Linezolid clearance during continuous venovenous hemodiafiltration: a case report

Linezolid dosing in critically ill patients undergoing various modalities of renal replacement therapy: a pooled population pharmacokinetic analysis

The altered pharmacokinetics (PK) of linezolid are pronounced in critically ill patients undergoing different modalities of renal replacement therapy (RRT). This study aimed to provide a pooled population PK analysis of linezolid in patients undergoing RRT, and to evaluate the pharmacodynamic target attainment of linezolid standard dosing (600 mg q12h). In total, 414 pooled linezolid concentration observations from 69 patients undergoing intermittent haemodialysis (IHD), sustained low-efficiency dialysis (SLED) or continuous RRT were used to develop the population PK model. The probability of target attainment (PTA) for the efficacy markers of 85% T>minimum inhibitory concentration (MIC) and area under the concentration-time curve (AUC)/MIC >100 was evaluated, and the risk of toxicity was estimated based on Cmin ≥10 mg/L. Linezolid concentration data were described adequately by a two-compartment model. Renal function and body weight were identified as significant modifiers for endogenous clearance of linezolid. Simulations demonstrated that the PTA of 85% T>MIC and AUC/MIC>100 was unacceptably low (0-58.6%, MIC ≥1 mg/L) in RRT patients with preserved renal function, while desirable 85% T>MIC attainment (≥ 90%, MIC ≤2 mg/L) was achieved in anuric RRT patients. The predicted risk of toxicity was negligible (<1.0%) in patients with preserved renal function (regardless of RRT modality), while the probability of reaching Cmin ≥10 mg/L was high (17.9-20.9%) for the anuric patient population undergoing IHD or SLED. In conclusion, standard linezolid dosing is adequate for anuric RRT patients with MIC ≤2 mg/L.

Correlation of antimicrobial fraction unbound and sieving coefficient in critically ill patients on continuous renal replacement therapy: a systematic review

Background

Fraction unbound has been used as a surrogate for antimicrobial sieving coefficient (SC) to predict extracorporeal clearance in critically ill patients on continuous renal replacement therapy (CRRT), but this is based largely on expert opinion.

Objectives

To examine relationships between package insert-derived fraction unbound (Fu-P), study-specific fraction unbound (Fu-S), and SC in critically ill patients receiving CRRT.

Methods

English-language studies containing patient-specific in vivo pharmacokinetic parameters for antimicrobials in critically ill patients requiring CRRT were included. The primary outcome included correlations between Fu-S, Fu-P, and SC. Secondary outcomes included correlations across protein binding quartiles, serum albumin, and predicted in-hospital mortality, and identification of predictors for SC through multivariable analysis.

Results

Eighty-nine studies including 32 antimicrobials were included for analysis. SC was moderately correlated to Fu-S (R2 = 0.55, P &lt; 0.001) and Fu-P (R2 = 0.41, P &lt; 0.001). SC was best correlated to Fu-S in first (&lt;69%) and fourth (&gt;92%) quartiles of fraction unbound and above median albumin concentrations of 24.5 g/L (R2 = 0.71, P = 0.07). Conversely, correlation was weaker in patients with mortality estimates greater than the median of 55% (R2 = 0.06, P = 0.84). SC and Fu-P were also best correlated in the first quartile of antimicrobial fraction unbound (R2 = 0.66, P &lt; 0.001). Increasing Fu-P, flow rate, membrane surface area, and serum albumin, and decreasing physiologic charge significantly predicted increasing SC.

Conclusions

Fu-S and Fu-P were both reasonably correlated to SC. Caution should be taken when using Fu-S to calculate extracorporeal clearance in antimicrobials with 69%–92% fraction unbound or with &gt;55% estimated in-hospital patient mortality. Fu-P may serve as a rudimentary surrogate for SC when Fu-S is unavailable.

Dosage regimen and toxicity risk assessment of linezolid in sepsis patients

BACKGROUND

Significant alterations in the pharmacokinetic characteristics of linezolid are often seen in sepsis patients. The study aimed to identify a target pharmacokinetics/pharmacodynamics (PK/PD) index of the efficacy of linezolid treatment, and to estimate the optimum dosage regimen of linezolid in sepsis patients.

METHODS

The PK data were modeled using the one-compartment model, which determined the target PK/PD index for successful treatment by logistic regression. The probability of thrombocytopenia was identified by establishing a logistic model. Different dosing regimens were evaluated using Monte Carlo simulation.

