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Randomized Controlled Trial
. 2006 Feb;46(2):201-13.
doi: 10.1177/0091270005284854.

Assessing the clinical significance of botanical supplementation on human cytochrome P450 3A activity: comparison of a milk thistle and black cohosh product to rifampin and clarithromycin

Bill Gurley  1 , Martha A Hubbard, D Keith Williams, John Thaden, Yudong Tong, W Brooks Gentry, Philip Breen, Danielle J Carrier, Shreekar Cheboyina
Affiliations
Randomized Controlled Trial

Assessing the clinical significance of botanical supplementation on human cytochrome P450 3A activity: comparison of a milk thistle and black cohosh product to rifampin and clarithromycin

Bill Gurley et al. J Clin Pharmacol. 2006 Feb.

Abstract

Phytochemical-mediated modulation of cytochrome P450 enzymes (CYPs) may underlie many herb-drug interactions. This study's purpose was to assess the effects of milk thistle and black cohosh supplementation on CYP3A activity and compare them to a clinically recognized inducer, rifampin, and inhibitor, clarithromycin. Healthy volunteers were randomly assigned to receive a standardized milk thistle (900 mg) or black cohosh (80 mg) supplement for 14 days. Subjects also received rifampin (600 mg) and clarithromycin (1000 mg) for 7 days as positive controls for CYP3A induction and inhibition, respectively. Midazolam was administered orally before and after each supplementation and control period. The effects of milk thistle, black cohosh, rifampin, and clarithromycin on midazolam pharmacokinetics were determined using noncompartmental techniques. Unlike those observed for rifampin and clarithromycin, midazolam pharmacokinetics was unaffected by milk thistle or black cohosh. Milk thistle and black cohosh appear to have no clinically relevant effect on CYP3A activity in vivo.

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Figures

Figure 1
Figure 1
Midazolam concentration-time profiles before and after clarithromycin. rifampin, milk thistle and black cohosh. Black squares = baseline values; gray circles = post-supplementation/medication values. Error bars = standard deviations.
Figure 2
Figure 2
Comparison of pre- and post-supplementation phenotypic ratios (1-hydroxymidazolam/midazolam) for CYP3A4. (A) Rifampin, (B) Clarithromycin, (C) Milk thistle, (D) Black cohosh. Gray circles = individual values; Black circles = group means. Asterisks = statistically significant difference from baseline.
Figure 3
Figure 3
Plot of 1-hour 1′-hydroxymidazolam/midazolam phenotypic ratios versus midazolam oral clearance (CL/F/kg).
See this image and copyright information in PMC

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