Trimethoprim-sulfamethoxazole pharmacokinetics during continuous ambulatory peritoneal dialysis

Eight adult patients without peritonitis maintained on chronic ambulatory peritoneal dialysis (CAPD) were administered a single oral dose of 320 mg trimethoprim (TMP) and 1600 mg sulfamethoxazole (SMX) to characterize the pharmacokinetics of TMP and SMX. Ten blood samples were drawn following the dose. TMP and SMX-active (SMXA) concentrations were quantified in serum and dialysate. The half-life of TMP and SMXA determined by model independent methods were 33.7 +/- 10.5 h (mean +/- SD) and 13.8 +/- 2.2 h respectively. Total body clearance of TMP was 32.8 +/- 10.1 ml/min and SMXA was 21.9 +/- 6.4 ml/min. CAPD clearance of TMP was 2.27 +/- 0.81 ml/min and SMXA was 1.72 +/- 0.93 ml/min. The average peritoneal dialysate concentrations over the 72-hour collection period of TMP and SMXA were 0.9 +/- 0.1 mg/l and 5.3 +/- 0.8 mg/l respectively. A dose of 320 mg TMP and 1600 mg SMX every 48 hours is recommended for CAPD patients with mild to moderate systemic infections.