Acute psychoses associated with the use of ciprofloxacin and trimethoprim-sulfamethoxazole.

Although adverse drug reactions are a well-recognized cause of mental status changes in the elderly, antimicrobials are rarely implicated. Three patients with serious organic brain disease developed paranoid psychosis after therapy with trimethoprim-sulfamethoxazole or ciprofloxacin was begun. One of the patients was accidently rechallenged and again developed a psychotic reaction. The acute psychoses did not improve with moderate doses of major tranquilizers but resolved completely with drug discontinuation.