Successful treatment of methicillin-resistant Staphylococcus aureus osteomyelitis with combination therapy using linezolid and rifampicin under therapeutic drug monitoring

Linezolid is an effective antibiotic against most gram-positive bacteria including drug-resistant strains such as methicillin-resistant Staphylococcus aureus. Although linezolid therapy is known to result in thrombocytopenia, dosage adjustment or therapeutic drug monitoring of linezolid is not generally necessary. In this report, however, we describe the case of a 79-year-old woman with recurrent methicillin-resistant S. aureus osteomyelitis that was successfully treated via surgery and combination therapy using linezolid and rifampicin under therapeutic drug monitoring for maintaining an appropriate serum linezolid concentration. The patient underwent surgery for the removal of the artificial left knee joint and placement of vancomycin-impregnated bone cement beads against methicillin-resistant S. aureus after total left knee implant arthroplasty for osteoarthritis. We also initiated linezolid administration at a conventional dose of 600 mg/h at 12-h intervals, but reduced it to 300 mg/h at 12-h intervals on day 9 because of a decrease in platelet count and an increase in serum linezolid trough concentration. However, when the infection exacerbated, we again increased the linezolid dose to 600 mg/h at 12-h intervals and performed combination therapy with rifampicin, considering their synergistic effects and the control of serum linezolid trough concentration via drug interaction. Methicillin-resistant S. aureus infection improved without reducing the dose of or discontinuing linezolid. The findings in the present case suggest that therapeutic drug monitoring could be useful for ensuring the therapeutic efficacy and safety of combination therapy even in patients with osteomyelitis who require long-term antibiotic administration.

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.

Population pharmacokinetics of linezolid in critically ill patients on renal replacement therapy: comparison of equal doses in continuous venovenous haemofiltration and continuous venovenous haemodiafiltration

OBJECTIVES

Few data are available to guide linezolid dosing during renal replacement therapy. The objective of this study was to compare the population pharmacokinetics of linezolid during continuous venovenous haemofiltration (CVVHF, 30 mL/kg/h) and continuous venovenous haemodiafiltration (CVVHDF, 15 mL/kg/h + 15 mL/kg/h).

METHODS

Patients requiring linezolid 600 mg iv every 12 h and CVVHF or CVVHDF were eligible for this prospective study. Seven blood samples were collected over one dosing interval and analysed by a validated chromatographic method. Population pharmacokinetic analysis was undertaken using Pmetrics. Monte Carlo simulations evaluated achievement of a pharmacodynamics target of an AUC from 0-24 h to MIC (AUC0-24/MIC) of 80.

RESULTS

Nine CVVHDF and eight CVVHF treatments were performed in 13 patients. Regimens of CVVHDF and CVVHF were similar. A two-compartment linear model best described the data. CVVHDF was associated with a 20.5% higher mean linezolid clearance than CVVHF, without statistical significance (P = 0.39). Increasing patient weight and decreasing SOFA score were associated with increasing linezolid clearance. The mean (SD) parameter estimates were: clearance (CL), 3.8 (2.2) L/h; volume of the central compartment, 26.5 (10.3) L; intercompartmental clearance constants from central to peripheral, 8.1 (12.1) L/h; and peripheral to central compartments, 3.6 (4.0) L/h. Achievement of pharmacodynamic targets was poor for an MIC of 2 mg/L with the studied dose.

CONCLUSIONS

During CVVHF and CVVHDF, there is profound pharmacokinetic variability of linezolid. Suboptimal achievement of therapeutic targets occurs at the EUCAST breakpoint MIC of 2 mg/L using 600 mg iv every 12 h.

Linezolid-Associated Thrombocytopenia in Children With Renal Impairment

Impaired renal function has been associated with an increased risk of thrombocytopenia in adults receiving linezolid. Findings from this retrospective cohort demonstrate an association between thrombocytopenia and lower creatinine clearance in children receiving linezolid.

Optimizing therapy for vancomycin-resistant enterococcal bacteremia in children

PURPOSE OF REVIEW

Uncertainties exist regarding the optimal treatment for vancomycin-resistant enterococcal (VRE) bloodstream infections, particularly in settings in which ampicillin cannot be used.

RECENT FINDINGS

Quinupristin-dalfopristin, linezolid, and daptomycin, all approved between 1999 and 2003, represent the mainstays of therapy for VRE bacteremia, although only linezolid has been specifically approved by the United States Food and Drug Administration for this indication. The main objective of this review is to compare the relative efficacies, dosing strategies, and side-effect profiles of quinupristin-dalfopristin, linezolid, and daptomycin for VRE bacteremia in the pediatric population. A brief description of recently approved broad-spectrum Gram-positive agents that may have a role in the management of VRE bacteremia in upcoming years is also provided.