RESULTS

Reaching 80% bacterial eradication required an AUC₂₄/MIC of 100, which defined the therapeutic target. The proposed regimen to attain a cumulative fraction of response ≥80% was 800 mg/12 h (safety probability 66.8%) for sepsis patients with normal renal function or mild kidney damage. By contrast, the target cumulative fraction of response was attained with a standard dosing regimen in sepsis patients on continuous renal replacement therapy [600 mg/12 h (safety probability 49.7%)].

CONCLUSIONS

This study identified different dosing strategies to achieve target linezolid PK/PD values according to whether sepsis patients were treated with continuous renal replacement therapy. Due to the high incidence of thrombocytopenia in sepsis patients on continuous renal replacement therapy, therapeutic drug monitoring should be encouraged for optimizing linezolid exposure in sepsis patients.

Pharmacokinetics of linezolid in critically ill patients on continuous renal replacement therapy: Influence of residual renal function on PK/PD target attainment

PURPOSE

To assess the pharmacokinetics of linezolid in septic patients undergoing continuous renal replacement therapy (CRRT) and investigate whether residual renal function affects the probability of attaining the pharmacokinetic/pharmacodynamic (PK/PD) target.

MATERIAL AND METHODS

Prospective study conducted in three Spanish hospitals. Linezolid concentrations were measured in plasma and effluent samples and pharmacokinetic parameters were calculated. The probability of target attainment (PTA) and the cumulative fraction of response (CFR) were calculated considering AUC₂₄/MIC>80 and %T_>MIC > 85% as the PK/PD indexes related to efficacy.

RESULTS

In anuric patients (CrCl<10 mL/min), the contribution of extracorporeal Cl to total Cl was higher (47% vs 16%) than in patients with residual renal function (CrCl≥10 mL/min). For an MIC of 2 mg/L, AUC₂₄/MIC>80 was achieved in >85% of the anuric patients, but in <15% of the patients with residual renal function.

CONCLUSIONS

The standard dose (600 mg q12h) ensures a moderately high probability of treatment success in anuric patients when the infection is due to microorganisms with MIC≤2 mg/L; although higher doses increase the probability of treatment success, the safety is compromised. In patients with residual renal function, the standard dose is insufficient, but 900 mg q8h provide higher probability of treatment success without compromising the safety.

Pharmacokinetics of linezolid during continuous hemodiafiltration: A case report

The pharmacokinetics of linezolid clearance (CL_LZD) during continuous hemodiafiltration (CHDF) has not been comprehensively analyzed. Here, we examined CL_LZD by CHDF in a patient with septic shock and disseminated intravascular coagulation due to methicillin-resistant Staphylococcus aureus. The extraction ratio of LZD by CHDF was 22.6%, and the protein-binding rate was 17.9% ± 7.7%. In addition, it was determined that the calculated total body clearance of LZD was 30.2 mL/min, plasma elimination half-life was 8.66 h, and the CL_LZD by the dialyzer used for CHDF was 23.0 mL/min. From the obtained pharmacokinetics, the CL_LZD of patients continuing CHDF was estimated to be approximately half of the reported CL_LZD for healthy subjects. In addition, the LZD concentration of the sepsis patient who underwent CHDF remained higher than the minimum inhibitory concentration and was similar to the LZD concentrations reported in normal renal function patients. Although further studies are warranted, when LZD is administered to patients treated with CHDF, the present findings suggest that dose regulation is not required.

Effects of continuous renal replacement therapy on linezolid pharmacokinetic/pharmacodynamics: a systematic review

Background

Major alterations in linezolid pharmacokinetic/pharmacodynamic (PK/PD) parameters might be expected in critically ill septic patients with acute kidney injury (AKI) who are undergoing continuous renal replacement therapy (CRRT). The present review is aimed at describing extracorporeal removal of linezolid and the main PK-PD parameter changes observed in critically ill septic patients with AKI, who are on CRRT.

Method

Citations published on PubMed up to January 2016 were systematically reviewed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. All authors assessed the methodological quality of the studies and consensus was used to ensure studies met inclusion criteria. In-vivo studies in adult patients with AKI treated with linezolid and on CRRT were considered eligible for the analysis only if operational settings of the CRRT machine, membrane type, linezolid blood concentrations and main PK-PD parameters were all clearly reported.

