Pharmacokinetics of once-daily IP gentamicin in CAPD patients

Objective:This study aimed to investigate the pharmacokinetic characteristics of once-daily intraperitoneal (IF) gentamicin in continuous ambulatory peritoneal dialysis (CAPD) patients. Design: Prospective, nonrandomized, open study. Setting: CAPD outpatient clinic in a teaching hospital. Patients: Ten volunteer CAPD patients without peritonitis. Interventions: Each patient received a single IP dose of 0.6 mg/kg of gentamicin. Blood and dialysate samples were collected at 0, 0.5, 1, 2, 3, 6 (end of first dwell), and 24 hours after the administration of IP gentamicin. Any urine produced over the 24-hour study period was also collected. The dialysate concentration/time data were fitted to a monoexponential curve for all patients. Results: The bioavailability was 56+/-11% over a six-hour dwell. The mean serum elimination half-life (t(1/2)) was 35.8 hours. The volume of distribution was 0.23+/-0.08 L/kg. Equilibration of gentamicin across the peritoneal membrane was rapid, with a t(1/2) equilibration of 4.5 hours. The peritoneal clearance was 5.74+/-1.5 mL/min. Patients with residual renal function had significantly higher systemic gentamicin clearances (7.36+/-1.46 mL/min) than those of anuric patients (4.76+/-1.08 mL/min, p < 0.024). Conclusion: Currently recommended doses of once-daily IP gentamicin for the treatment of peritonitis may not produce the desired therapeutic serum and dialysate concentrations over 24 hours for effective treatment of peritonitis.