SUMMARY

Linezolid, despite its bacteriostatic activity against VRE, may be the most versatile of the available drugs. It has activity against both Enterococcus faecalis and E. faecium, can be administered orally, and resistance appears to be less of a concern with linezolid compared with the other agents. Additionally, the results of two recent meta-analyses demonstrate more favorable outcomes with linezolid compared with daptomycin for the treatment of VRE bacteremia. The clinical pharmacokinetics of linezolid have been well described in children. The most notable concern with linezolid, however, is toxicities associated with prolonged use. Until more prospective data are available, we favor linezolid as first-line therapy for the treatment of VRE bacteremia in children.

Bicytopenia, especially thrombocytopenia in hemodialysis and non-hemodialysis patients treated with linezolid therapy

One of the major adverse events associated with linezolid treatment is pancytopenia. However, there are few reports about the tolerability of linezolid among patients undergoing hemodialysis. This study retrospectively investigated the frequency of bicytopenia (thrombocytopenia and erythropenia) secondary to linezolid treatment in patients undergoing and not-undergoing hemodialysis. In total, 181 patients treated with linezolid from January 2010 to July 2012 at Aichi Medical University Hospital were divided into three groups; patients undergoing hemodialysis (HD group), those with creatinine clearance (CLCR) of <50 mL/min (CLCR < 50 group) and those with CLCR of ≥ 50 mL/min (CLCR ≥ 50 group). The incidence of thrombocytopenia, and changes in the platelet (PLT) counts during and after linezolid therapy were compared among three groups. Thrombocytopenia (<75% of the baseline level) occurred in 125 patients (69.1%). PLT reached its nadir 3-4 days after the end of linezolid therapy. In particular, the PLT nadir in HD group occurred earlier than that in non-HD groups (HD, 11.5 days [4-31 days]; CLCR < 50, 14 days [5-43 days]; CLCR ≥ 50, 15.5 days [4-49 days]; p = 0.11). HD group exhibited the greatest rate of reduction of PLT (HD, 24.0% [0.4-93.8%]; CLCR < 50, 23.8% [0.8-92.9%]; CLCR ≥ 50, 22.4% [0.92-92.9%]; p = 0.003). Finally, HD group exhibited the slowest recovery of PLT to its baseline level (HD, 10 days [5-29 days]; CLCR < 50, 9 days [2-16 days]; CLCR ≥ 50, 8 days [3-17 days]; p = 0.09). The incidence of erythropenia was not significantly different among three groups. These results indicate the need to monitor the PLT count during and after linezolid treatment in patients undergoing hemodialysis.

Clinical experience with linezolid for the treatment of orthopaedic implant infections

Gram-positive cocci are commonly isolated in orthopaedic implant infections and their resistance to β-lactams and fluoroquinolones is increasing. The high oral bioavailability of linezolid makes it an attractive oral alternative to glycopeptides and its use has increased in the last decade. To evaluate experience with linezolid in orthopaedic implant infections a systematic review of the literature available in English was undertaken. Only those articles describing series of ≥10 patients with acute or chronic orthopaedic implant infections treated with linezolid and with a clear definition of diagnosis and outcome were selected. A total of 293 patients (79.9% had prosthetic joint infections) were analysed in the 10 articles included. The overall remission rate with at least 3 months of follow-up was 79.9%, depending on whether the implant was removed or not (94% versus 69.9%). The addition of rifampicin was described in only two articles and no significant difference was observed. Adverse events were frequent during prolonged administration of linezolid (34.3%), requiring treatment discontinuation in 12.8%. The most common event was anaemia (13.4%) followed by gastrointestinal symptoms (11.1%). In conclusion, linezolid seems a good oral treatment alternative for orthopaedic implant infections due to Gram-positive cocci resistant to β-lactams and fluoroquinolones. However, close monitoring of adverse events is required.

The association between risk factors and time of onset for thrombocytopenia in Japanese patients receiving linezolid therapy: a retrospective analysis

WHAT IS KNOWN AND OBJECTIVE

Linezolid (LZD) is an oxazolidinone antibiotic that is active against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. The major adverse effect related to its use in humans is reversible myelosuppression, which mostly manifests as thrombocytopenia. This retrospective study was conducted to identify risk factors that might contribute towards the development of thrombocytopenia due to intravenous administration of LZD.

