Mental status, the intensive care unit, and cimetidine.

A blinded, prospective study of the association between cimetidine treatment and altered mental status (MS) was evaluated in 217 surgical intensive care patients stratified by the degree of renal or hepatic dysfunction or both. The cimetidine and noncimetidine groups did not differ in blood chemistries, physiologic-metabolic data, or concurrent medications. There was a correlation between treatment with cimetidine and changes in MS (p less than 0.0001). The MS changes with cimetidine ranged from 33% for neither hepatic nor renal dysfunction to 80% for both renal and liver impairment. The magnitude of MS change was influenced by disease and serum concentration, with patients with both renal and liver disease having the greatest MS change at the highest serum concentrations. The type of MS change was also disease specific. All MS change cleared within 24 to 36 hours of stopping the drug. It appears that both dosage and underlying disease state are important factors determining the nature and severity of cimetidine-associated mental status changes.