Adverse reactions to co-trimoxazole in hospitalized medical patients.

Of 29,524 hospitalized medical patients monitored in a drug surveillance program, 649 (2.2%) received the fixed dose combination of trimethoprim-sulfamethoxazole, co-trimoxazole. Adverse effects of this drug occurred in 8% of recipients, the most frequent being skin rashes which occurred in 23 patients (3.5%) and upper gastrointestinal upsets which occurred in 22 (3.4%). Reactions frequently occurred within 72 hours of starting the drug and promptly resolved on stopping it. No patient experienced severe or life-threatening adverse effects. Adverse effects were unrelated to age, weight, duration of hospitalization or presenting blood urea nitrogen concentration, but were significantly commoner in female recipients.