METHOD

Patients who were administered LZD between January 2008 and March 2013 were included. Thrombocytopenia was defined as a decrease in platelet count of ≥10 × 10(4) cell/μL from baseline or of ≥30%.

RESULTS

A total of 47 patients were included in this study. These patients were divided into two groups: 22 patients (46·8%) were assigned to a non-thrombocytopenia group and 25 patients (53·2%) to a thrombocytopenia group. Multivariate logistic regression analysis revealed significant intergroup differences in duration of LZD treatment [odds ratio (OR) = 1·278; 95% confidence interval (CI) = 1·068-1·529; P = 0·007] and white blood cell (WBC) count (>12000 cells/μL; OR = 10·399; 95% CI = 1·667-64·882; P = 0·012).

WHAT IS NEW AND CONCLUSIONS

This finding suggests that duration of LZD treatment and WBC count (>12000 cells/μL) are risk factors associated with thrombocytopenia resulting from LZD administration.

Treatment of mediastinitis due to methicillin-resistant Staphylococcus aureus in a renal dysfunction patient undergoing adjustments to the linezolid dose

This study is the first case report of the treatment of methicillin-resistant Staphylococcus aureus (MRSA) mediastinitis using therapeutic drug monitoring of the serum and wound exudate concentrations of linezolid in a renal dysfunction patient. In the present study, the serum trough concentration of linezolid was maintained between 2 and 7 μg/mL. Therapeutic drug monitoring dosage adjustments may be especially useful in patients with renal dysfunction and severe MRSA infection.

Platelet profile in patients with acute bacterial skin and skin structure infections receiving tedizolid or linezolid: findings from the Phase 3 ESTABLISH clinical trials

Tedizolid, the active moiety of tedizolid phosphate, is a recently approved oxazolidinone antibacterial with activity against a wide range of Gram-positive pathogens, including resistant strains such as methicillin-resistant Staphylococcus aureus. To date, 6 days of 200 mg tedizolid once daily has been shown to be noninferior to 10 days of 600 mg linezolid twice daily in two randomized, double-blind phase 3 trials (ESTABLISH-1 and ESTABLISH-2) for the treatment of patients with acute bacterial skin and skin structure infections (ABSSSIs). The intent of this study was to characterize the platelet profiles of patients receiving tedizolid relative to linezolid over the course of treatment using pooled data from these two trials. The occurrences of clinically defined and statistical analysis plan-specified reduced platelet counts were assessed at the study days 7 to 9 visit, the study days 11 to 13 visit, and the posttherapy evaluation (PTE) visit. At the study days 7 to 9 visit, incidences of reduced platelet counts were low and largely similar between the groups. The only notable difference was a lower incidence of thrombocytopenia (platelet counts, <150,000 cells/mm(3)) among patients who received tedizolid (3.2%) relative to those who received linezolid (5.6%). At the study days 11 to 13 visit, patients who received tedizolid had lower incidences of platelet counts of <150,000 cells/mm(3) (-5.9%), <112,500 cells/mm(3) (-2.4%), and <100,000 cells/mm(3) (-1.9%) than patients in the linezolid group. Similar differences were noted at the PTE visit. Findings across the two phase 3 ABSSSI trials suggest that 6 days of 200 mg tedizolid daily confers a low potential for reduced platelet counts among patients with ABSSSIs. (The ESTABLISH-1 and ESTABLISH-2 trials have been registered at ClinicalTrials.gov under registration numbers NCT01170221 and NCT01421511, respectively.).

How do we use therapeutic drug monitoring to improve outcomes from severe infections in critically ill patients?

High mortality and morbidity rates associated with severe infections in the critically ill continue to be a significant issue for the healthcare system. In view of the diverse and unique pharmacokinetic profile of drugs in this patient population, there is increasing use of therapeutic drug monitoring (TDM) in attempt to optimize the exposure of antibiotics, improve clinical outcome and minimize the emergence of antibiotic resistance. Despite this, a beneficial clinical outcome for TDM of antibiotics has only been demonstrated for aminoglycosides in a general hospital patient population. Clinical outcome studies for other antibiotics remain elusive. Further, there is significant variability among institutions with respect to the practice of TDM including the selection of patients, sampling time for concentration monitoring, methodologies of antibiotic assay, selection of PK/PD targets as well as dose optimisation strategies. The aim of this paper is to review the available evidence relating to practices of antibiotic TDM, and describe how TDM can be applied to potentially improve outcomes from severe infections in the critically ill.

