Histamine H2 antagonists and the nervous system.

In extensive clinical trials, both cimetidine and ranitidine appeared free of central nervous system side effects. The potential for neurologic complications became apparent only after these drugs had been subjected to the test of general use. The incidence of side effects is generally low, but in the elderly and in patients with renal or hepatic failure, both of these drugs can produce confusional states. Ranitidine may also cause severe headache.