Therapeutic drug monitoring: linezolid too?

Linezolid Pharmacokinetics in Critically Ill Patients: Continuous Versus Intermittent Infusion

BACKGROUND

Linezolid has been found to have considerable interindividual variability, especially in critically ill patients, which can lead to suboptimal plasma concentration. To overcome this shortcoming, several solutions have been proposed. These include using loading dose, higher maintenance doses, and dose stratification according to the patient's particularities, therapeutic drug monitoring, and drug administration via continuous infusion (CI) instead of intermittent infusion (II). In the present study, we aim to compare the pharmacokinetic (PK) parameters of linezolid after administration as II versus CI to critically ill patients.

METHODS

In a prospective study conducted in an intensive care unit, we compared the same two daily doses of linezolid administered via II versus CI. The serum concentration was measured, and pharmacokinetic parameters were calculated. The pharmacokinetic/pharmacodynamic (PK/PD) indices for efficacy chosen were area under the concentration-time curve at steady state divided by the minimum inhibitory concentration over 80 (AUC24-48/MIC > 80).

RESULTS

Greater serum concentration variability was observed in the II group than in the CI group. The %T > MIC > 80% was achieved for MICs of 1 and 2 µg/mL 100% of the time, whereas for the II group, this was 93% and 73%, respectively. AUC24-48/MIC > 80 was reached in 100% of cases in the CI group compared with 87% in the II group for a MIC of 1 µg/mL.

CONCLUSIONS

The two infusion methods may be used comparably, but utilizing CI as an alternative to II may have potential benefits, including avoiding periods of suboptimal concentrations, which may enhance safety profiles and clinical outcomes. Considering the relatively few studies performed on linezolid to date, which are increasing in number, the results of the present study may be of interest.

Individualized antibiotic dosage regimens for patients with augmented renal clearance

Objectives: Augmented renal clearance (ARC) is a state of enhanced renal function commonly observed in 30%-65% of critically ill patients despite normal serum creatinine levels. Using unadjusted standard dosing regimens of renally eliminated drugs in ARC patients often leads to subtherapeutic concentrations, poor clinical outcomes, and the emergence of multidrug-resistant bacteria. We summarized pharmaceutical, pharmacokinetic, and pharmacodynamic research on the definition, underlying mechanisms, and risk factors of ARC to guide individualized dosing of antibiotics and various strategies for optimizing outcomes. Methods: We searched for articles between 2010 and 2022 in the MEDLINE database about ARC patients and antibiotics and further provided individualized antibiotic dosage regimens for patients with ARC. Results: 25 antibiotic dosage regimens for patients with ARC and various strategies for optimization of outcomes, such as extended infusion time, continuous infusion, increased dosage, and combination regimens, were summarized according to previous research. Conclusion: ARC patients, especially critically ill patients, need to make individualized adjustments to antibiotics, including dose, frequency, and method of administration. Further comprehensive research is required to determine ARC staging, expand the range of recommended antibiotics, and establish individualized dosing guidelines for ARC patients.

A 600 mg of fixed-dose linezolid in renally impaired patients versus 15 mg/kg intermittent dose-optimized vancomycin in renally non-impaired patients: A single centre retrospective analysis for adult patients with hospital-acquired pneumonia due to methicillin-resistant Staphylococcus aureus

OBJECTIVES

Both linezolid and vancomycin are approved by USFDA and IDSA guidelines for the management of nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) in clinical practice. Baseline creatinine clearance is the criterion for prescribing vancomycin or linezolid for hospital-acquired pneumonia in our institution. However, patients with renal function impairment are far more difficult to manage in intensive care. Thus, the objectives of the study were to compare the clinical efficacy and safety of 600 mg of fixed-dose linezolid with intermittent dose-optimised vancomycin in hospital-acquired pneumonia due to MRSA and to evaluate parameters of clinical cure.

METHODS

Analysis of a review of patients' charts. Patients with creatinine clearance <80 ml/min received 600 mg linezolid/12 h (n = 139, LN cohort), and patients with creatinine clearance ≥80 ml/min received intravenous 15 mg/kg vancomycin/12 h for 1-2 weeks consecutively or 3 weeks in case of bacteremia (n = 152, VC cohort) for management of hospital-acquired pneumonia due to MRSA.

