Twice-daily cimetidine does not increase gastric bacterial flora

Thirty patients with peptic ulcer (20 duodenal, 10 gastric) underwent glucose-hydrogen (H2) breath tests before and after 6 weeks treatment with cimetidine, 400 mg twice daily. For the group as a whole, basal breath H2 and integrated H2 output over a 2.5 hr test period was unchanged by cimetidine treatment. We conclude that there was no evidence of significant gastric bacterial colonization following twice daily cimetidine treatment.