Neurological and psychiatric side effects of cimetidine are reviewed in 47 cases from the literature, and 3 further cases are described. Confusion, psychomotor restlessness, hallucinations and disorientation, stupor and coma were the main features; some had convulsions and a few exhibited focal neurological deficits or neuropathies. The signs appeared within 2 days in almost half of the patients, and remitted in most within 2-3 days. Predisposing factors, of which more than one may be present, are advanced age, hepatic or renal dysfunction, or severe underlying disease. The 3 cases described were all old, one had cirrhosis with bleeding oesophageal varices, and one had renal failure with nephrotic syndrome and amyloidosis.
In view of the increasingly wide use of cimetidine, conditions in which there is decreased metabolic breakdown, or excretion, or predisposition to increased brain levels should prompt careful follow-up, and possibly a lower dosage regimen, especially in elderly patients.