RESULTS

A 59% of patients from the LN cohort and 47% of patients from the VC cohort were clinically cured. Administration of systemic steroids (p = 0.0412) and ≥ 80 ml/min creatinine clearance (p = 0.0498) were the independent parameters for the clinical cure of patients. Nephrotoxicity was higher among patients of the VC cohort than the LN cohort (p = 0.0464). Treatment failed in 41% of patients from the LN cohort and in 53% of patients from the VC cohort (p = 0.0200).

CONCLUSIONS

A 600 mg of fixed-dose linezolid is an ideal alternative to intermittent dose-optimised vancomycin for better clinical outcomes for patients with hospital-acquired pneumonia due to MRSA, especially for patients with renal impairment.

Safety of linezolid in patients with decreased renal function and trough monitoring: a systematic review and meta-analysis

BACKGROUND

Linezolid causes hematological toxicity, mostly thrombocytopenia, which leads to treatment discontinuation and failure. Recent studies revealed that during linezolid therapy, the incidence of treatment-related hematological toxicity is significantly higher in patients with decreased renal function (DRF) than in those with normal renal function. Linezolid monitoring is necessary due to the high frequency of hematological toxicity in patients with DRF and the relationship between blood concentration and safety. We performed a systematic review and meta-analysis to evaluate the safety correlation between DRF and trough monitoring.

METHODS

Articles published before June 24, 2022, on MEDLINE, Web of Sciences, Cochrane Register of Controlled Trials, and ClinicalTrials.gov were systematically analyzed. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using the Mantel-Haenszel method and the variable effects model.

RESULTS

The incidence of hematological toxicity was significantly higher in patients with DRF than in those without DRF (OR = 2.37; p < 0.001). Subgroup analysis, performed according to hematotoxicity classification, including thrombocytopenia, anemia, and pancytopenia, revealed a significantly higher incidence of thrombocytopenia (OR = 2.45; p < 0.001) and anemia (OR = 2.31; p = 0.006) in patients with DRF than in those without; pancytopenia (OR = 1.41; p = 0.80) incidences were not significantly higher. Based on a systematic review, linezolid trough concentrations > 6-7 μg/mL may be associated with an increased incidence of thrombocytopenia. However, no confidential threshold values for the development of thrombocytopenia were found in the area under the concentration curve values for children or adults.

CONCLUSION

We observed a high frequency of hematological toxicity during linezolid therapy in patients with DRF. To ensure safety, linezolid trough concentrations should be ≤6-7 μg/mL.

Serum linezolid concentrations are reduced in critically ill patients with pulmonary infections: A prospective observational study

RATIONALE

The concentration-time profile of linezolid varies considerably in critically ill patients. Question of interest is, if the site of infection influences linezolid serum concentrations.

METHODS

68 critically ill patients, treated with linezolid, were included. The concentration-time-profile for linezolid was determined using maximum a-posteriori predictions. A trough concentration (C_min) between 2 and 10 mg/L was defined as the target. A generalized linear model (GLM) was established to evaluate potential covariates.

RESULTS

The indications for linezolid therapy were in descending order: peritonitis (38.2%), pneumonia (25.0%), infectious acute respiratory distress syndrome (ARDS) (19.1%), and other non-pulmonary infection (17.7%). 27.2 and 7.9% of C_min were subtherapeutic and toxic, respectively. In the GLM, ARDS (mean: -2.1 mg/L, CI: -3.0 to -1.2 mg/L) and pneumonia (mean: -2.2 mg/L, CI: -2.8 to -1.6 mg/L) were significant (p < 0.001) determinants of C_min. Patients with ARDS (mean: 2.3 mg/L, 51.2% subtherapeutic, 0.0% toxic) and pneumonia (mean: 3.5 mg/L, 41.5% subtherapeutic, 7.7% toxic) had significantly (p < 0.001) lower C_min than those with peritonitis (mean: 5.5 mg/L, 14.4% subtherapeutic, 9.3% toxic) and other non-pulmonary infection (mean: 5.2 mg/L, 3.3% subtherapeutic, 16.5% toxic).

