Daptomycin elimination by CVVH in vitro: evaluation of factors influencing sieving and membrane adsorption

Antibiotics Removal by Continuous Venovenous Hemofiltration with a Novel Asymmetric Triacetate Membrane Hemofilter: An in vitro Study

INTRODUCTION

Continuous renal replacement therapies (CRRTs) are essential in the treatment of critically ill patients with acute kidney injury and are also discussed as a supporting sepsis therapy. CRRT can affect antibiotics plasma concentrations.

OBJECTIVE

The effect of continuous venovenous hemofiltration (CVVH) with an asymmetric triacetate (ATA) membrane hemofilter on concentrations of antibiotics with low (meropenem), medium (vancomycin), and high (daptomycin) protein binding (PB) was investigated.

METHODS

1 L human whole blood supplemented with antibiotics was recirculated and filtrated for 6 h in vitro. Clearances and sieving coefficients (SC) were determined from antibiotics concentrations measured at filter inlet, outlet, and filtrate side. Reservoir concentration data were fitted using a first-order kinetic model.

RESULTS

Meropenem and vancomycin concentrations decreased to 5-10% of the initial plasma level, while only 50% of daptomycin were removed. Clearances and SCs were (10.8 [10.8-17.4] mL/min, SC = 0.72 [0.72-1.16]) for meropenem, (13.4 [12.3-13.7] mL/min, 0.89 [0.82-0.92]) for vancomycin, and (2.1 [1.8-2.1] mL/min, 0.14 [0.12-0.14]) for daptomycin. Removal by adsorption was negligible.

CONCLUSIONS

The clearances and SCs presented are comparable with findings of other authors. Meropenem and vancomycin, which exhibit low and medium PB, respectively, were strongly removed, while considerably less daptomycin was removed because of its high PB. Our results suggest that in clinical use of the tested antibiotics during CRRT with the ATA hemofilter, the same factors have to be considered for determining the dosing strategy as with filters with other commonly applied membrane materials.

Can we use an ex vivo continuous hemofiltration model to describe the adsorption and elimination of meropenem and piperacillin?

OBJECTIVES

To determine the adsorption and elimination characteristics of meropenem and piperacillin during simulated continuous renal replacement therapy (CRRT), and to compare the observed data from this ex vivo study with previous data from clinical studies.

METHOD

This was an experimental study utilizing a modified CRRT circuit and polysulfone membrane (1.2 m2), circulated with a blood-crystalloid mixture. Adsorption onto the CRRT circuit was tested over a 4-h period, and clearance was assessed separately using variable continuous hemofiltration settings.

RESULTS

A rapid 9% reduction in circulating meropenem and piperacillin concentrations was observed at approximately 0.5 and 1.0 h for each antibiotic, respectively. The post-dilution setting was associated with a significantly higher sieving coefficient (Sc) and filter clearance (CLfilter) (mean ± SD) (Sc 1.14 ± 0.10 versus 1.06 ± 0.04; CLfilter 19.05 ± 1.63 versus 17.59 ± 0.62 ml/min, P values < 0.05) for meropenem. No significant differences were observed for piperacillin pharmacokinetics. Clinically comparable Sc data were observed between data obtained from the ex vivo study and data from previous clinical studies, for both antibiotics.

CONCLUSIONS

Meropenem and piperacillin appear to be rapidly adsorbed into the CRRT circuit, and the delivery site of fluid replacement significantly influences meropenem pharmacokinetics. However, these findings are likely to be clinically insignificant and not affect dosing requirements. This ex vivo method could be a surrogate for future clinical pharmacokinetic studies of CRRT. Further research is required to explore the applicability of the ex vivo method to further characterize antibiotic pharmacokinetics during CRRT.

Treatment with echinocandins during continuous renal replacement therapy

Echinocandins are indicated as first-line treatment for invasive candidiasis in moderate to severe illness. As sepsis is the main cause of acute kidney injury, the combination of echinocandin treatment and continuous renal replacement therapy (CRRT) is common. Optimizing antibiotic dosage in critically ill patients receiving CRRT is challenging. The pharmacokinetics of echinocandins have been studied under various clinical conditions; however, data for CRRT patients are scarce. Classically, drugs like echinocandins with high protein binding and predominantly non-renal elimination are not removed by CRRT, indicating that no dosage adjustment is required. However, recent studies report different proportions of echinocandins lost by filter adsorption. Nevertheless, the clinical significance of these findings remains unclear.

Multiple-dose pharmacokinetics of daptomycin during continuous venovenous haemodiafiltration

OBJECTIVES

Daptomycin is bactericidal against Gram-positive bacteria, with peak-dependent effect but trough-dependent toxicity. This study was performed to develop dosing recommendations in continuous venovenous haemodiafiltration (CVVHDF).

PATIENTS AND METHODS

Nine critically ill patients in intensive care units of the Medical University Hospital of Vienna, requiring CVVHDF due to acute renal failure and antimicrobial treatment, were included. Blood and effluent samples were collected over 72 h to determine daptomycin concentrations by HPLC. Pharmacokinetic parameters were based on 10 sampling timepoints during the first 24 h, and peak and trough samples thereafter. An open two-compartment model was fitted to each subject's plasma concentration-time data. Simulations of serum concentration-time profiles after different doses and intervals were performed using ADAPT 5.

RESULTS

Peak plasma concentrations with 6 mg/kg daptomycin were 62.2 ± 16.2, 66.1 ± 17.3 and 78.5 ± 22.1 mg/L on days 1, 2 and 3, respectively. The total clearance was 6.1 ± 4.9 mL/min, and the elimination half-life was 17.8 ± 9.7 h. Daptomycin was filtrated and could therefore be measured in the effluent. Protein binding was lower than that seen in healthy volunteers. The unbound fraction was 16 ± 4.5%. All subjects maintained trough serum concentrations above 4 mg/L, at which relevant pathogens are considered daptomycin-susceptible. Accumulation resulted when daptomycin was given every 24 h. Simulation of 8 mg/kg daptomycin given every 48 h resulted in adequate levels without accumulation.

CONCLUSIONS

We recommend 8 mg/kg daptomycin every 48 h in patients on CVVHDF and therapeutic drug monitoring, if possible.

Recent Publications on Medications and Pharmacy

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