Daptomycin pharmacokinetics in critically ill patients receiving continuous venovenous hemodialysis. Crit Care Med. 2011;39:19-25. [PMID: 20890189 DOI: 10.1097/ccm.0b013e3181fa36fb]

Current use of daptomycin in cardiac surgery and postoperative intensive care

Infections due to multidrug-resistant pathogens have an increasing impact on patients undergoing cardiac surgery. Preoperative infections, such as endocarditis, and postoperative infections, including wound and device infection, influence patient outcomes. Special interest needs to be taken in patients admitted to cardiac surgical intensive care units, as these patients are at high risk for infections, particularly nosocomial pneumonia, catheter-related and wound infections. The increasing numbers of infections due to Gram-positive multidrug-resistant pathogens underline the necessity for newer antibiotics with bactericidal effects and a more favorable profile of side effects. Daptomycin, a lipopeptide antimicrobial agent with bactericide activity against Gram-positive organisms, has been successfully used in the treatment of complicated infections due to Gram-positive multidrug-resistant pathogens, especially regarding endocarditis, wound infections, device and catheter-related infections in intensive care units. In this review, the authors will summarize therapeutic potential of daptomycin in cardiac surgery and postoperative intensive care.

Population pharmacokinetics of daptomycin in patients affected by severe Gram-positive infections

A population pharmacokinetic analysis of daptomycin was performed based on therapeutic drug monitoring (TDM) data from 58 patients receiving doses of 4-12 mg/kg for the treatment of severe Gram-positive infections. At a daily dose of 8 mg/kg, daptomycin plasma concentrations (mean ± S.D.) were 76.9 ± 9.8 mg/L at the end of infusion and 52.7 ± 15.4 mg/L and 11.4 ± 5.4 mg/L at 0.5 h and 23 h after drug administration, respectively. The final model was a one-compartmental model with first-order elimination, with estimated clearance (CL) of 0.80 ± 0.14 L/h and a volume of distribution (V(d)) of 0.19 ± 0.05 L/kg. Creatinine clearance (CL(Cr)) was identified as having a significant influence on daptomycin CL, and a decrease in CL(Cr) of 30 mL/min from the median value (80 mL/min) was associated with a reduction of daptomycin CL from 0.80 L/h to 0.73 L/h. These results confirm that the presence of severe infection may be associated with an altered disposition of daptomycin, with an increased Vd. MICs were available in 41 patients and results showed that 38 and 31 subjects achieved AUC/MIC values associated with bacteriostatic (>400) and bactericidal effects (>800), respectively. Of note, 31 of these 41 subjects experienced a clinical improvement or were cured. Although daptomycin pharmacokinetics may be influenced by infections, effective AUC/MIC values were achieved in the majority of patients. The present model may be applied in clinical settings for a TDM routine on the basis of a sparse blood sampling protocol.

Pharmacokinetics of oseltamivir and oseltamivir carboxylate in critically ill patients receiving continuous venovenous hemodialysis and/or extracorporeal membrane oxygenation

STUDY OBJECTIVE

To investigate oseltamivir and oseltamivir carboxylate pharmacokinetics in critically ill patients who were receiving continuous venovenous hemodialysis (CVVHD) and/or extracorporeal membrane oxygenation (ECMO).

DESIGN

Prospective, open-label, pharmacokinetic study.

SETTING

Intensive care units of an academic medical center.

PATIENTS

Thirteen critically ill patients aged 13 years or older with suspected or confirmed H1N1 influenza who had a prescription for oseltamivir and were concurrently receiving CVVHD and/or ECMO between October 2009 and January 2010.

INTERVENTION

Oseltamivir 150 mg was administered nasogastrically or nasoenterically every 12 hours. Blood samples were collected at baseline and at 1, 2, 4, 6, 8, 10, and 12 hours after administration of the fourth oseltamivir dose or subsequent doses. In patients receiving CVVHD, effluent also was collected at the same time points. Urine was collected throughout the 12-hour dosing interval.