CONCLUSION

Linezolid serum concentrations are reduced in patients with pulmonary infections. Future studies should investigate if other linezolid thresholds are needed in those patients due to linezolid pooling in patients´ lung.

Protein-Induced Fluorescence Enhancement and Quenching in a Homogeneous DNA-Based Assay for Rapid Detection of Small-Molecule Drugs in Human Plasma

Homogeneous assays for determining the concentration of small molecules in biological fluids are of importance for monitoring blood levels of critical drugs in patients. We have developed a strand displacement competition assay for the drugs dabigatran, methotrexate, and linezolid, which allows detection and determination of the concentration of the drugs in plasma; however, a surprising kinetic behavior of the assay was observed with an initial rapid change in apparent FRET values. We found that protein-induced fluorescent enhancement or quenching (PIFE/Q) caused the initial change in fluorescence within the first minute after addition of protein, which could be exploited to construct assays for concentration determination within minutes in the low nanomolar range in plasma. A kinetic model for the assay was established, and when taking the new finding into account, the in silico simulations were in good agreement with the experimentally observed results. Utilizing these findings, a simpler assay was constructed for detection of dabigatran, which allowed for detection within minutes without any time dependencies.

Linezolid Administration to Critically Ill Patients: Intermittent or Continuous Infusion? A Systematic Literature Search and Review

A judicious antibiotic therapy is one of the challenges in the therapy of critically ill patients with sepsis and septic shock. The pathophysiological changes in these patients significantly alter the antibiotic pharmacokinetics (PK) and pharmacodynamics (PD) with important consequences in reaching the therapeutic targets or the risk of side effects. The use of linezolid, an oxazolidinone antibiotic, in intensive care is such an example. The optimization of its therapeutic effects, administration in intermittent (II) or continuous infusion (CI) is gaining increased interest. In a systematic review of the main databases, we propose a detailed analysis of the main PK/PD determinants, their relationship with the clinical therapeutic response and the occurrence of adverse effects following II or CI of linezolid to different classes of critically ill patients or in Monte Carlo simulations.

Successful treatment of linezolid-induced severe lactic acidosis with continuous venovenous hemodiafiltration: A case report

Linezolid is an oxazolidinone antibiotic. Linezolid-associated lactic acidosis has been reported in 6.8% of linezolid-treated patients. Lactic acidosis is associated with poor clinical outcomes, with high blood lactate levels resulting in organ dysfunction and mortality. This case report describes the development of lactic acidosis in a 64-year-old Chinese woman who had received 33 days of treatment with antituberculosis drugs and 28 days of treatment with oral linezolid for tuberculous meningitis. Severe lactic acidosis was reversed by withdrawing antituberculosis drugs and using continuous venovenous hemodiafiltration (CVVH). When the patient's condition was stable, she was transferred to the infectious disease department, and antituberculosis drugs, with the exception of linezolid, were reintroduced. This did not result in recurrence of lactic acidosis. The causal relationship between lactic acidosis and linezolid was categorized as 'probable' on the Adverse Drug Reaction Probability Scale. This case demonstrates that CVVH has potential as an alternative to discontinuation of linezolid alone for rapid reversal of linezolid-associated severe lactic acidosis.

Applicability of vancomycin, meropenem, and linezolid in capillary microsamples vs. dried blood spots: A pilot study for microsampling in critically ill children

INTRODUCTION

Therapeutic drug monitoring (TDM) has been shown to be clinically beneficial for critically ill patients. However, this is a burden for neonates or children with small circulating blood volumes. Here, we aimed to develop and validate a microsampling TDM platform (including dried blood spots (DBS) and capillary microsamples (CMS)) for the simultaneous quantification of vancomycin, meropenem, and linezolid.

METHODS

Paired DBS and CMS samples were obtained from an intensive care unit (ICU) to evaluate its clinical application. Estimated plasma concentrations (EPC) were calculated from DBS concentrations. Agreement between methods was evaluated using Deming regression and Bland-Altman difference plots.

