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COMPLEMENTARY AND ALTERNATIVE MEDICINE

Lack of Pharmacokinetic Interaction Between St. John's Wort and Prednisone

Assistant Professor, College of Pharmacy & Health Sciences, Texas Southern University, Houston, TX

William R Ravis, PhD FCP

Professor/Head, Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL

Hui Min Chan, PhD Candidate

Department of Pharmacal Sciences, Harrison School of Pharmacy

Yuh-Jing Lin

Research Fellow, Department of Pharmacal Sciences, Harrison School of Pharmacy

Reprints: Dr. Bell, College of Pharmacy & Health Sciences, Texas Southern University, 3100 Cleburne St., Houston, TX 77004, fax 713/313-1901, bellec{at}tsu.edu

BACKGROUND: St. John's wort (SJW) is a popular dietary supplement involved in numerous dietary supplement-drug interactions with prescription and non-prescription drugs. The supplement has been shown to affect the metabolism of various CYP3A4 substrates. The CYP3A4 pathway mediates the metabolism of a large number of drug entities, including the corticosteroids prednisone and prednisolone.

OBJECTIVE: To examine the effects of long-term SJW administration on the pharmacokinetics of prednisone and its reversible metabolite prednisolone in male subjects.

METHODS: Eight male subjects participated in this single-dose study. The pharmacokinetics of prednisone and prednisolone were evaluated before and after 28 days of SJW administration. Plasma corticosteroid concentrations were determined using a normal phase high-performance liquid chromatography assay. Model-independent methods were used to evaluate corticosteroid pharmacokinetics.

RESULTS: Twenty-eight days of SJW treatment resulted in no significant alterations in the pharmacokinetic parameters for prednisone or prednisolone. Oral administration of prednisone resulted in prednisone mean ± SD area under the curves (AUCs) of 115.89 ± 39.52 µg·h/L prior to SJW treatment and 128.76 ± 32.71 µg·h/L after 28 days of treatment. Prednisolone mean AUCs were 714.19 ± 153.29 µg·h/L before SJW administration and 700.74 ± 89.68 µg·h/L after treatment.

CONCLUSIONS: Concurrent administration of SJW had no significant effect on the single-dose pharmacokinetics of prednisone or metabolic prednisolone in male subjects.

Key Words: cytochrome, metabolism, prednisolone, prednisone, St. John's wort

Published Online, October 9, 2007. www.theannals.com, DOI 10.1345/aph.1K316