MEASUREMENTS AND MAIN RESULTS

Eight patients received CVVHD only, four patients received both CVVHD and ECMO, and one patient received ECMO only. Pharmacokinetic parameters for the patient who received only ECMO were not reported. The median maximum plasma concentration and area under the plasma concentration-time curve for the 12-hour dosing interval (AUC(0-12) ) for the remaining 12 patients were 83.4 ng/ml and 216 ng•hour/ml, respectively, for oseltamivir and 2000 ng/ml and 21,500 ng•hour/ml, respectively, for oseltamivir carboxylate. Mean clearance due to CVVHD was 33.8 ml/minute for oseltamivir and 50.2 ml/minute for oseltamivir carboxylate. For patients who received ECMO, no substantial differences between pre- and post-ECMO oxygenator plasma concentrations were found for oseltamivir or oseltamivir carboxylate.

CONCLUSION

Although the optimal pharmacokinetic-pharmacodynamic targets for oseltamivir carboxylate remain unclear, in the patients receiving CVVHD with or without ECMO, a regimen of oseltamivir 150 mg every 12 hours yielded a median oseltamivir carboxylate AUC(0-12) considerably higher than would be expected in non-critically ill patients receiving the same dosage regimen.

Vancomycin clearance in high-volume venovenous hemofiltration

OBJECTIVE

To report the pharmacokinetic and pharmacodynamic properties of vancomycin in 4 patients undergoing high-volume continuous venovenous hemofiltration (CVVH).

CASE SUMMARY

Data from 4 patients prescribed high-volume CVVH for acute renal failure treated with vancomycin were analyzed. Vancomycin plasma concentrations were measured 4 and 24 hours after the end of a 1-hour vancomycin infusion. The mean therapy fluid rate on initiation of vancomycin was 56.2 mL/kg/h (range 48.0-65.5). The mean loading dose of vancomycin was 18.3 mg/kg (range 14.7-19.7). Median vancomycin concentration 4 hours after the dose was 18.1 mg/L (range 13.1-30.0). At 24 hours after the dose, only 1 patient had a detectable vancomycin concentration (5.2 mg/L).

DISCUSSION

There was a large variability in the clearance of vancomycin in this patient population. Current strategies for dosing vancomycin may lead to subtherapeutic trough concentrations. Vancomycin dosing in this patient population should be based on a detailed assessment of the CVVH prescription, vancomycin concentrations, and clinical needs and response.

CONCLUSIONS

An initial vancomycin dose of 20-25 mg/kg with frequent monitoring and adjustment is recommended for patients receiving high-volume CVVH.

The pharmacokinetics of oseltamivir and oseltamivir carboxylate in a critically ill pediatric patient receiving extracorporeal membrane oxygenation and continuous venovenous hemodialysis

This report details the pharmacokinetics of oseltamivir and oseltamivir carboxylate following administration of high-dose oseltamivir in a critically ill child receiving extracorporeal membrane oxygenation (ECMO) and continuous venovenous hemodialysis (CVVHD). A 6-year-old critically ill male patient suffering from a presumed viral illness was transferred to our institution's pediatric intensive care unit from an outside hospital after developing respiratory failure and cardiomegaly. ECMO and oseltamivir therapy were initiated upon admission, and CVVHD was started on hospital day 3. Pharmacokinetic sampling occurred at an oseltamivir dose of approximately 4 mg/kg on hospital day 6. The patient's oseltamivir and oseltamivir carboxylate area under the plasma concentration time curves for the 12-hour dosing interval (AUC(0-12)) were 30.5 and 905 ng/mLhr, respectively. Drug clearance by CVVHD was 31.6 mL/min for oseltamivir and 26.9 mL/min for oseltamivir carboxylate. Pre- and postoxygenator oseltamivir and oseltamivir carboxylate plasma concentrations did not differ substantially. The patient's oseltamivir carboxylate plasma concentrations remained well above the reported mean 50% inhibitory concentration for 2009 pandemic H1N1 virus. However, despite receiving twice the standard dose of oseltamivir, the oseltamivir carboxylate AUC(0-12) in our patient was less than that reported in noncritically ill pediatric subjects. The reduced oseltamivir carboxylate AUC(0-12) found in our patient was most likely due to decreased drug absorption.

