Drug Metabolism Letters - Volume 2, Issue 1, 2008

The aim of this article is to focus on the implementation and the application of matrix-assisted laser desorption/ ionization-imaging mass spectrometric system (MALDI-IMS) to determine the disposition or biotransformation pathway of terfenadine and its active metabolite, fexofenadine in mouse and rat whole-body tissue sections. Whole-body MALDI-IMS data showed that the poor oral bioavailability of terfe Read More

CYP3A isoforms account for about 30% of total hepatic P450s. Most statins have been accepted probes for CYP3A4. The metabolic ratio of atorvastatin/ortho-hydroxyatorvastatin showed a bimodal distribution with respect to metabolism of atorvastatin. These observations showed that the frequency of occurrence of the poor metabolizer phenotype is 2.4 % in the Gujarat subjects.

Membrane transporters are critical for the uptake as well as elimination of chemicals and by-products of metabolism from the liver and kidneys. Since these proteins are important determinants of chemical disposition, changes in their expression in different disease states can modulate drug pharmacokinetics. The present study investigated alterations in the renal and hepatic expression of organic anion and cation transporte Read More

Methylenetetrahydrofolate reductase (MTHFR) gene located on chromosome 1p36.3 catalyses the conversion of 5,10-methylenetetrahydrofolate to 5,methyltetrahydrofolate, the major methyl donor for the conversion of homocysteine to methionine. Two common polymorphisms in the MTHFR gene have been identified, 677C>T in exon 4, leading to substitution of alanine by valine and 1298A>C in exon 7 which leads to the repl Read More

The pharmacokinetic profile of ceftriaxone was studied in female healthy goats, induced hepatopathic and nephropathic goats after a single intravenous dose at 50 mg kg-1. Ceftriaxone persisted for 2 h in plasma of hepatopathic goats compared to 1 h of healthy goats, but the kinetic behaviour followed ‘one-compartment open model’ in both healthy and hepatopathic goats. Mean value of t½β (0.32 ± 0.008 h) was sig Read More

Flubendazole (FLU) is a widely administered benzimidazole anthelmintic indicated for the control of parasitic diseases in farm animals including pigs and pheasants. This study was designed to test the biotransformation of FLU in control animals and animals treated with FLU in recommended therapeutic doses. The activities of several pheasant and porcine hepatic and intestinal carbonyl reducing enzymes and their modulatio Read More

High resolution accurate MS with an LTQ-Orbitrap identified two novel metabolites of diclofenac in rat bile and rat and human hepatocyte incubations: a benzyl-S-glutathione conjugate and 2-(2,6-dichlorophenylamino) benzoic acid. A mechanism for the bioactivation of diclofenac involving decarboxylation is proposed.

This study evaluated the reproducibility, sensitivity, accuracy, and precision of stop-flow liquid radiochromatographic detection (RFD). Stop-flow RFD was about 10-fold more sensitive compared with traditional RFD and had a good reproducibility for quantification and HPLC retention time. Stop-flow RFD was applied to determine enzyme kinetics of radiolabeled drugs. The enzyme kinetic parameters of muraglitazar glucuronidati Read More

Doxorubicin is one of the most effective anti-tumour agent. To clarify whether a single dose produces its effects soon after dosing or only after hours or days and whether the effects are brief or prolonged, time-dose relationships were explored by calculating lethal time (LT50) values which is a statistical estimate of the time from dosage to death of 50% of the organisms/ or cells in a very large population subjected to a toxic Read More

The relationship between time-dependent inactivation (TDI) and IC50 is examined using a consolidated method for evaluating CYP450 inhibition during drug discovery. An IC50 fold-shift of >1.5 indicated significant TDI potency. Further, the “shifted IC50” could be used to estimate, the KI and TDI potency ratio kinact/KI to within 2-fold in most cases.

Ginkgo biloba is one of the most popular herbal medicines in the world, due to its purported pharmacological effects, including memory-enhancing, cognition-improving, and antiplatelet effects. The study aimed to investigate the activity and expression of cytochrome P450 (CYP) 3A in human and rat primary hepatocytes treated with standardized G. biloba extract (100, 500, and 2500 ng/ml) for 72 hr, and to measure the protein ex Read More

The new analgesic tapentadol was evaluated for induction and inhibition of several cytochrome P450 enzymes in vitro, and protein binding was assessed. It was concluded that no clinically relevant drug-drug interactions are likely to occur through either mechanism.