Urolithiasis as a hazard of sulfonamide therapy.

We identified 40 patients (25 men and 15 women) who developed calculi composed totally or partially of sulfonamides (acetylsulfamethoxazole, sulfadiazine, and acetylsulfisoxazole) between 1980 and 1987. The incidence of sulfonamide stones is less than 1% of stones. Patient characteristics were determined from questionnaires sent to the patients and attending physicians. The majority of patients developed symptoms 1 to 4 weeks after beginning sulfonamide therapy. The bladder was the most common stone location. Obstruction of the urinary system by the acetyl derivatives of the drug is the most serious consequence of sulfonamide therapy. Early recognition of drug-related stones is essential to protect patients from recurrences, reduce the risk of renal complications, and avoid continuing ineffective therapeutic regimens.