Experience with daptomycin daily dosing in ICU patients undergoing continuous renal replacement therapy

PURPOSE

For critically ill patients undergoing continuous renal replacement therapy (CRRT), daptomycin dosing recommendations are scarce. We, therefore, retrospectively assessed routinely measured daptomycin plasma concentrations, daptomycin dose administered and microbiological data in 11 critically ill patients with Gram-positive infections that had received daptomycin once daily.

METHODS

The retrospective analysis included critically ill patients treated at the intensive care unit (ICU) who had daptomycin plasma concentrations measured.

RESULTS

Daptomycin dose ranged from 3 to 8 mg/kg/q24 h in patients undergoing CRRT (n = 7) and 6 to 10 mg/kg/q24 h in patients without CRRT (n = 4). Peak and trough concentrations showed a high intra- and inter-patient variability in both groups, independent of the dosage per kg body weight. No drug accumulation was detected in CRRT patients with once-daily daptomycin dosing. Causative pathogens were Enterococcus faecium (n = 6), coagulase-negative Staphylococcus (n = 2), Staphylococcus aureus (n = 2) and unknown in one patient. Microbiological eradication was successful in 8 of 11 patients. Two of three patients with unsuccessful microbiological eradication and fatal outcome had an Enterococcus faecium infection.

CONCLUSION

In critically ill patients undergoing CRRT, daptomycin exposure with once-daily dosing was similar to ICU patients with normal renal function, but lower compared to healthy volunteers. Our data suggest that daptomycin once-daily dosing is appropriate in patients undergoing CRRT.

Use of an in vitro model of renal replacement therapy systems to estimate extracorporeal drug removal

The use of in vitro modeling to predict in vivo drug and solute clearance during renal replacement therapy has evolved to reflect the different dialytic therapies available in clinical practice. This area of renal replacement therapy research is representative of translational research that demonstrates a correlation from bench to bedside where results generated in the laboratory can assist with clinical decisions in the absence of in vivo studies. This review describes in vitro renal replacement therapy models and compares the findings of several in vitro and in vivo studies.

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.

[Antibiotic dose adjustment in the treatment of MRSA infections in patients with acute renal failure undergoing continuous renal replacement therapies]

Acute renal failure is frequent in critically ill patients. In those patients who need renal replacement therapy, continuous techniques are an alternative to intermittent haemodialysis. Critically ill patients often have an infection, which can lead to sepsis and renal failure. An early and adequate antibiotic treatment at correct dosage is extremely important. Methicillin resistant Staphylococcus aureus (MRSA) is a frequent nosocomial pathogen that causes a high rate of morbidity and mortality in critically ill patients. Many antibiotics are easily removed by continuous renal replacement therapies (CRRT) leading to a high risk of under dosing and therapeutic failure or resistance breakthrough. The objective of this review is to assess the clinical evidence on the pharmacokinetics and dosage recommendations of the main antibiotic groups used in MRSA treatment in patients treated with CRRT.

Antibiotic dosing in critically ill patients with acute kidney injury

A common cause of acute kidney injury (AKI) is sepsis, which makes appropriate dosing of antibiotics in these patients essential. Drug dosing in critically ill patients with AKI, however, can be complicated. Critical illness and AKI can both substantially alter pharmacokinetic parameters as compared with healthy individuals or patients with end-stage renal disease. Furthermore, drug pharmacokinetic parameters are highly variable within the critically ill population. The volume of distribution of hydrophilic agents can increase as a result of fluid overload and decreased binding of the drug to serum proteins, and antibiotic loading doses must be adjusted upwards to account for these changes. Although renal elimination of drugs is decreased in patients with AKI, residual renal function in conjunction with renal replacement therapies (RRTs) result in enhanced drug clearance, and maintenance doses must reflect this situation. Antibiotic dosing decisions should be individualized to take into account patient-related, RRT-related, and drug-related factors. Efforts must also be made to optimize the attainment of antibiotic pharmacodynamic goals in this population.