title: Effects of Ginkgo biloba extracts on diazepam metabolism: a pharmacokinetic study in healthy Chinese male subjects.
abstract: OBJECTIVE
  It has been reported that Ginkgo biloba extract (GBE) is an inducer or inhibitor of microsomal cytochrome P450 (CYP) 2C19, and diazepam is a substrate of CYP2C19. Thus, it could be expected that GBE may alter the metabolism of diazepam.
  
  
  METHODS
  The pharmacokinetic parameters of diazepam and one of its metabolites, N-demethyldiazepam, were compared after oral administration of diazepam (10 mg) in the absence or presence of oral GBE (120 mg bid, for 28 days) in 12 healthy volunteers. The pharmacokinetic analysis was performed using a noncompartmental method.
  
  
  RESULTS
  The 90% confidence intervals (CIs) of the ratios of mean pharmacokinetic parameters of diazepam presence and absence of GBE were well within the 80-125% bioequivalence range, indicating no pharmacokinetic interaction. The ratio of AUC(0-408) with GBE to AUC(0-408) without GBE was 95.2 (90%CI: 91.6-98.8) and 101.8 (90%CI: 99.4-104.1) for diazepam and N-desmethyldiazepam, respectively. The two drugs were well tolerated, and no drug-related serious adverse events were reported.
  
  
  CONCLUSIONS
  The above data suggest that GBE, when taken in normally recommended doses over a 4-week time period, may not affect the pharmacokinetics of diazepam via CYP2C19 and the excretion of N-desmethyldiazepam in healthy volunteers. No drug-drug interaction was observed between GBE and diazepam.
authors.affiliation: Clinical Pharmacy and Pharmacology Research Institute, Third Xiangya Hospital, Central South University, Changsha, 410013, China.
authors.forename: Xiao-Cong
authors.initials: XC
authors.lastname: Zuo
authors.forename: Bi-Kui
authors.initials: BK
authors.lastname: Zhang
authors.forename: Su-Jie
authors.initials: SJ
authors.lastname: Jia
authors.forename: Shi-Kun
authors.initials: SK
authors.lastname: Liu
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Zhou
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Dai
authors.forename: Ben-Mei
authors.initials: BM
authors.lastname: Chen
authors.forename: Guo-Ping
authors.initials: GP
authors.lastname: Yang
authors.forename: Hong
authors.initials: H
authors.lastname: Yuan
mesh_terms: D044466:Asian People; D003975:Diazepam / Q000493:pharmacokinetics*; D020441:Ginkgo biloba; D041743:Herb-Drug Interactions; D006801:Humans; D006854:Hydrocortisone / Q000031:analogs & derivatives / Q000652:urine; D008297:Male; D010936:Plant Extracts / Q000009:adverse effects*; D011794:Quercetin / Q000097:blood; D055815:Young Adult
chemical_list: D010936:Plant Extracts; C001380:6 beta-hydroxycortisol; D011794:Quercetin; D003975:Diazepam; D006854:Hydrocortisone