RESULTS

The microsampling methods validation showed excellent reliability and compatibility with the analysis of the sample matrix and hematocrit range of the studied population. The DBS and CMS accuracy and precision results were within accepted ranges and samples were stable at room temperature for at least 2 days and 8 h, respectively. Hematocrit had no impact on CMS, but sightly impacted DBS measurements. The CMS and DBS antibiotic concentrations correlated well (r > 0.98). The drug concentration ratio in DBS samples to that in CMS was 1.39 for vancomycin, 1.34 for meropenem, and 0.94 for linezolid. The EPC calculated from the DBS using individual hematocrit ranges presented comparable absolute values for vancomycin (slope: 1.06) and meropenem (slope: 1.04), with a mean of 98% and 99% of the measured CMS concentrations, respectively.

DISCUSSION

This study provides a microsampling TDM platform validated for clinical use for a rapid quantification of three antibiotics and is suitable for real-time TDM-guided personalization of antimicrobial treatment in critically ill children.

Pharmacokinetics of Linezolid Dose Adjustment for Creatinine Clearance in Critically Ill Patients: A Multicenter, Prospective, Open-Label, Observational Study

Purpose

The aim of this study is to use a population pharmacokinetic (PK) approach to evaluate the optimal dosing strategy for linezolid (LNZ) in critically ill patients.

Methods

This multicenter, prospective, open-label, observational study was conducted in 152 patients, and 117 of them were included in the PK model, whereas the rest were in the validation group. The percentage of therapeutic target attainment (PTTA) comprising two pharmacodynamic indices and one toxicity index was used to evaluate dosing regimens based on Monte Carlo simulations stratified by low, normal, and high renal clearance for MICs of 0.25–4 mg/L.

Results

A single-compartment model with a covariate creatinine clearance (CrCL) was chosen as the final model. The PK parameter estimates were clearance of 5.60 L/h, with CrCL adjustment factor of 0.386, and a distribution volume of 43.4 L. For MIC ≤2 mg/L, the standard dosing regimen (600 mg q12h) for patients with severe renal impairment (CrCL, 40 mL/min) and standard dosing or 900 mg q12h for patients with normal renal functions (CrCL, 80 mL/min) could achieve PTTA ≥74%. The dose of 2400 mg per 24-h continuous infusion was ideal for augmented renal clearance (ARC) with MIC ≤1 mg/L. For MICs >2 mg/L, rare optimal dose regimens were found regardless of renal function.

Conclusion

In critically ill patients, the standard dose of 600 mg q12h was sufficient for MIC ≤2 mg/L in patients without ARC. Moreover, a 2400 mg/day 24-h continuous infusion was recommended for ARC patients.

Dosage Individualization of Linezolid: Precision Dosing of Linezolid To Optimize Efficacy and Minimize Toxicity

The high interindividual variability in the pharmacokinetics (PK) of linezolid has been described, which results in an unacceptably high proportion of patients with either suboptimal or potentially toxic concentrations following the administration of a fixed regimen. The aim of this study was to develop a population pharmacokinetic model of linezolid and use this to build and validate alogorithms for individualized dosing. A retrospective pharmacokinetic analysis was performed using data from 338 hospitalized patients (65.4% male, 65.5 [±14.6] years) who underwent routine therapeutic drug monitoring for linezolid. Linezolid concentrations were analyzed by using high-performance liquid chromatography. Population pharmacokinetic modeling was performed using a nonparametric methodology with Pmetrics, and Monte Carlo simulations were employed to calculate the 100% time >MIC after the administration of a fixed regimen of 600 mg administered every 12 h (q12h) intravenously (i.v.). The dose of linezolid needed to achieve a PTA ≥ 90% for all susceptible isolates classified according to EUCAST was estimated to be as high as 2,400 mg q12h, which is 4 times higher than the maximum licensed linezolid dose. The final PK model was then used to construct software for dosage individualization, and the performance of the software was assessed using 10 new patients not used to construct the original population PK model. A three-compartment model with an absorptive compartment with zero-order i.v. input and first-order clearance from the central compartment best described the data. The dose optimization software tracked patients with a high degree of accuracy. The software may be a clinically useful tool to adjust linezolid dosages in real time to achieve prespecified drug exposure targets. A further prospective study is needed to examine the potential clinical utility of individualized therapy.

Proactive therapeutic drug monitoring (TDM) may be helpful in managing long-term treatment with linezolid safely: findings from a monocentric, prospective, open-label, interventional study

BACKGROUND

Thrombocytopenia may be a dose-dependent adverse effect of linezolid therapy.

