Trimethoprim/sulfamethoxazole and renal function in transplant patients

Twenty-two patients with functioning renal allografts took part in a double-blind crossover trial during which placebo, sulfamethoxazole, and trimethoprim/sulfamethoxazole were given for periods of 14 days. The patients were divided into 2 groups. The first group consisting of 12 patients had serum creatinine levels less than 0.18 mmol/L and the second group of 10 patients had serum creatinine levels between 0.18 mmol/L and 0.35 mmol/L. Renal function at the end of each period was assessed by clearance of inulin (CIn), p-aminohippurate (CPAH) and endogenous creatinine (CCr). The second group also had a pitressin concentration test as a measure of distal tubule function. There was no change in inulin or creatinine clearance or in maximum concentration after pitressin in any of the patients in any of the phases. In the first group there was an increase in PAH clearance during the sulfonamide and trimethroprim/sulfamethoxazole phases. This change was not seen in the second group of patients with significantly impaired renal function.