Ginkgo Biloba Research Today is a free monthly online journal that collates and summarizes the latest research about Ginkgo Biloba, including details on ginkgo biloba, herbal remedies, side effects, benefits.

Limitations of Using a Single Postdose Midazolam Concentration to Predict CYP3A-Mediated Drug Interactions.

Penzak SR, Busse KH, Robertson SM, Formentini E, Alfaro RM, Davey RT

National Institutes of Health.

Midazolam is a common probe used to predict CYP3A activity, but multiple blood samples are necessary to determine midazolam's area under the concentration-time curve (AUC). As such, single sampling strategies have been examined. The purpose of this study was to assess the ability of single midazolam concentrations to predict midazolam AUC in the presence and absence of CYP3A modulation by Ginkgo biloba extract (GBE). Subjects received oral midazolam 8 mg before and after 28 days of GBE administration. Postdose blood samples were collected during both study periods and midazolam AUC determined. Linear regression was used to generate measures of predictive performance for each midazolam concentration. The geometric mean ratio (90% confidence intervals) of midazolam AUC0-infinity post-GBE/AUC0-infinity pre-GBE was 0.66 (0.49-0.84) (P = .03). Before and after GBE administration, optimal midazolam sampling times were identified at 3.5 to 5 hours and 2 to 3 hours, respectively. Single midazolam concentrations between 2 and 5 hours correctly predicted the reduction in midazolam AUC following GBE exposure, but confidence intervals were generally wide. Intersubject variability in CYP3A activity (either inherent or from drug administration) alters the prediction of optimal midazolam sampling times; therefore, midazolam AUC is preferred for assessing CYP3A activity in drug-drug interaction studies.

Published 18 April 2008 in J Clin Pharmacol.
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