Pharmacokinetic studies of cimetidine hydrochloride in adult horses

Publisher Website
Google Scholar
Abstract
Histamine type II (H2) antagonists inhibit gastric acid secretion and are useful in treating gastric and duodenal ulcer disease. To provide some information on the pharmacokinetics of the H2 antagonist cimetidine, adult horses were given 3.3 mg/kg cimetidine intravenously (iv) or 3.3 and 10 mg/kg orally. Plasma cimetidine concentrations after 3.3 mg/kg orally were too low to measure. Following 3.3 mg/kg iv, cimetidine displayed two-compartment characteristics with a t1/2 of 0.083 .+-. 0.039 h and t1/2 of 2.23 .+-. 0.64 h. The total body clearance was 0.443 .+-. 0.160 litre/h/kg and the mean residence time was 2.74 .+-. 1.11 h. This clearance and t1/2 are similar to that in man. The volume of distribution (VSS) and volume of the central compartment (VC) were 1.138 .+-. 0.230 and 0.276 .+-. 0.102 litre/kg, respectively. After a single oral dose of 10 mg/kg as crushed tablets, peak plasma concentration of 1.81 .+-. 0.82 .mu.g/ml occurred at approximately 1.4 h. Oral absorption of cimetidine appeared variable and slow with an extent of absorption of 0.296 .+-. 0.183 and a mean residence time for absorption of 1.99 .+-. 0.79 h. This was less than in man. Based on a desired average steady state plasma concentration of 1.0 .mu.g/ml, 11.0 mg/kg/day iv and 48 mg/kg/day orally can be recommended in adult horses.