OBJECTIVES

To assess whether proactive therapeutic drug monitoring (TDM) could be helpful in preventing and/or in recovering from the occurrence of linezolid-induced thrombocytopenia during long-term treatment.

METHODS

This was a monocentric, prospective, open-label, interventional study conducted between June 2015 and December 2017 among adult patients receiving >10 days of linezolid therapy and undergoing proactive TDM (desired trough level 2-8 mg/L) and platelet count assessment at day 3-5 and then once weekly up to the end of treatment.

RESULTS

Sixty-one patients were included. Twenty-eight (45.9%) always had desired trough level (group A) and 33 (54.1%) experienced linezolid overexposure (group B) [29/33 transiently (subgroup B1) and 4/33 persistently (subgroup B2)]. No patient experienced linezolid underexposure. Median duration of treatment for the different groups ranged between 19 and 54 days. Thrombocytopenia occurred overall in 14.8% of cases (9/61). The incidence rate of thrombocytopenia was significantly lower (P=0.012) in both group A (10.7%; 3/28) and subgroup B1 (10.3%; 3/29) than in subgroup B2 (75.0%; 3/4). Thrombocytopenic patients belonging to both group A and group B1 recovered from thrombocytopenia without the need for discontinuing therapy. Multivariate linear regression analysis revealed that thrombocytopenia was independently associated with baseline platelet count and with median linezolid trough concentrations.

CONCLUSIONS

Proactive TDM of linezolid may be beneficial either in preventing or in recovering from dose-dependent thrombocytopenia, even when treatment lasts for more than 28 days. Larger prospective studies are warranted to confirm our findings.

Population Pharmacokinetics and Dosage Optimization of Linezolid in Patients with Liver Dysfunction

Linezolid is the first synthetic oxazolidone agent to treat infections caused by Gram-positive pathogens. Infected patients with liver dysfunction (LD) are more likely to suffer from adverse reactions, such as thrombocytopenia, when standard-dose linezolid is used than patients with LD who did not use linezolid. Currently, pharmacokinetics data of linezolid in patients with LD are limited. This study aimed to characterize pharmacokinetics parameters of linezolid in patients with LD, identify the factors influencing the pharmacokinetics, and propose an optimal dosage regimen. We conducted a prospective study and established a population pharmacokinetics model with the Phoenix NLME software. The final model was evaluated by goodness-of-fit plots, bootstrap analysis, and prediction corrected-visual predictive check. A total of 163 concentration samples from 45 patients with LD were adequately described by a one-compartment model with first-order elimination along with prothrombin activity (PTA) and creatinine clearance as significant covariates. Linezolid clearance (CL) was 2.68 liters/h (95% confidence interval [CI], 2.34 to 3.03 liters/h); the volume of distribution (V) was 58.34 liters (95% CI, 48.00 to 68.68 liters). Model-based simulation indicated that the conventional dose was at risk for overexposure in patients with LD or severe renal dysfunction; reduced dosage (300 mg/12 h) would be appropriate to achieve safe (minimum steady-state concentration [C _min,ss] at 2 to 8 μg/ml) and effective targets (the ratio of area under the concentration-time curve from 0 to 24 h [AUC_0-24] at steady state to MIC, 80 to 100). In addition, for patients with severe LD (PTA, ≤20%), the dosage (400 mg/24 h) was sufficient at an MIC of ≤2 μg/ml. This study recommended therapeutic drug monitoring for patients with LD. (This study has been registered in the Chinese Clinical Trial Registry under no. ChiCTR1900022118.).

Impact of augmented renal clearance on the pharmacokinetics of linezolid: Advantages of continuous infusion from a pharmacokinetic/pharmacodynamic perspective

OBJECTIVES

The aim of this study was to assess the influence of renal function, in particular the presence of augmented renal clearance (ARC), on the pharmacokinetics of linezolid in critically ill patients. The effect of continuous infusion on the probability of therapeutic success from a pharmacokinetic/pharmacodynamic (PK/PD) perspective was also evaluated.

