resulting in a low oral bioavailability of 16.8%. Therefore, the oral bioavailability of alizarin depends primarily on its chemical degradation in the gut lumen and secondarily on first-pass metabolism.

LC-MS/MS determination of dutasteride and its major metabolites in human plasma

Dutasteride is a specific and selective inhibitor of both 5α-reductase isoforms used mainly in benign prostatic hyperplasia and lower urinary tract symptoms. Although the drug is extensively metabolized in humans, data on the concentrations of its main metabolites are lacking. There is also a lack of data on dutasteride stability in frozen plasma samples. Our method was used to determine dutasteride and its active metabolites: 4'-hydroxydutasteride, 6β-hydroxydutasteride, and 1,2-dihydrodutasteride in plasma after a single administration of 0.5 mg of dutasteride. We also assessed the long-term stability (two years in the freezer) of dutasteride in clinical samples. The developed method covered the range of 0.1-3.5 ng/mL for dutasteride and 0.08-1.2 ng/mL for 1,2-dihydrodutasteride, 4'-hydroxydutasteride, 6β-hydroxydutasteride. It was proved to be reliable as it met all validation criteria required by the European Medicine Agency for bioanalytical methods. 4'-hydroxydutasteride and 1,2-dihydrodutasteride concentrations in plasma were higher than 6β-hydroxydutasteride. Dutasteride was stable in the freezer for up to 2 years in clinical samples. Thus within 1014 days of storage (below - 65 °C), samples can be reanalyzed without the risk of unreliable results.

Assessment of Metabolic Interaction between Repaglinide and Quercetin via Mixed Inhibition in the Liver: In Vitro and In Vivo

Repaglinide (RPG), a rapid-acting meglitinide analog, is an oral hypoglycemic agent for patients with type 2 diabetes mellitus. Quercetin (QCT) is a well-known antioxidant and antidiabetic flavonoid that has been used as an important ingredient in many functional foods and complementary medicines. This study aimed to comprehensively investigate the effects of QCT on the metabolism of RPG and its underlying mechanisms. The mean (range) IC₅₀ of QCT on the microsomal metabolism of RPG was estimated to be 16.7 (13.0–18.6) μM in the rat liver microsome (RLM) and 3.0 (1.53–5.44) μM in the human liver microsome (HLM). The type of inhibition exhibited by QCT on RPG metabolism was determined to be a mixed inhibition with a K_i of 72.0 μM in RLM and 24.2 μM in HLM as obtained through relevant graphical and enzyme inhibition model-based analyses. Furthermore, the area under the plasma concentration versus time curve (AUC) and peak plasma concentration (C_max) of RPG administered intravenously and orally in rats were significantly increased by 1.83- and 1.88-fold, respectively, after concurrent administration with QCT. As the protein binding and blood distribution of RPG were observed to be unaltered by QCT, it is plausible that the hepatic first-pass and systemic metabolism of RPG could have been inhibited by QCT, resulting in the increased systemic exposure (AUC and C_max) of RPG. These results suggest that there is a possibility that clinically significant pharmacokinetic interactions between QCT and RPG could occur, depending on the extent and duration of QCT intake from foods and dietary supplements.

Pharmacokinetic Drug-Drug Interactions and Herb-Drug Interactions

Due to the growing use of herbal supplementation-ease of taking herbal supplements with therapeutics drugs (i [...].

Innovation in bioanalytical strategies and in vitro drug-drug interaction study approaches in drug discovery

Failure to evaluate actual toxicities of investigational molecules in drug discovery is majorly due to inadequate evaluation of their pharmacokinetics. Limitation of conventional drug metabolism profiling procedure demands advancement of existing approaches. Various techniques such as 3D cell culture system, bio microfluidic OoC model, sandwich culture model is in pipeline to be employed at their full potential in drug discovery phase. Although they outweigh the conventional techniques in various aspects, a more detailed exploration of applicability in terms of automation and high throughput analysis is required. This review extensively discusses various ongoing innovations in bioanalytical techniques. The review also proposed various scientific strategies to be adopted for prior assessment of interaction possibilities in translational drug discovery research.

Investigation of the Factors Responsible for the Poor Oral Bioavailability of Acacetin in Rats: Physicochemical and Biopharmaceutical Aspects

Acacetin, an important ingredient of acacia honey and a component of several medicinal plants, exhibits therapeutic effects such as antioxidative, anticancer, anti-inflammatory, and anti-plasmodial activities. However, to date, studies reporting a systematic investigation of the in vivo fate of orally administered acacetin are limited. Moreover, the in vitro physicochemical and biopharmaceutical properties of acacetin in the gastrointestinal (GI) tract and their pharmacokinetic impacts remain unclear. Therefore, in this study, we aimed to systematically investigate the oral absorption and disposition of acacetin using relevant rat models. Acacetin exhibited poor solubility (≤119 ng/mL) and relatively low stability (27.5–62.0% remaining after 24 h) in pH 7 phosphate buffer and simulated GI fluids. A major portion (97.1%) of the initially injected acacetin dose remained unabsorbed in the jejunal segments, and the oral bioavailability of acacetin was very low at 2.34%. The systemic metabolism of acacetin occurred ubiquitously in various tissues (particularly in the liver, where it occurred most extensively), resulting in very high total plasma clearance of 199 ± 36 mL/min/kg. Collectively, the poor oral bioavailability of acacetin could be attributed mainly to its poor solubility and low GI luminal stability.