Screening of drug metabolizing enzymes for fusidic acid and its interactions with isoform-selective substrates in vitro.

1. Fusidic acid (FA) is widely used for the treatment of infections of sensitive osteomyelitis or skin and soft tissue caused by bacteria. However, the role of cytochrome P450s (CYPs) in the metabolism of FA is unclear. In the present study, we screened the main CYPs for the metabolism of FA and studied its interactions with isoform-selective substrates in vitro. 2. The main CYP450s were screened according to the inhibitory effect of specific inhibitors on the metabolism of FA in human liver microsomes (HLMs) or recombinant CYP isoforms. Enzyme kinetic parameters including Ki, Ki', Vmax, and IC50 were calculated to determine the potential of FA to affect CYP-mediated metabolism of isoform-selective substrates. 3. FA metabolism rate was inhibited by 49.8% and 83.1% under CYP2D6, CYP3A4 selective inhibitors in HLMs. In recombinant experiment, the inhibitory effects on FA metabolism were 83.3% for CYP2D6 and 58.9% for CYP3A4, respectively. FA showed inhibition on CYP2D6 and CYP3A4 with Kis of 13.9 and 38.6 µM, respectively. Other CYP isoforms including CYP1A2, CYP2A6, CYP2C9, CYP2E1, and CYP2C19 showed minimal or no effect on the metabolism of FA. 4. FA was primarily metabolized by CYP2D6 and CYP3A4 and showed a noncompetitive inhibition on CYP2D6 and a mixed competitive inhibition on CYP3A4. Drug-drug interactions between FA and other chemicals, especially with substrates of CYP2D6 and CYP3A4, are phenomena that clinicians need to be aware of and cautious about.

Effects of curcumin on the pharmacokinetics of talinolol in human with ABCB1 polymorphism.

This study was to investigate the effect of concomitantly administered curcumin on the pharmacokinetics of talinolol and association with ABCB1 C3435T genetic polymorphism. A two-phase, randomized, single-blind, crossover study was carried out in 18 healthy male volunteers with different genotypes of ABCB1, including C3435C (CC, n = 6), C3435T (CT, n = 6) and T3435T (TT, n = 6). The pharmacokinetics of talinolol were measured after co-administration of placebo or 1000 mg curcumin capsules once daily for 14 days. The AUC(0-48 h) and AUC(0-∞) of talinolol were increased by 67.0% (95% CI: 1.09~2.25; p = 0.002) and 80.8% (95% CI: 0.92~2.69; p = 0.005) respectively with curcumin co-administration. The C(max) of talinolol was significantly higher after curcumin administration as compared with placebo (p = 0.029).The CL/F of talinolol was decreased by 25.9% (p = 0.005) during the curcumin-treated phase. No significant change in t(max) and t(1/2) of talinolol were observed between the placebo- and curcumin-treated phases. AUC(0-48), AUC(0-∞), C(max) of talinolol were extensively increased and CL(oral)/F decreased in TT subjects. Co-administration of curcumin significantly increased the plasma concentration of talinolol in healthy volunteers. The effect of curcumin on talinolol was associated with ABCB1 genotypes (C3435T).

Effect of a traditional Chinese medicine Liu Wei Di Huang Wan on the activities of CYP2C19, CYP2D6 and CYP3A4 in healthy volunteers.

Liu Wei Di Huang Wan (LDW), a well-known traditional Chinese medicine, is widely used for the treatment of various diseases in China. This study was designed to investigate the potential herb-drug interactions of LDW in healthy volunteers and attempted to ascertain whether the interaction might be affected by genotypes. We assessed the effect of LDW on the activities of CYP2C19, CYP2D6 and CYP3A4 in 12 Chinese healthy subjects in a single-center, controlled, non-blinded, two-way crossover clinical trial. The subject pool consisted of six extensive metabolizers with CYP2C19*1/*1 and six poor metabolizers with CYP2C19*2/*2. Placebo or 4.8 g LDW (12 pills, 0.2 g/pill, twice daily) was given to each participant for 14 continuous days with a wash-out period of 2 weeks after an oral administration of 30 mg omeprazole, 30 mg dextromethorphan hydrobromide and 7.5 mg midazolam. The activities of CYP2C19, CYP2D6 and CYP3A4 were ascertained by their respective plasma or urinary metabolic ratios on day 14 post-treatment. There is no difference in the activities of the three tested enzymes before or after a 14-day administration of LDW. LDW had no effect on the pharmacokinetic parameters of the substrates and their metabolites. A 14-day administration of LDW did not affect the activities of CYP2C19, CYP2D6 and CYP3A4. LDW is unlikely to cause pharmacokinetic interaction when it is combined with other medications predominantly metabolized by these enzymes.

Clopidogrel inhibits CYP2C19-dependent hydroxylation of omeprazole related to CYP2C19 genetic polymorphisms.

This study explores the impact of clopidogrel on the pharmacokinetics of omeprazole related to CYP2C19 genetic polymorphisms. Twelve healthy volunteers (6 CYP2C19*1/*1, 5 CYP2C19*2/*2, and 1 CYP2C19*2/*3) are enrolled in a 2-phase randomized crossover trial. In each phase, the volunteers are administered a single oral dose of omeprazole 40 mg after pretreatment of either placebo or clopidogrel (300 mg on the first day and then 75 mg once daily for 3 consecutive days). Plasma concentrations of omeprazole and its metabolites are quantified by high-performance liquid chromatography with UV detection. After clopidogrel treatment, the AUC(0-infinity) of omeprazole increases by 30.02% +/- 18.03% (P = .004) and that of 5-hydroxyomeprazole decreases by 24.30% +/- 11.66% (P = .032) in CYP2C19*1/*1. The AUC(0-infinity) ratios of omeprazole to 5-hydroxyomeprazole increase by 74.98% +/- 35.48% (P = .001) and those of omeprazole to omeprazole sulfone do not change significantly (P = .832) in CYP2C19*1/*1. No significant alteration is observed in CYP2C19*2/*2 or *3. Clopidogrel inhibits CYP2C19-dependent hydroxylation of omeprazole in CYP2C19*1/*1 and has no impact on CYP3A4-catalyzed sulfoxidation of omeprazole.