Results

Among 68 potentially relevant articles, only 9 were considered eligible for the analysis. Across these, 53 treatments were identified among the 49 patients included (46 treated with high-flux and 3 with high cut-off membranes). Continuous veno-venous hemofiltration (CVVH) was the most frequent treatment performed amongst the studies. The extracorporeal clearance values of linezolid across the different modalities were 1.2–2.3 L/h for CVVH, 0.9–2.2 L/h for hemodiafiltration and 2.3 L/h for hemodialysis, and large variability in PK/PD parameters was reported. The optimal area under the curve/minimum inhibitory concentration (AUC/MIC) ratio was reached for pathogens with an MIC of 4 mg/L in one study only.

Conclusions

Wide variability in linezolid PK/PD parameters has been observed across critically ill septic patients with AKI treated with CRRT. Particular attention should be paid to linezolid therapy in order to avoid antibiotic failure in these patients. Strategies to improve the effectiveness of this antimicrobial therapy (such as routine use of target drug monitoring, increased posology or extended infusion) should be carefully evaluated, both in clinical and research settings.

Linezolid extracorporeal removal during haemodialysis with high cut-off membrane in critically ill patients

Continuous venovenous haemodialysis with high cut-off membrane (HCO-CVVHD) is often used in critically ill septic patients with acute kidney injury (AKI) to sustain renal function and to remove circulating inflammatory mediators. The aim of this study was to analyse the extracorporeal removal of linezolid and related alterations in pharmacokinetic/pharmacodynamic (PK/PD) parameters during HCO-CVVHD. Three critically ill septic patients with AKI, treated with linezolid and HCO-CVVHD, were prospectively observed. To calculate the extracorporeal clearance of linezolid and the PK parameters, effluent, pre-filter and post-filter samples were contemporaneously collected before linezolid infusion, just after 1-h infusion (maximum serum concentration; C(max)), at 3 h and 6 h after dosing, and before the next dose (trough serum concentration; C(min)). Linezolid C(max) and C(min) (pre-filter) ranged from 10.4-23.5 mg/L and from 2.9-10.3 mg/L. The dialysate saturation coefficient was 0.66-0.85 and the extracorporeal clearance with a diffusive dose of 35 m L/kg/h ranged from 2.1-2.5 L/h. Total linezolid clearance was between 1.7 L/h and 6.3 L/h. The total area under the plasma concentration-time curve (AUC0-∞) ranged from 95.1 mgh/L to 352.9 mgh/L, in accordance with the different clinical conditions. AUCfree/MIC ratios were always <85 for an MIC of 4.0 mg/L, and two of three patients did not reach the optimal PK/PD target of ≥85 even when using an MIC of 2.0 mg/L. Although extracorporeal clearance may affect linezolid total clearance, the clinical features of critically ill septic patients appear to be mainly responsible for the high variability of linezolid serum concentrations.

Role of linezolid in the treatment of complicated skin and soft tissue infections

Staphylococcus aureus is the most common cause of complicated skin and soft tissue infections (cSSTIs). Antibiotic choices for these infections continue to evolve. History has seen penicillin progress to antistaphylococcal penicillins and cephalosporins, but these drugs are now giving way to drugs that are effective against methicillin-resistant S. aureus (MRSA). While vancomycin has been the gold standard to treat MRSA infections, newer therapeutic options have been developed over the last 5 years. These include quinupristin-dalfopristin, daptomycin, tigecycline and linezolid, which is the focus for this review. Linezolid is efficacious in the treatment of cSSTIs (including diabetic foot infections) caused by Gram-positive organisms (including MRSA), with a well-defined safety profile and straightforward dosing. It is also approved for nosocomial pneumonia, community-acquired pneumonia and uncomplicated skin and skin structure infections. Linezolid has an oral and parenteral formulation, which are equivalent. The oral formulation has the potential to offer economic benefits as compared with other therapies. Currently, there are only a few new antibiotics in development with MRSA activity. The proper use of all antibiotics, including these newer agents, is increasingly important if we are to slow the evolution of microbial resistance.

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.

Presence and accuracy of drug dosage recommendations for continuous renal replacement therapy in tertiary drug information references

BACKGROUND

Clinicians commonly rely on tertiary drug information references to guide drug dosages for patients who are receiving continuous renal replacement therapy (CRRT). It is unknown whether the dosage recommendations in these frequently used references reflect the most current evidence.

