Pharmacokinetics and pharmacodynamics of once-daily arbekacin during continuous venovenous hemodiafiltration in critically ill patients.
ABSTRACT This study examined the pharmacokinetics of arbekacin during continuous venovenous hemodiafiltration (CVVHDF) and assessed the pharmacodynamics to consider arbekacin dosage adaptation in CVVHDF. Arbekacin was administered by 0.5-h infusion once daily, using a polymethyl methacrylate membrane hemofilter, to three critically ill patients undergoing CVVHDF; the flow rates were 0.8 l/h for the filtrate and 0.6 l/h for the dialysate. The drug concentrations in plasma and in the filtrate-dialysate were determined using a fluorescence polarization immunoassay and analyzed pharmacokinetically. The average sieving coefficient of arbekacin was 0.739 and the average drug clearance by CVVHDF was 1.03 l/h. A pharmacokinetic model with three compartments (1, central; 2, peripheral; 3, filtrate-dialysate side hemofilter) accurately reflected the concentration-time data for both plasma and filtrate-dialysate. The pharmacokinetic model assessed the pharmacodynamic profile of arbekacin once-daily regimens (0.5-h infusions) at filtrate-dialysate flow rates of 1.4 and 2.8 l/h, and demonstrated that only the 150-mg and 200-mg regimens achieved an effective target range for C(max) (9-20 microg/ml), suggesting that empirical dosages lower than the usual 150-200 mg should be avoided in patients undergoing CVVHDF. The minimum regimens needed to achieve an effective pharmacodynamic target for the free C(max)/MIC ratio (>8) were 75 mg for an MIC of 0.5 microg/ml, 200 mg for an MIC of 2 microg/ml, and 400 mg for an MIC of 4 microg/ml. These results will help us to better understand the pharmacokinetics of arbekacin during CVVHDF, while also helping in the selection of the appropriate arbekacin regimens, based on a pharmacodynamic assessment, for patients receiving this renal replacement therapy.
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ABSTRACT: To outline the concepts involved in optimizing antibacterial dosing in critically ill patients with acute renal failure undergoing continuous renal replacement therapy (CRRT), provide a strategy for optimizing dosing, and summarize the data required to implement the strategy. MEDLINE search from February 1986 to 2008. Optimal dosing of antibacterials is dependent on achieving pharmacokinetic targets associated with maximal killing of bacteria and improved outcomes. The initial dose is dependent on the volume of distribution. Maintenance doses are dependent on clearance. Both should be adjusted according to the pharmacokinetic target associated with optimal bacterial killing, when known. The volume of distribution of some antibacterials is altered by critical illness or acute renal failure or both. Clearance by CRRT is dependent on the dose and mode of CRRT and the sieving or saturation coefficient of the drug. Both sieving and saturation coefficient are related to the plasma protein binding and thus may be altered in renal failure. Appropriate dose calculation requires knowledge of the pharmacokinetic target and the usual minimum inhibitory concentration of the suspected organism in the patient's locality (or if unavailable, the break point for the organism), published pharmacokinetic data (volume of distribution, non-CRRT clearance) on critically ill patients receiving CRRT (which may differ substantially from noncritically ill patients or those without renal failure), the sieving or saturation coefficient of the relevant drug in critically ill patients, the dose and mode of CRRT being used, and the actual dose of CRRT that is delivered. This large number of variables results in considerable inter- and intrapatient heterogeneity in dose requirements. This article provides basic principles and relevant data to guide the clinician in prescribing individualized dosing regimes.Critical care medicine 08/2009; 37(7):2268-82. · 6.37 Impact Factor