title: Lack of inhibitory effects of several fluoroquinolones on cytochrome P-450 3A activities at clinical dosage in dogs.
abstract: Inhibitory effects of several fluoroquinolones (FQs) on liver CYP3A activities were examined by in vitro and in vivo tests in dogs. Midazolam (MDZ) hydroxylation rate was used to determine the CYP3A activities in liver microsomes. Enrofloxacin (EFX), ofloxacin (OFX) orbifloxacin (OBFX) and ciprofloxacin (CFX) were tested. None of the FQs changed Vmax, Km or intrinsic clearance (Vmax/Km) of MDZ. For in vivo test, we examined the effects of oral administration of EFX and OFX on the pharmacokinetics of quinidine (QN), a CYP3A substrate. EFX or OFX (10 mg/kg) was administered once a day for 3 days. QN (2 mg/kg) was intravenously injected at 2 h after the final dose of FQs administration. The same dose of QN was intravenously injected 3 weeks before the start of FQs administration for control. Neither EFX nor OFX changed the pharmacokinetic parameters of QN. These in vitro and in vivo consisted results suggest that these FQs lack the inhibitory effects on CYP3A activities in dogs. Hence, given these results, the risk of drug-drug interaction is unlikely to occur between FQs and CYP3A substrates in clinical situation in dogs.
authors.affiliation: Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: N L
authors.initials: NL
authors.lastname: Regmi
authors.forename: A M
authors.initials: AM
authors.lastname: Abd El-Aty
authors.forename: R
authors.initials: R
authors.lastname: Kubota
authors.forename: S S
authors.initials: SS
authors.lastname: Shah
authors.forename: M
authors.initials: M
authors.lastname: Shimoda
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D002939:Ciprofloxacin / Q000031:analogs & derivatives / Q000097:blood / Q000494:pharmacology; D051544:Cytochrome P-450 CYP3A / Q000187:drug effects*; D065692:Cytochrome P-450 CYP3A Inhibitors; D004285:Dogs; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D015242:Ofloxacin / Q000097:blood / Q000494:pharmacology; D011802:Quinidine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics
chemical_list: D000890:Anti-Infective Agents; D065692:Cytochrome P-450 CYP3A Inhibitors; D024841:Fluoroquinolones; D000077422:Enrofloxacin; D002939:Ciprofloxacin; C095163:orbifloxacin; D015242:Ofloxacin; D051544:Cytochrome P-450 CYP3A; D011802:Quinidine