OBJECTIVE

To determine the presence and accuracy of drug dosage recommendations for patients undergoing CRRT in 4 drug information references.

METHODS

Medications commonly prescribed during CRRT were identified from an institutional medication inventory database, and evidence-based dosage recommendations for this setting were developed from the primary and secondary literature. The American Hospital Formulary System-Drug Information (AHFS-DI), Micromedex 2.0 (specifically the DRUGDEX and Martindale databases), and the 5th edition of Drug Prescribing in Renal Failure (DPRF5) were assessed for the presence of drug dosage recommendations in the CRRT setting. The dosage recommendations in these tertiary references were compared with the recommendations derived from the primary and secondary literature to determine concordance.

RESULTS

Evidence-based drug dosage recommendations were developed for 33 medications administered in patients undergoing CRRT. The AHFS-DI provided no dosage recommendations specific to CRRT, whereas the DPRF5 provided recommendations for 27 (82%) of the medications and the Micromedex 2.0 application for 20 (61%) (13 [39%] in the DRUGDEX database and 16 [48%] in the Martindale database, with 9 medications covered by both). The dosage recommendations were in concordance with evidence-based recommendations for 12 (92%) of the 13 medications in the DRUGDEX database, 26 (96%) of the 27 in the DPRF5, and all 16 (100%) of those in the Martindale database.

CONCLUSIONS

One prominent tertiary drug information resource provided no drug dosage recommendations for patients undergoing CRRT. However, 2 of the databases in an Internet-based medical information application and the latest edition of a renal specialty drug information resource provided recommendations for a majority of the medications investigated. Most dosage recommendations were similar to those derived from the primary and secondary literature. The most recent edition of the DPRF is the preferred source of information when prescribing dosage regimens for patients receiving CRRT.

[Study of factors affecting drug extraction during continuous hemofiltration and hemodiafiltration, and the contribution of extraction to systemic clearance]

The aim of this study was to elucidate the factors affecting dialysis clearance and the need for additional doses of drugs during and after continuous hemofiltration (CHF) and hemodiafiltration (CHDF). We performed a literature search of MEDLINE using the terms hemofiltration OR hemodiafiltration AND pharmacokinetics to obtain the clearances of CHF and CHDF in a clinical setting. The relationships between molecular weight, the unbound fraction (fuB), ultrafiltration flow rate (UFR) and dialysis flow rate were analyzed. The need for additional doses of certain drugs was also discussed based on the ratio of dialysis and systemic clearances. The clearance of CHF for 32 reported drugs was significantly correlated with the product of fuB×UFR (r=0.841, p<0.001), and furthermore the plots obtained lay on a line of y=x. The clearance of CHDF also showed good correlation with the product of fuB×UFR (r=0.795, p<0.001), but the plots were higher than the line for y=x, suggesting that additional clearance by dialysis was not negligible. The elimination by both forms of dialysis for drugs excreted mainly via the kidneys, and with a higher fuB, was considerable. The extent of drug clearance by both CHF and CHDF is determined mainly by fuB and UFR. The ratio of dialysis clearance to systemic clearance should be estimated to determine the contribution of CHF and CHDF.

[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.

Pharmacological issues of linezolid: an updated critical review

Linezolid is the first oxazolidinone agent introduced into clinical practice for use against Gram-positive bacteria that are resistant to beta-lactams and glycopeptides, including methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). An optimal antibacterial effect is achieved when plasma drug concentrations are above the minimum inhibitory concentration (MIC) [T>MIC] for the entire length of treatment and the ratio between the area under the plasma concentration-time curve (AUC) and the MIC (AUC/MIC) is greater than 100, as is most commonly obtained with administration of the standard dosage of linezolid 600 mg twice daily. A wide tissue distribution, including the CNS and respiratory tract, nearly linear pharmacokinetics and good tolerability are additional characteristics of linezolid. However, variability in the drug pharmacokinetics associated with clinical conditions (e.g. sepsis, burn injuries, end-stage renal disease, cystic fibrosis), haemodialysis and/or young age may lower the T>MIC and the AUC/MIC ratio, thus impairing both antibacterial activity and prevention of mutants. In most cases, changes in the dosage or in the schedule of administration (e.g. an additional [third] daily dose) may improve the effectiveness of linezolid. It is worth noting that linezolid could affect its own metabolism as a result of protein synthesis inhibition in mitochondria, and this could lead to high plasma concentrations and an increased risk of non-negligible toxicities. The latter may be reported during long-term administration of linezolid or in the presence of some pathological conditions (e.g. renal disease or kidney transplantation) associated with high plasma drug concentrations. Therefore, treatment optimization should be considered a requirement for more effective and tolerable use of the drug, particularly in special populations.

