The effect of β-carotene supplementation on the pharmacokinetics of nelfinavir and its active metabolite M8 in HIV-1-infected patients.

β-Carotene supplements are often taken by individuals living with HIV-1. Contradictory results from in vitro studies suggest that β-carotene may inhibit or induce cytochrome P450 enzymes and transporters. The study objective was to investigate the effect of β-carotene on the steady-state pharmacokinetics of nelfinavir and its active metabolite M8 in HIV-1 infected individuals.

Time-dependent interaction between lopinavir/ritonavir and fexofenadine.

This study investigated the effect of single-dose and steady-state lopinavir/ritonavir on the exposure to fexofenadine, as a measure of P-glycoprotein activity. Sixteen volunteers (8 women) received single-dose oral fexofenadine 120 mg alone, in combination with single-dose ritonavir 100 mg or lopinavir/ritonavir 400/100 mg (randomized 1:1, stratified by sex), and in combination with steady-state lopinavir/ritonavir 400/100 mg twice daily. Single-dose ritonavir and lopinavir/ritonavir increased the area under the fexofenadine plasma concentration-time curve from 0 to infinity (AUC(infinity)) by 2.

Effect of high-dose vitamin C on hepatic cytochrome P450 3A4 activity.

Study Objectives: To investigate the effect of high-dose vitamin C on cytochrome P450 (CYP) 3A4 activity, and to evaluate possible sex-specific effects on CYP3A4 activity.

Design: Single-center longitudinal study.

Setting: Tertiary- and specialty-care teaching hospital.