(E76) A Preliminary Investigation of the Pharmacokinetics of Esomeprazole After Intravenous and Oral Dosing in Horses

Abstract: While oral omeprazole is a standard treatment for gastric ulcers in horses, an intravenous formulation is no longer commercially available in some areas. For horses unable to absorb orally administered omeprazole, intravenous esomeprazole, the s-enantiomer of omeprazole may be an option, but the pharmacokinetics of this drug in horses are currently unknown. Six healthy adult mares were administered a 0.5 mg/kg dose of esomeprazole intravenously and orally in a randomized crossover fashion. After administration, nineteen blood samples were taken over 24 hours and repeated with the opposite treatment after a washout period. Samples were analyzed via HPLC for esomeprazole concentrations and time vs concentration data was modelled with standard industry software. The C0, T1/2, and AUC of IV administered esomeprazole was 2030 ng/mL, 24 min, and 660 ng/ml×hr respectively. The Cmax, T1/2, AUC, and F of oral esomeprazole was 104 ng/mL, 40 min, 114 ng/ml×hr and 25%. Clinicians should consider higher oral doses due to low bioavailability, and further research should focus on pharmacodynamic studies evaluating ulcer healing with esomeprazole therapy in horses.