Drug-protein binding during continuous ambulatory peritoneal dialysis

This study of drug-protein binding in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) measured the serum and dialysate binding of cefamandole - an acidic, cephalosporin antibiotic. Ten CAPD patients, five with and five without peritonitis received a 1.0 g intraperitoneal dose of cefamandole; serum and dialysate was sampled at 4, 10, and 24 h after drug administration. Binding also was studied in serum obtained from five chronic hemodialysis patients and five normal volunteers. Equilibrium dialysis was used to determine protein binding and high performance liquid chromatography to measure cefamandole. Mean fraction unbound (f(u)) serum values for CAPD patients were 0.35 ± 0.04 (noninfected) and 0.37 ± 0.14 (peritonitis). In comparison, the f(u) values in hemodialysis patients were 0.41 ± 0.19 and 0.15 ± 0.02 in normal volunteers. Greater than 90% of cefamandole in dialysate was unbound suggesting that antibiotics, which cross the peritoneal membrane, are present in the free, microbiologically active form.