METHODS

Seventeen patients received linezolid (600 mg every 12 h) as a 30-min infusion and 26 as a continuous infusion (50 mg/h). The PK parameters were calculated and the probability of PK/PD target attainment (PTA) was estimated by Monte Carlo simulation (MCS) for different doses administered by intermittent (600 mg every 12 h or 600 mg every 8 h) or continuous infusion (50 mg/h or 75 mg/h).

RESULTS

In patients without ARC, the standard dose was adequate to attain the PK/PD target. However, linezolid clearance was significantly higher in ARC patients, leading to sub-therapeutic concentrations. Continuous infusion (50 mg/h) provided concentrations ≥2 mg/l in 70% of the ARC patients. MCS revealed that concentrations ≥2 mg/l would be reached in >90% of patients receiving 75 mg/h.

CONCLUSIONS

ARC increases linezolid clearance and leads to a high risk of underexposure with the standard dose. Continuous infusion increases the PTA, but an infusion rate of 75 mg/h should be considered to ensure concentrations ≥2 mg/ml.

Novel Population Pharmacokinetic Model for Linezolid in Critically Ill Patients and Evaluation of the Adequacy of the Current Dosing Recommendation

Antimicrobial treatment in critically ill patients remains challenging. The aim of this study was to develop a population pharmacokinetic model for linezolid in critically ill patients and to evaluate the adequacy of current dosing recommendation (600 mg/12 h). Forty inpatients were included, 23 of whom were subjected to continuous renal replacement therapies (CRRT). Blood and effluent samples were drawn after linezolid administration at defined time points, and linezolid levels were measured. A population pharmacokinetic model was developed, using NONMEM 7.3. The percentage of patients that achieved the pharmacokinetic/pharmacodynamic (PK/PD) targets was calculated (AUC₂₄/MIC > 80 and 100% T_>MIC). A two-compartment model best described the pharmacokinetics of linezolid. Elimination was conditioned by the creatinine clearance and by the extra-corporeal clearance if the patient was subjected to CRRT. For most patients, the standard dose of linezolid did not cover infections caused by pathogens with MIC ≥ 2 mg/L. Continuous infusion may be an alternative, especially when renal function is preserved.

Voltammetric monitoring of linezolid, meropenem and theophylline in plasma

Treatment of healthcare associated Pneumonia (HCAP) caused by Methicillin-resistant Staphylococcus aureus (MRSA) requires therapeutic protocols formed of linezolid (LIN) either alone or in combination with meropenem (MERO) and theophylline (THEO). The inter-individual pharmacokinetic variations require the development of reliable therapeutic drug monitoring (TDM) tools especially in immunocompromised patients. A sensitive square wave voltammetric sensor using multiwalled carbon nanotubes (MWCNTs) modified carbon paste electrode in Britton-Robinson buffer was developed and validated. Experimental parameters such as pH, percentage of MWCNTs, and pre-concentration time were optimized. The sensor was employed at pH 11.0 for the determination of LIN in plasma within a concentration range of 2.5 × 10^-8 - 8.0 × 10^-6 mol L^-1without interference from co-administered medications. On the other hand, simultaneous monitoring of LIN, MERO and THEO in plasma was feasible at pH 3.0 over concentration ranges of 4.0 × 10^-7- 9.0 × 10^-5, 8.0 × 10^-7- 9.0 × 10^-5 and 8.0 × 10^-7 - 9.0 × 10^-5 mol L^-1, respectively. The performance of the proposed sensor was validated and the applicability for TDM has been demonstrated in plasma of healthy volunteers.

Variable Linezolid Exposure in Intensive Care Unit Patients-Possible Role of Drug-Drug Interactions

BACKGROUND

Standard doses of linezolid may not be suitable for all patient groups. Intensive care unit (ICU) patients in particular may be at risk of inadequate concentrations. This study investigated variability of drug exposure and its potential sources in this population.

METHODS

Plasma concentrations of linezolid were determined by high-performance liquid chromatography in a convenience sample of 20 ICU patients treated with intravenous linezolid 600 mg twice daily. Ultrafiltration applying physiological conditions (pH 7.4/37°C) was used to determine the unbound fraction. Individual pharmacokinetic (PK) parameters were estimated by population PK modeling. As measures of exposure to linezolid, area under the concentration-time curve (AUC) and trough concentrations (Cmin) were calculated and compared with published therapeutic ranges (AUC 200-400 mg*h/L, Cmin 2-10 mg/L). Coadministered inhibitors or inducers of cytochrome P450 and/or P-glycoprotein were noted.

