Abstract
Green tea extract is a widely used dietary supplement. The objective of this study was to assess the influence of a decaffeinated green tea (DGT; Camellia sinensis) extract on the activity of the drug-metabolizing enzymes cytochrome P-450 2D6 and 3A4. Probe drugs dextromethorphan (30 mg, CYP2D6 activity) and alprazolam (ALPZ; 2 mg, CYP3A4 activity) were administered orally to healthy volunteers (n = 11) at baseline, and again after treatment with four DGT capsules/day for 14 days. Each DGT capsule contained 211 ± 25 mg of green tea catechins and <1 mg of caffeine. Dextromethorphan metabolic ratios (DMRs) and alprazolam pharmacokinetics were determined at baseline and after DGT treatment. There were no significant differences in ALPZ pharmacokinetics at baseline and after DGT treatment (all P values ≥ 0.05; maximum concentration in plasma, 33 ± 8 versus 34 ± 13 ng/ml; time to reach maximum concentration in plasma, 1.4 ± 1.2 versus 1.4 ± 1.2 h; area under the plasma concentration versus time curve, 480 ± 119 versus 510 ± 107 h · ng · ml-1; half-life of elimination, 12.3 ± 1.7 versus 13.1 ± 3.4 h). The DMR was 0.053 ± 0.045 at baseline and 0.041 ± 0.032 after DGT supplementation (P > 0.05). The plasma concentration of the green tea flavonoid, (-)-epigallocatechin gallate, reached 1.3 ± 1.8 μM 2 h after DGT treatment. Our results indicate that DGT is unlikely to alter the disposition of medications primarily dependent on the CYP2D6 or CYP3A4 pathways of metabolism.
Footnotes
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This publication was made possible by Grant R21 AT00511 from the National Center for Complementary and Alternative Medicine (NCCAM). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Center for Complementary and Alternative Medicine, National Institutes of Health. The authors gratefully acknowledge U.S. Public Health Service Grant M01 RR01070-18 for the funding of the clinical study at the Medical University of South Carolina General Clinical Research Center.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.104.000083.
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ABBREVIATIONS: EGCG, epigallocatechin gallate; ALPZ, alprazolam; DM, dextromethorphan; DMR, dextromethorphan to dextorphan metabolic ratio; DGT, decaffeinated green tea; P450, cytochrome P450; HPLC, high-performance liquid chromatography.
- Received April 1, 2004.
- Accepted May 26, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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