Does haemodialysis significantly affect serum linezolid concentrations in critically ill patients with renal failure? A pilot investigation

BACKGROUND

Previous studies have shown that a single haemodialysis (HD) session removes about one-third of the linezolid dose administered, but it is unknown whether in critically ill patients with renal failure on intermittent HD, this removal adversely affects serum antibiotic concentrations.

METHODS

Five male critically ill patients (mean age 75 years, range 68-82; APACHE II score 26.4, range 23-29; survival 2/5) with sepsis and renal failure on haemodialysis, were administered i.v. linezolid, 600 mg every 12 h. Serum antibiotic levels were measured by high-performance liquid chromatography/mass spectrometry. We classified trough concentrations as 'with HD' when a HD session was performed after linezolid infusion, and 'without HD' otherwise. We also computed population pharmacokinetics while patients were on-dialysis and off-dialysis.

RESULTS

A total of 222 serum linezolid concentrations were available over 36 days of antibiotic therapy, during which patients underwent 31 HD sessions. Trough serum linezolid levels averaged 5.83 mg/l (range 1.48-15.84), exceeding 4.0 mg/l in 68.9% of the samples; however, the trough levels 'with HD' were lower than those 'without HD' (4.68 mg/l [range 1.48-9.07] vs 6.74 mg/l [range 2.04-15.84], P<0.001). Clearance and half-life were 6.0 l/h and 4.0 h, respectively, while patients were on-dialysis, and 4.4 l/h and 7.3 h, respectively, when they were off-dialysis.

CONCLUSIONS

HD can significantly reduce serum linezolid levels in critically ill patients with renal failure.

Antibiotic Dosing in Critically Ill Adult Patients Receiving Continuous Renal Replacement Therapy

Continuous renal replacement therapy (CRRT) is now commonly used as a means of support for critically ill patients with renal failure. No recent comprehensive guidelines exist that provide antibiotic dosing recommendations for adult patients receiving CRRT. Doses used in intermittent hemodialysis cannot be directly applied to these patients, and antibiotic pharmacokinetics are different than those in patients with normal renal function. We reviewed the literature for studies involving the following antibiotics frequently used to treat critically ill adult patients receiving CRRT: vancomycin, linezolid, daptomycin, meropenem, imipenem-cilastatin, nafcillin, ampicillin-sulbactam, piperacillin-tazobactam, ticarcillin-clavulanic acid, cefazolin, cefotaxime, ceftriaxone, ceftazidime, cefepime, aztreonam, ciprofloxacin, levofloxacin, moxifloxacin, clindamycin, colistin, amikacin, gentamicin, tobramycin, fluconazole, itraconazole, voriconazole, amphotericin B (deoxycholate and lipid formulations), and acyclovir. We used these data, as well as clinical experience, to make recommendations for antibiotic dosing in critically ill patients receiving CRRT.

Linezolid disposition after standard dosages in critically ill patients undergoing continuous venovenous hemofiltration: a report of 2 cases

Linezolid is a new oxazolidinone antibiotic active against most Gram-positive microorganisms the renal elimination of which accounts for about 30% to 35% of all the clearance. Its pharmacokinetic ability was assessed during continuous venovenous hemofiltration (CVVH) in 2 anuric patients with severe postsurgical intraabdominal infections who were receiving standard dosages (600 mg intravenously twice a day). Blood samples for quantification of linezolid in plasma and in filtrate were collected after more than 4 days of therapy before dosing and at 0, 0.5, 1, 2, 3, 5, 7, 9, and 11 hours after the morning 1-hour intravenous infusion, and concentrations were determined by means of high-performance liquid chromatography. Linezolid was partially cleared by CVVH in both the patients (hemofiltration clearance [CL CVVH ] = 0.38 and 0.35 mL/min/kg), with high sieving coefficient values (0.76 to 0.92). Efficacious plasma exposure for time-dependent antibacterial activity of linezolid, either in terms of trough levels above minimum inhibitory concentration (MIC) at which 90% of the isolates are inhibited (Cmin >MIC90 ) or of area under the plasma concentration time curve to MIC90 ratio (AUC/MIC90 ) >100 hours, was ensured during CVVH in both patients. However, despite similar CL CVVH , significant interindividual pharmacokinetic variability was found in the 2 patients (AUC during the observational period [AUC 0-tau ] 334.71 versus 109.34 mg/L x h), mainly owing to substantial differences in non-CVVH-related clearance of linezolid (total CL, 0.55 versus 1.21 mL/min/kg). Our findings indicate that linezolid, although partially removed, does not warrant dosage modification during the first 48 hours when CVVH (with polysulfide hemofilter) at standard 2,000 mL/h substitution flow rate in predilution is applied to anuric patients. Thereafter, this choice is a reasonable one with the exception of those patients who have other features of linezolid toxicity and in which non-CVVH-related clearance might be impaired, although further evaluations are warranted.