Linezolid dosage in pediatric patients based on pharmacokinetics and pharmacodynamics

Linezolid pharmacokinetic profile in pediatric patients has not been fully characterized, and the dose needed to achieve a pharmacokinetic-pharmacodynamic (PK-PD) target has yet to be established because its efficacy is associated with the area under the plasma drug concentration-time curve (AUC24)/minimum inhibitory concentration (MIC) ratio. The present study aimed to define the pharmacokinetic parameters of intravenous linezolid in pediatric patients and assess the rationale for the approved dosage recommendations. Linezolid was safe, tolerated well, and clinically effective for treating Gram-positive bacteria in five pediatric patients (3-11 years). The mean values for the volume of distribution and total clearance (CL) in a one-compartment model were estimated to be 0.646 ± 0.239 l/kg and 0.171 ± 0.068 l/h/kg, respectively (mean ± S.D.). Based on this analysis, the AUC24 and trough drug concentration in plasma (C(min)) for linezolid doses were predicted to be 175.4 μg h/ml and 3.4 μg/ml for 30 mg/kg/day, 204.7 μg h/ml and 4.3 μg/ml for 35 mg/kg/day, and 263.2 μg h/ml and 6.2 μg/ml for 45 mg/kg/day, respectively. Taking into account that AUC24 should be ≥ 200 μg h/ml for MIC of 2.0 μg/ml (to achieve an AUC24/MIC ratio of ≥ 100) and C(min) should be approximately 7 μg/ml (to avoid thrombocytopenia), we consider the approved dosage of 30 mg/kg/day to be fundamentally rational, but can be underdosed against bacteria with MIC of 2.0 μg/ml; therefore, a dose of 35-45 mg/kg/day is more appropriate to ensure the efficacy and safety of linezolid in pediatric patients.

Linezolid-induced thrombocytopenia in impaired renal function: is it time for a dose adjustment? A case report and review of literature

PURPOSE

Thrombocytopenia is a common complication in the intensive care unit (ICU), but the incidence of drug-induced thrombocytopenia (DIT) is not well defined. We investigate linezolid-induced thrombocytopenia in patients with impaired renal function. Since recent studies suggest that linezolid clearance is reduced in these patients and there are no precise data confirming that dose-adjustment should be required, we performed a systematic analysis in order to establish whether it is necessary to consider a dose adjustment and promote studies to confirm this concept.

METHODS

We report a case of thrombocytopenia (nadir 32 × 10(3)/μl) in a patient with acute kidney injury who was treated with linezolid for a MRSA pulmonary infection. We performed a systematic review of the literature through PubMed with the aim to include every case report, case series, prospective and retrospective clinical study reporting linezolid-induced thrombocytopenia with concomitant impaired renal function.

RESULTS

An increasing number of clinical studies suggest a correlation between the onset of linezolid-induced thrombocytopenia and renal dysfunction. Close monitoring of platelet count and hemoglobin is recommended in patients treated with linezolid, especially in those with impaired renal function because the reduction of its clearance causes drug accumulation, as some studies have reported.

CONCLUSIONS

Clinicians should consider the potential risk of this complication, especially in elderly patients with end-stage renal disease. Further studies should be encouraged to determine if the incidence of linezolid-related thrombocytopenia could be reduced by a dose adjustment according to renal function, for which currently there is still no specific recommendation.

Risk factors for linezolid-associated thrombocytopenia in adult patients

Objectives

Thrombocytopenia (TP) is a common adverse effect of linezolid (LZD). However, risk factors for LZD-associated TP have been reported in Western patients with relatively heavy body weight. The aim of this study was to determine the risk factors for LZD-associated TP in Asian population.

Materials and methods

A retrospective cohort study was conducted among 101 consecutive patients who received LZD therapy (1,200 mg/day) between July 2003 and December 2013 at a tertiary referral hospital in Tokyo, Japan. The patients with obvious other causes for TP were excluded. The information of target infectious disease, patients’ age, gender, body weight, body mass index, baseline serum creatinine (SCr), baseline platelet count, and treatment duration was collected retrospectively. TP was defined as ≥50 % decrease in platelet count from baseline. Bi- and multi-variate analyses were performed.

Results

A total of 101 patients were included (mean age [SD] 64 [18]; male gender [%], 57 [56]). Median duration [range] of LZD therapy was 14 days [1–67]. LZD-associated TP was identified in 42 patients (42 %). For TP, adjusted odds ratio (OR) [95 % CI] of daily per kg dose (DPKD) and SCr was 1.14 [1.05–1.26] and 1.51 [1.01–2.50], respectively.

