Population pharmacokinetics of intra-peritoneal gentamicin and the impact of varying dwell times on pharmacodynamic target attainment in patients with acute peritonitis undergoing peritoneal dialysis

Abstract

While the use of intraperitoneal (i.p.) gentamicin is common in the treatment of peritoneal dialysis (PD)-related infections, the ability of these regimens to attain pharmacodynamic target indices of interest in blood and dialysate has not been widely reported. Pharmacokinetic (PK) data was obtained and analyzed from a multiple-dose PK study of i.p. gentamicin with 24 patients who received the drug at 0.6 mg/kg dose of body weight. The probability of target attainment (PTA) for indices of treatment success (i.p. peak/MIC ratio >10) and toxicity (plasma AUC < 120 mg*h/L) was determined for 0.3 to 1.2 mg/kg i.p. regimens every 24 h for dwell times of 2 to 6 hours and for the duration of 2-week course. In the peritoneum, successful PTA was achieved by all of the simulated regimens up to an MIC of 1 mg/L, and by doses equal to or greater than 0.6 mg/kg up to the MIC of 2 mg/L. At the susceptibility break point of 4 mg/L only the highest dose of 1.2 mg/kg is likely to provide adequate PTA. Probability of achieving exposure below the threshold of 120 mg*h/L in the daily AUC in plasma seems acceptable for all regimens at or below 0.6 mg/kg. Based on the model we developed, a gentamicin dose of 0.6 mg/kg is sufficient to treat organisms with an MIC of ≤2 mg/L without the risk of significant systemic exposure. The 1.2 mg/kg dose necessary to reach the pharmacodynamic target for efficacy at the clinical break point of 4 mg/L is likely to produce early toxic levels of exposure that is expected to be detrimental to the renal system.