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RESEARCH REPORTS |
1 Assistant Professor, College of Pharmacy & Health Sciences, Texas Southern University, Houston, TX
2 Professor/Head, Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL
3 Candidate, Department of Pharmacal Sciences, Harrison School of Pharmacy
4 Research Fellow, Department of Pharmacal Sciences, Harrison School of Pharmacy
* To whom correspondence should be addressed. E-mail: bellec{at}tsu.edu.
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Abstract |
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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.
Reprints: Dr. Bell, College of Pharmacy & Health Sciences, Texas Southern University, 3100 Cleburne St., Houston, TX 77004, fax 713/313-1901, bellec@tsu.edu
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