OBJECTIVE: This study aimed to investigate the pharmacokinetic characteristics of once-daily intraperitoneal (IP) 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 (t1/2) 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 t1/2 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.

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