The effects of dose and diet on the pharmacokinetics of omeprazole in the horse.

Abstract

This study aimed to investigate the effect of diet and dose on the pharmacokinetics of omeprazole in the horse. Six horses received two doses (1 and 4mg/kg) of omeprazole orally once daily for 5days. Each dose was evaluated during feeding either a high-grain/low-fibre (HG/LF) diet or an adlibitum hay (HAY) diet in a four-way crossover design. Plasma samples were collected for pharmacokinetic analysis on days 1 and 5. Plasma omeprazole concentrations were determined by ultra-high pressure liquid chromatography-mass spectrometry. In horses being fed the HG/LF diet, on day 1, the area under the curve (AUC) and maximal plasma concentration (Cmax ) were higher on the 4mg/kg dose than on the 1mg/kg dose. The AUC was higher on day 5 compared to day 1 with the 4mg/kg dose on the HG/LF diet. On days 1 and 5, the AUC and Cmax were higher in horses being fed the HG/LF diet and receiving the 4mg/kg dose than in horses being fed the HAY diet and receiving the 1mg/kg dose. These findings suggest that both dose and diet may affect pharmacokinetic variables of omeprazole in the horse.