title: Effects of repeated green tea catechin administration on human cytochrome P450 activity.
abstract: OBJECTIVE
  Preclinical studies suggested that green tea or green tea catechins can modulate the activities of drug-metabolizing enzymes. We conducted this clinical study to determine the effect of repeated green tea catechin administration on human cytochrome P450 (CYP) enzyme activities.
  
  
  METHODS
  Forty-two healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, study participants received a cocktail of CYP metabolic probe drugs, including caffeine, dextromethorphan, losartan, and buspirone for assessing the activity of CYP1A2, CYP2D6, CYP2C9, and CYP3A4, respectively. Blood and urine samples before and 8 h after probe drug administration were collected to determine parent drug and metabolite concentrations for measurements of baseline CYP enzyme activities. Following the baseline evaluation, study participants underwent 4 weeks of green tea catechin intervention at a dose that contains 800 mg epigallocatechin gallate (EGCG) daily. The green tea catechin product was taken on an empty stomach to optimize the p.o. bioavailability of EGCG. The EGCG dose given in this study exceeded the amounts provided by average green tea consumption. Upon completion of the green tea catechin intervention, the postintervention CYP enzyme activities were evaluated as described above.
  
  
  RESULTS
  There are large between-subject variations in CYP enzyme activities in healthy individuals. Four weeks of green tea catechin intervention did not alter the phenotypic indices of CYP1A2, CYP12D6, and CYP12C9, but resulted in a 20% increase (P = 0.01) in the area under the plasma buspirone concentration-time profile, suggesting a small reduction in CYP3A4 activity.
  
  
  CONCLUSIONS
  We conclude that repeated green tea catechin administration is not likely to result in clinically significant effects on the disposition of drugs metabolized by CYP enzymes.
authors.affiliation: Arizona Cancer Center, The University of Arizona, Tucson, AZ 85724, USA. schow@azcc.arizona.edu
authors.forename: H-H Sherry
authors.initials: HH
authors.lastname: Chow
authors.forename: Iman A
authors.initials: IA
authors.lastname: Hakim
authors.forename: Donna R
authors.initials: DR
authors.lastname: Vining
authors.forename: James A
authors.initials: JA
authors.lastname: Crowell
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Cordova
authors.forename: Wade M
authors.initials: WM
authors.lastname: Chew
authors.forename: Min-Jian
authors.initials: MJ
authors.lastname: Xu
authors.forename: Chiu-Hsieh
authors.initials: CH
authors.lastname: Hsu
authors.forename: James
authors.initials: J
authors.lastname: Ranger-Moore
authors.forename: David S
authors.initials: DS
authors.lastname: Alberts
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D028241:Camellia sinensis; D002392:Catechin / Q000493:pharmacokinetics*; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013662:Tea
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D013662:Tea; D002392:Catechin; D003577:Cytochrome P-450 Enzyme System; D019389:Cytochrome P-450 CYP2D6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human