RESULTS

Data from 18 patients were included into the PK evaluation. Drug exposure was highly variable (median, range: AUC 185, 48-618 mg*h/L, calculated Cmin 2.92, 0.0062-18.9 mg/L), and only a minority of patients had values within the target ranges (6 and 7, respectively). AUC and Cmin were linearly correlated (R = 0.98), and classification of patients (underexposed/within therapeutic range/overexposed) according to AUC or Cmin was concordant in 15 cases. Coadministration of inhibitors was associated with a trend to higher drug exposure, whereas 3 patients treated with levothyroxine showed exceedingly low drug exposure (AUC ∼60 mg*h/L, Cmin <0.4 mg/L). The median unbound fraction in all 20 patients was 90.9%.

CONCLUSIONS

Drug exposure after standard doses of linezolid is highly variable and difficult to predict in ICU patients, and therapeutic drug monitoring seems advisable. PK drug-drug interactions might partly be responsible and should be further investigated; protein binding appears to be stable and irrelevant.

The use of liquid chromatography-tandem mass spectrometry for therapeutic drug monitoring of antibiotics in cancer patients

Cancer remains a leading cause of mortality and morbidity worldwide. In addition to organ failure, the most frequent reasons for admission of cancer patients to intensive care units (ICU) are: infections and sepsis. As critically ill, the complexity of the health situation of cancer patients renders the standard antimicrobial regimen more complex and even inadequate which results in increased mortality rates. This is due to pathophysiological changes in the volume of distribution, increased clearance, as well as to organ dysfunction. While in the former cases a decrease in drug efficacy is observed, the hallmark of the latter one is overdosing leading to increased toxicity at the expense of efficacy. Furthermore, an additional risk factor is the potential drug-drug interaction between antibiotics and antineoplastic agents. Therefore, therapeutic drug monitoring (TDM) is a necessity to improve the clinical outcome of antimicrobial therapy in cancer patients. To be applied in routine analysis the method used for TDM should be cheap, fast and highly accurate/sensitive. Furthermore, as ICU patients are treated with a cocktail of antibiotics the method has to cover the simultaneous analysis of antibiotics used as a first/second line of treatment. The aim of the current review is to briefly survey the pitfalls in the current antimicrobial therapy and the central role of TDM in dose adjustment and drug-drug interaction’s evaluation. A major section is dedicated to summarize the currently published analytical methods and to shed light on the difficulties and potential problems that can be encountered during method development.

A 1 year retrospective audit of quality indicators of clinical pharmacological advice for personalized linezolid dosing: one stone for two birds?

AIM

This study explored the clinical and economic impact of clinical pharmacological advice (CPA) (based on therapeutic drug monitoring [TDM] results, and on patients' characteristics and co-medications) on personalized linezolid therapy in a tertiary care hospital.

METHODS

A 1 year retrospective analysis of quality indicators of CPA (clinicians' adherence rate to CPA, pre-post rate of linezolid trough concentrations within the desired range and cost balance analysis) was conducted.

RESULTS

Five hundred and forty-four CPAs were provided to clinicians during 2014 for personalizing linezolid therapy in 168 patients. Clinicians' adherence to CPAs was very high (94.7%). The pre-post rate of linezolid Cmin distribution showed a favourable impact of CPA on patient care (pre-post ratio of Cmin within the desired range + 23.4%, pre, 51.2% vs. post, 74.6%). Overall, linezolid dosage was mainly reduced (56.9% of cases), whereas dose augmentation was needed only in a minority of cases (7.7%). Cost balance analysis showed that overall 1258 standard doses of linezolid (unitary dose 600 mg) were spared for treating 168 patients with a personalized dosage for a median duration of 11 days (range 3-128 days) with a cost saving of 60038.05 €.

CONCLUSION

Active computerized advice elaborated by the clinical pharmacologist on the basis of TDM results and of patient's pathophysiological data and co-medications may be cost-effective for personalizing linezolid treatment.