The effects of a new H
2-receptor blocker, ranitidine, given intravenously (for comparison with cimetidine) or orally on gastric and pancreatic secretion have been studied in duodenal ulcer patients. Ranitidine appears to be several times more potent and a longer-acting inhibitor of gastric secretion than cimetidine. This H
2 blocker does not affect pancreatic bicarbonate and enzyme secretion.