Effect of cimetidine on canine gastric mucosal pH and blood flow.

The effects of cimetidine inhibition of acid secretion on gastric mucosal blood flow and the intramural pH of gastric mucosa were assessed in a canine model ex vivo. Intravenous infusion of histamine at 1.0 microgram/kg per minute resulted in brisk acid secretion, which was associated with an increase in total gastric and mucosal blood flow and the intramural pH of gastric mucosa. The increased blood flow and mucosal alkalinity may be compensatory mechanisms of the stomach to enhance its tolerance of luminal acid. Cimetidine inhibition of acid secretion was associated with a reduction in mucosal alkalinity and total gastric and mucosal blood flow. These adverse effects of cimetidine on blood flow and mucosal pH, two important factors in the stomach's self-defense against acid injury, may explain the inefficacy of cimetidine in the prevention of stress ulcers.