Pharmacokinetics of esomeprazole following intravenous and oral administration in healthy dogs

Investigation into the pharmacokinetic profile of esomeprazole was conducted using eight healthy dogs after intravenous (IV) and oral (po) administration in a two-part randomized crossover study. The dogs were fasted for a minimum of 12 hours and then received esomeprazole either intravenously (dose range 0.93–1.48 mg/kg) or orally using an enteric-coated formulation (dose range 0.95–1.50 mg/kg). After a 1-week washout period, the dogs received an alternative treatment. Serial blood samples were collected at predetermined time points, and plasma esomeprazole concentrations were determined by using ultra-high-performance liquid chromatography–mass spectrometry. Noncompartmental pharmacokinetic analyses were performed. Then, the area under the plasma concentration/time curve (AUC) and maximal plasma concentration (C_max) values were normalized to a 1.0 mg/kg dose of esomeprazole, that is, AUC/dose. Median (range) dose-normalized peak plasma concentration (C_max) values for the IV and po formulations were 4.06 µg/mL (2.47–4.57 µg/mL) and 1.04 µg/mL (0.31–1.91 µg/mL), respectively. The median (range) time-to-peak concentration (T_max) for the po formulation was 105 minutes (45–360 minutes). Median (range) plasma terminal half-life (t_½) was 45.56 minutes (39.43–64.20 minutes) for the IV formulation and 63.97 minutes (44.02–109.94 minutes) for the enteric-coated po formulation. The median (range) po bioavailability was 63.33% (32.26%–79.77%). Clinically, both po and IV formulations were well tolerated with minimal side effects observed.