Cimetidine is unlikely to increase formation of intragastric N-nitroso-compounds in patients taking a normal diet.

Studies in fasting subjects have suggested that cimetidine therapy might lead to nocturnal hypochlorhydria, allowing bacterial overgrowth and the production of intragastric carcinogens. This hypothesis was investigated in normal subjects taking full-dose and maintenance cimetidine with food. Nocturnal hypochlorhydria wa rarely found and the incidence of bacterial overgrowth was correspondingly low; gastric-juice nitrite concentrations were rarely raised. These findings suggest that long term treatment with cimetidine is unlikely to promote gastric cancer as a result of bacterial metabolic activity.