Cimetidine as a single oral dose for prophylaxis against Mendelson's syndrome.

Cimetidine, a histamine H2-receptor antagonist which inhibits gastric acid secretion, was administered as a single 400 mg oral dose before anaesthesia to forty-six patients undergoing elective gynaecological surgery. The incidence of gastric residue pH above 2.5 was significantly greater (P less than 0.001) in cimetidine treated patients than in thirty-seven control patients. No patient who received cimetidine between 4 and 6 h prior to anaesthesia had a gastric residue pH less than 2.5. These findings suggest that cimetidine may be effective as a prophylaxis against acid pulmonary aspiration (Mendelson's) syndrome.