title: Effect of oral ketoconazole on first-pass effect of nifedipine after oral administration in dogs.
abstract: The long-term oral ketoconazole (KTZ) treatment extensively inhibits hepatic CYP3A activity. We investigated the effect of the KTZ treatment on hepatic and intestinal extraction of nifedipine (NIF) using beagle dogs. Four dogs were given orally KTZ for 20 days (200 mg, bid). NIF was administered either intravenously (0.5 mg/kg) or orally (20 mg) 10 and 20 days before the KTZ treatment and 10 and 20 days after start of KTZ treatment. CLtot of NIF after intravenous administration decreased to about 50% during the KTZ treatment. C(max) and AUC after oral administration increased to 2.5-fold and fourfold, respectively, by the KTZ treatment. The hepatic extraction ratio of NIF decreased to about a half by KTZ. A significant decrease in intestinal extraction ratio was not observed. In conclusion, the KTZ treatment inhibits hepatic extraction more profoundly than intestinal extraction of NIF. Therefore, inhibition of hepatic extraction of NIF by the KTZ treatment mainly results in substantial increase in systemic bioavailability in dogs. Because KTZ inhibits human CYP3A activities similar to canine CYP3A activities, the long-term oral KTZ treatment may dramatically increase bioavailability of NIF or other CYP3A substrates in humans.
authors.affiliation: Department of Veterinary Medicine, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-0054, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Kuroha
authors.forename: Hideki
authors.initials: H
authors.lastname: Kayaba
authors.forename: Shizuka
authors.initials: S
authors.lastname: Kishimoto
authors.forename: Waleed F
authors.initials: WF
authors.lastname: Khalil
authors.forename: Minoru
authors.initials: M
authors.lastname: Shimoda
authors.forename: Eiichi
authors.initials: E
authors.lastname: Kokue
mesh_terms: D000284:Administration, Oral; D000465:Algorithms; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases; D002121:Calcium Channel Blockers / Q000493:pharmacokinetics*; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D004285:Dogs; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006207:Half-Life; D007275:Injections, Intravenous; D007413:Intestinal Mucosa / Q000378:metabolism; D007654:Ketoconazole / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D008297:Male; D009543:Nifedipine / Q000493:pharmacokinetics*; D010089:Oxidoreductases, N-Demethylating / Q000037:antagonists & inhibitors; D013607:Tablets
chemical_list: D000935:Antifungal Agents; D002121:Calcium Channel Blockers; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D013607:Tablets; D001189:Aryl Hydrocarbon Hydroxylases; D051544:Cytochrome P-450 CYP3A; D010089:Oxidoreductases, N-Demethylating; D009543:Nifedipine; D007654:Ketoconazole