Conclusions

Higher DPKD and elevated SCr are significantly associated with LZD-associated TP. These findings suggest that daily dose of LZD should be adjusted using body weight, as typically done in pediatrics, in adults as well. Renal function also should be considered for dose adjustment.

Retrospective analysis of the risk factors for linezolid-induced thrombocytopenia in adult Japanese patients

BACKGROUND

Thrombocytopenia is a major side effect of linezolid therapy. However, there are few reports about the risk factors for linezolid-induced thrombocytopenia.

OBJECTIVE

The aim of this study is to evaluate the risk factors for thrombocytopenia in patients who undergo linezolid therapy.

SETTING

Aomori Prefectural Central Hospital in Japan, a tertiary 695 beds hospital.

METHOD

A retrospective review was performed using the hospital's medical records. From January 2010 to August 2012, 75 adult patients who received linezolid therapy were enrolled in this study.

MAIN OUTCOME MEASURE

Linezolid-induced thrombocytopenia was defined as a decrease in the patient's platelet count to <10 × 10⁴/μL or a reduction of ≥30 % from their baseline value. Odds ratios (OR) for thrombocytopenia were analyzed using multivariate stepwise logistic regression analysis.

RESULTS

Thrombocytopenia occurred in 29 patients (38.6 %), seven of whom required platelet transfusions. The patients who developed thrombocytopenia were significantly older, displayed a significantly higher frequency of renal insufficiency, and received linezolid therapy for significantly longer than the patients without thrombocytopenia. Stepwise logistic regression analysis suggested that receiving linezolid therapy for ≥14 days was a significant risk factor for thrombocytopenia [OR 13.3, 95 % confidence interval (CI) 3.2-55.6, p < 0.01], whereas the creatinine clearance rate exhibited a significant negative correlation with the incidence of the condition [OR 0.98, 95 % CI 0.96-0.99, p = 0.037]. The incidence of thrombocytopenia among the patients who demonstrated creatinine clearance rates of <30 mL/min was 60 % (12/20), which was significantly higher than that observed among the patients who displayed creatinine clearance rates of more than 60 mL/min (26.4 %, 9/34, p = 0.014).

CONCLUSION

Receiving linezolid therapy for ≥14 days and a low creatinine clearance rate were suggested to be risk factors for linezolid-induced thrombocytopenia. The platelet counts of patients with these risk factors should be closely monitored.

Treatment options for methicillin-resistant Staphylococcus aureus (MRSA) infection: Where are we now?

Methicillin-resistant Staphylococcus aureus (MRSA) infection continues to be a substantial global problem with significant associated morbidity and mortality. This review summarises the discussions that took place at the 4th MRSA Consensus Conference in relation to the current treatment options for serious MRSA infections and how to optimise whichever therapy is embarked upon. It highlights the many challenges faced by both the laboratory and clinicians in the diagnosis and treatment of MRSA infections.

Clinical population pharmacokinetics and toxicodynamics of linezolid

Thrombocytopenia is a common side effect of linezolid, an oxazolidinone antibiotic often used to treat multidrug-resistant Gram-positive bacterial infections. Various risk factors have been suggested, including linezolid dose and duration of therapy, baseline platelet counts, and renal dysfunction; still, the mechanisms behind this potentially treatment-limiting toxicity are largely unknown. A clinical study was conducted to investigate the relationship between linezolid pharmacokinetics and toxicodynamics and inform strategies to prevent and manage linezolid-associated toxicity. Forty-one patients received 42 separate treatment courses of linezolid (600 mg every 12 h). A new mechanism-based, population pharmacokinetic/toxicodynamic model was developed to describe the time course of plasma linezolid concentrations and platelets. A linezolid concentration of 8.06 mg/liter (101% between-patient variability) inhibited the synthesis of platelet precursor cells by 50%. Simulations predicted treatment durations of 5 and 7 days to carry a substantially lower risk than 10- to 28-day therapy for platelet nadirs of <100 ×10(9)/liter. The risk for toxicity did not differ noticeably between 14 and 28 days of therapy and was significantly higher for patients with lower baseline platelet counts. Due to the increased risk of toxicity after longer durations of linezolid therapy and large between-patient variability, close monitoring of patients for development of toxicity is important. Dose individualization based on plasma linezolid concentration profiles and platelet counts should be considered to minimize linezolid-associated thrombocytopenia. Overall, oxazolidinone therapy over 5 to 7 days even at relatively high doses was predicted to be as safe as 10-day therapy of 600 mg linezolid every 12 h.