title: Pharmacokinetics of intravenous, plain oral and enteric-coated oral omeprazole in the horse.
abstract: The objectives were to document the pharmacokinetics of intravenous, enteric-coated oral and plain oral omeprazole in fasted horses and to investigate the impact of feeding on the bioavailability of an enteric-coated omeprazole. Twelve horses received four treatments: intravenous omeprazole (0.5 mg/kg) in the fasted state (IV-Fasted), enteric-coated omeprazole (4 mg/kg) orally in the fasted state (ECO-Fasted), enteric-coated omeprazole (4 mg/kg) orally in the fed state (ECO-Fed) and plain omeprazole (4 mg/kg) orally in the fasted state (PL-Fasted). Plasma omeprazole concentrations were determined by UHPLC-MS. Bioavailability was higher (P = 0.038) in the ECO-Fasted group (21.5 [9.0-27.7]%) than the PL-Fasted group (10.1 [7.7-13.3]%). Similarly, AUC0-∞ was higher in the ECO-Fasted group than the PL-Fasted group (P = 0.027). No significant differences were present between the ECO-Fasted and ECO-Fed groups with regards to bioavailability, Cmax , Tmax or AUC0-∞ . When the half-life data from the oral formulations was pooled, it was longer than that observed in the IV-Fasted group (100 [73-118] min) and 35 [34-39] min, respectively; P < 0.0001). Bioavailability of enteric-coated omeprazole was higher than previously reported and feeding had minimal impact. Bioavailability of plain omeprazole was approximately half that of enteric-coated omeprazole. The longer half-life observed following oral administration was consistent with the flip-flop effect and has not previously been described for omeprazole in the horse.
authors.affiliation: School of Veterinary Sciences, The University of Queensland, Gatton, Qld, Australia.
authors.forename: B W
authors.initials: BW
authors.lastname: Sykes
authors.forename: C
authors.initials: C
authors.lastname: Underwood
authors.forename: C M
authors.initials: CM
authors.lastname: McGowan
authors.forename: P C
authors.initials: PC
authors.lastname: Mills
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000897:Anti-Ulcer Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019540:Area Under Curve; D018592:Cross-Over Studies; D005260:Female; D006207:Half-Life; D006736:Horses / Q000097:blood / Q000378:metabolism*; D007275:Injections, Intravenous; D008297:Male; D009853:Omeprazole / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000897:Anti-Ulcer Agents; D009853:Omeprazole