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Pharmacological particulars
ATC Vet Code: QA02BA01
Pharmacotherapeutic group: H2-receptor antagonists
Pharmacodynamic properties
Cimetidine is an antagonist of the histamine H2-receptors present in the gastric parietal cells. Stimulation of H2-receptors by histamine activates gastric acid secretion. Cimetidine, via its antagonistic properties toward histamine H2-receptors, strongly reduces gastric acid secretion. This may result in the diminution of gastric irritation and subsequent vomiting during chronic gastritis. No accompanying improvement in the inflammatory status of the gastric mucosa was observed in dogs.
Pharmacokinetic particulars
After oral administration of the product at a dose rate of 5 mg/kg body weight to fasted dogs, maximal plasma levels of approximately 2 µg/ml are reached after 1.5 hours post-administration. Bioavailability is about 95%. The extent of absorption of cimetidine in dogs is delayed and reduced by approximately 40 % in the presence of food (Cmax fasted 2.94 mcg/ml, Cmax fed 1.12 mcg/ml, AUC0-∞ fasted 8.23 mcg.h/ml and AUC0-∞ fed 5.43 mcg.h/ml). However, this does not affect the efficacy of treatment
The plasma half-life of cimetidine is approximately 2 hours at a dosage of 5 mg/kg. Cimetidine is rapidly and almost completely excreted into the urine. No drug accumulation occurs after repeated oral treatment at 5 mg/kg three times daily over 30 consecutive days.