Fever after cimetidine and ranitidine.

A 54-year-old bed-bound multiple sclerosis patient experienced fever, mental confusion, and marginal serum creatinine elevations after receiving cimetidine and subsequently ranitidine therapy. Fever and mental confusion recurred following a planned ranitidine challenge. We do not know whether a direct effect on the thermoregulatory center or a hypersensitivity reaction to the drugs was the mechanism of fever production in this patient.