Green tea (Camellia sinensis)
Green tea (Camellia sinensis) extract does not alter cytochrome P450 3A4 or 2D6 activity in healthy volunteers.
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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 microM 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.
1 . In vivo NPDI experiment (id=NPDI-_MbFQg)
In Vivo Interaction Study
No Effect (based on bioequivalence limits) was detected.
alprazolam 781039
- CYP3A4 4306811
Results
| Sample | Compound measured | Value | Measurement | Study sequence | Additional information | N replicates |
|---|
Experimental Conditions
Fixed-sequence
Healthy volunteers
Nonsmokers
CYP2D6 normal metabolizer
11
six women and five men; seven white; two Asian, two black, with a mean (+/- S.D.) age of 35 +/- 9 years
0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, 48, and 60 h
0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, 48, and 60 h
Drug or Natural Product Administration
Oral
tablet
2 mg
single dose, before and after administration of green tea extract
Oral
Capsule of Decaffeinated Super Green Tea Extract
844 mg of green tea catechins and <4 mg of caffeine
4 capsules/day
14 days
Life Extension; Fort Lauderdale, FL
No
2003
2 . CYP2D6 inhibition experiment (id=NPDI-cY8J6A)
In Vivo Interaction Study
No Effect (based on bioequivalence limits) was detected.
- CYP2D6 4173631
Results
| Sample | Compound measured | Value | Measurement | Study sequence | Additional information | N replicates |
|---|
Experimental Conditions
Fixed-sequence
Healthy volunteers
Nonsmokers
CYP2D6 normal metabolizer
11
six women and five men; seven white; two Asian, two black, with a mean (+/- S.D.) age of 35 +/- 9 years
0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, 48, and 60 h
0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, 48, and 60 h
Drug or Natural Product Administration
Oral
suspension (Robitussin cough syrup; Wyeth-Ayerst, Princeton, NJ)
30 mg
single dose, before and after administration of green tea extract
Oral
Capsule of Decaffeinated Super Green Tea Extract
844 mg of green tea catechins and <4 mg of caffeine
4 capsules/day
14 days
Life Extension; Fort Lauderdale, FL
No
2003