Multiple-dose pharmacokinetics of linezolid during continuous venovenous haemofiltration

OBJECTIVES

Linezolid is a new antibacterial agent with a broad spectrum of activity against Gram-positive pathogens including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., and penicillin-resistant Streptococcus pneumoniae. The aim of this prospective, single-centre, open-label, two-arm study was to investigate the pharmacokinetics of linezolid during continuous venovenous haemofiltration (CVVH) in critically ill patients and to derive a dosage recommendation.

PATIENTS AND METHODS

Twenty anuric ICU patients undergoing CVVH (mean age and body weight 60.7 +/- 10.9 years and 86.0 +/- 18.0 kg) were included. All patients received linezolid 600 mg intravenously every 12 h. CVVH was performed using highly permeable polysulphone membranes (PSHF 1200, Baxter, Germany and AV 400, Fresenius, Germany). Mean blood flow rate and ultrafiltration rate were 186 +/- 15 and 40 +/- 8 mL/min, respectively. Post-dilution was performed.

RESULTS

The pharmacokinetics of linezolid in critically ill patients with acute renal failure undergoing CVVH were comparable to healthy subjects and patients without renal impairment. The elimination half-life, total clearance and haemofiltration clearance were 4.3 +/- 1.7 h, 9.3 +/- 3.5 L/h and 1.9 +/- 0.8 L/h, respectively.

CONCLUSIONS

Our results showed that linezolid was highly removable by CVVH. These data suggest that a schedule of 600 mg linezolid at least twice daily may also be an appropriate dosing for patients with severe Gram-positive infections undergoing CVVH with both types of membranes.

Removal of linezolid by conventional intermittent hemodialysis, sustained low-efficiency dialysis, or continuous venovenous hemofiltration in patients with acute renal failure

OBJECTIVE

To study the removal of linezolid, a new oxazolidinone antibiotic, by renal replacement therapy in patients with acute renal failure.

DESIGN

Prospective, single-dose pharmacokinetic study.

SETTING

Renal intensive care unit of a tertiary university hospital.

PATIENTS

Fifteen critically ill patients with oliguric acute renal failure on renal replacement therapy (seven males, mean age 72.3 yrs, range 60-94; Acute Physiology and Chronic Health Evaluation II score 24.9, range 18-36; mechanical ventilation ten of 15).

INTERVENTIONS

All patients received 600 mg of intravenous linezolid before starting renal replacement therapy, which consisted of intermittent hemodialysis lasting 3-4 hrs in eight patients, sustained low-efficiency dialysis lasting 8 hrs in five patients, and continuous venovenous hemofiltration lasting 10.5-12 hrs in two patients.

MEASUREMENTS AND MAIN RESULTS

Linezolid concentrations were measured by liquid chromatography/mass spectrometry methods on serum and dialysate/ultrafiltrate samples. At the start of renal replacement therapy, serum levels averaged 11.91 mg/L (range 5.49-21.52) and dropped at the end to levels <4 mg/dL (90% minimum inhibitory concentration values for Staphylococcus aureus) in three of eight patients on hemodialysis, three of five patients on sustained low-efficiency dialysis, and two of two patients on continuous venovenous hemofiltration. Mean removal of the drug was 193.7 mg with hemodialysis (32.3% of the dose administered), 205 mg with sustained low-efficiency dialysis (33.9%), and 74.8 mg (12.4%) and 105 (17.5%) mg following a continuous venovenous hemofiltration session lasting 10.5 and 12 hrs, respectively.

CONCLUSIONS

In patients with acute renal failure, serum levels of linezolid can be reduced to the subtherapeutic range following renal replacement therapy.