Co-trimoxazole (sulphamethoxazole plus trimethoprim) peritoneal barrier transfer pharmacokinetics

The pharmacokinetics of co-trimoxazole (sulphamethoxazole plus trimethoprim) were studied in end-stage renal disease in patients undergoing treatment with continuous ambulatory peritoneal dialysis (CAPD) and free of peritonitis. Plasma and dialysate concentrations were monitored for 1 exchange after administration of a single oral or intraperitoneal dose of co-trimoxazole, and were fitted by a pharmacokinetic model that took into account the equilibrium nature of CAPD by including return from the peritoneum in oral studies and from the plasma in intraperitoneal studies. Clearances were calculated and compared by analysis of variance. There was a significant effect of direction of flow (p less than 0.01), plasma-peritoneal clearances being larger than peritoneal-plasma clearances for both drugs. In addition, there was a significant difference (p less than 0.0001) between sulphamethoxazole clearances and trimethoprim clearances, with the latter being greater in both directions.