Delirium following a Switch from Cimetidine to Famotidine

OBJECTIVE:To describe a patient who developed delirium when switched from cimetidine to famotidine.CASE SUMMARY:An 84-year-old Taiwanese woman was hospitalized for tarry stools. Her past medical history revealed only a decrease in renal function. She tolerated both oral and intravenous cimetidine therapy with a daily dose of 400–900 mg intermittently for 20 years. On hospital days 1–3, cimetidine 300 mg was injected intravenously every eight hours without difficulty. Considering the possible existence of a cimetidine-resistant bleeding ulcer, famotidine 20 mg was given twice daily orally on hospital days 4–7 and then injected intravenously. Six days after being switched from cimetidine to famotidine, the woman's mental status deteriorated. A series of clinical tests revealed no apparent causative factors. Famotidine was then suspected as a probable cause of her delirium. Discontinuation of the drug resulted in rapid resolution of the patient's delirious status.DISCUSSION:Famotidine crosses the blood—brain...