title: Effects of Ginkgo biloba extract on the pharmacokinetics and pharmacodynamics of tolbutamide in protein-restricted rats.
abstract: OBJECTIVE
  Effects of repeated administration of Ginkgo biloba extract on pharmacokinetics and pharmacodynamics of tolbutamide were examined in rats fed a low-protein diet.
  
  
  METHODS
  Rats were given a low (7% casein) or control (20% casein) protein diet for 21 days and administered Ginkgo biloba extract (100mg/kg per day) for the last 5 days. Tolbutamide was co-administered on the last day. Blood glucose and plasma tolbutamide concentrations were determined over the subsequent 12h and the activity of hepatic cytochrome P450s were determined at 12h after dosing.
  
  
  RESULTS
  There were significant decreases in body weight, the ratio of liver to body weight, and plasma albumin concentrations in rats on the low-protein diet compared with controls. The hypoglycaemic effect of tolbutamide was significantly greater and the concentration of the drug in plasma was higher in the former group. The repeated administration of Ginkgo biloba extract had little influence on the hypoglycaemic effect of tolbutamide, but tended to decrease the drug concentration in plasma of control rats, while it reduced significantly the hypoglycaemic action and plasma concentration of tolbutamide in the protein-restricted rats.
  
  
  CONCLUSIONS
  The effects of Ginkgo biloba extract on the pharmacokinetics and pharmacodynamics of tolbutamide were significantly enhanced in rats on the low-protein diet.
authors.affiliation: Department of Pharmacokinetics and Pharmacodynamics and Global Center of Excellence (COE) Program, School of Pharmaceutical Sciences, University of Shizuoka, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Taki
authors.forename: Eri
authors.initials: E
authors.lastname: Hagiwara
authors.forename: Chiemi
authors.initials: C
authors.lastname: Hirose
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Shinozuka
authors.forename: Keizo
authors.initials: K
authors.lastname: Umegaki
authors.forename: Shizuo
authors.initials: S
authors.lastname: Yamada
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D002364:Caseins / Q000008:administration & dosage; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage; D020441:Ginkgo biloba; D041743:Herb-Drug Interactions; D007004:Hypoglycemic Agents / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects; D008297:Male; D009929:Organ Size / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012709:Serum Albumin / Q000378:metabolism; D014044:Tolbutamide / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D002364:Caseins; D004044:Dietary Proteins; D007004:Hypoglycemic Agents; D010936:Plant Extracts; D012709:Serum Albumin; D014044:Tolbutamide