Linezolid and lactic acidosis: a role for lactate monitoring with long-term linezolid use in children

Risk of medication-induced lactic acidosis and hyperlactatemia: a pharmacovigilance study of the United States Food and Drug Administration's Adverse Event Reporting System database

Objective

Lactic acidosis and hyperlactatemia (LAHL) are predictors of poor clinical outcomes in critically ill patients. This research aimed to specify medications reported in association with LAHL, thus providing valuable insights into medication safety.

Methods

Spontaneous reports were excavated from the United States Food and Drug Administration's Adverse Event Reporting System (FAERS) database from Q1 2004 to Q2 2024. Adverse reaction signals of medication-induced lactic acidosis and hyperlactatemia (MILAHL) were detected by reporting odds ratio (ROR) and proportional reporting ratio (PRR).

Results

1,055 medications were identified as primary suspect medications of LAHL from Q1 2004 to Q2 2024, of which 180 were considered to have risk signals by ROR and 160 by PRR. Metformin (16,439 cases), linezolid (815 cases), amlodipine (646 cases), salbutamol (531 cases), and paracetamol (417 cases) were the top 5 medications with the most cases of LAHL. Among the top 50 medications with the strongest ROR and PRR signal, 16 were systemic antivirals, and 13 were antidiabetics (9 containing metformin). 23 of the top 50 medications with the strongest ROR and PRR signal did not indicate the risk of LAHL in the Summary of Product Characteristics (SmPC).

Conclusion

This study listed high-risk medications by ROR and PRR analysis, especially those without an LAHL warning in SmPC, to help health professionals identify MILAHL in case of elevated lactate and enhance medication safety monitoring.

Linezolid-Induced Lactic Acidosis Presenting As Acute Cholecystitis: A Case Report and Systematic Review

Linezolid has gained increased use for the treatment of infections caused by multidrug-resistant Gram-positive bacteria in recent years. It can cause rare but potentially life-threatening lactic acidosis. Here, we presented a case report of linezolid-induced lactic acidosis (LILA), along with a systematic review of current literature. The patient was a 55-year-old male who presented with the symptoms of acute cholecystitis. He had been treated for sepsis due to acute cholecystitis with broad-spectrum antibiotics and intravenous fluids as per protocol. Still, his lactate level was getting elevated. After excluding other causes of lactic acidosis, LILA was diagnosed, and linezolid was discontinued. His lactic acid level, as well as his physical condition, improved after that. Studies related to LILA were searched in Medline via PubMed. After screening titles, abstracts, and full texts, data were extracted, tabulated, and presented in this article. The risk of bias was also assessed. We found 78 relevant articles in the primary search, and 26 articles, including 496 patients, were included in the study. From 23 studies of 129 patients, 28 patients (21.7%) died in the setting of LILA. The peak lactate level in which the patient developed LILA was 38.1 mmol/L after four weeks of therapy. The most common health conditions associated with LILA were end-stage renal failure (ESRD), diabetes mellitus (DM), hypertension, chronic obstructive pulmonary disease (COPD), etc. Eighteen studies with a total of 30 patients discontinued it after the development of LILA. Twenty-four patients (80%) out of 30 survived after the discontinuation. We recommend including LILA in the differential diagnoses when treating patients with lactic acidosis since LILA is associated with a relatively elevated mortality rate.

A Mitocentric View of the Main Bacterial and Parasitic Infectious Diseases in the Pediatric Population

Infectious diseases occur worldwide with great frequency in both adults and children. Both infections and their treatments trigger mitochondrial interactions at multiple levels: (i) incorporation of damaged or mutated proteins to the complexes of the electron transport chain, (ii) mitochondrial genome (depletion, deletions, and point mutations) and mitochondrial dynamics (fusion and fission), (iii) membrane potential, (iv) apoptotic regulation, (v) generation of reactive oxygen species, among others. Such alterations may result in serious adverse clinical events with great impact on children's quality of life, even resulting in death. As such, bacterial agents are frequently associated with loss of mitochondrial membrane potential and cytochrome c release, ultimately leading to mitochondrial apoptosis by activation of caspases-3 and -9. Using Rayyan QCRI software for systematic reviews, we explore the association between mitochondrial alterations and pediatric infections including (i) bacterial: M. tuberculosis, E. cloacae, P. mirabilis, E. coli, S. enterica, S. aureus, S. pneumoniae, N. meningitidis and (ii) parasitic: P. falciparum. We analyze how these pediatric infections and their treatments may lead to mitochondrial deterioration in this especially vulnerable population, with the intention of improving both the understanding of these diseases and their management in clinical practice.

Incidence and Associated Risk Factors for Lactic Acidosis Induced by Linezolid Therapy in a Case-Control Study in Patients Older Than 85 Years

Background: Serum lactic acid is considered a prognostic indicator in critically ill patients. However, studies on linezolid-induced lactic acidosis (LILA) are still limited. Individuals older than 85 years old (very elderly) have limited capacity for organ compensation, and LILA data from these patients are lacking. In this study, we evaluated the risk factors for LILA in patients older than 85 years and established a risk prediction model for geriatric practice.

Methods: In this retrospective cohort study, blood gas analysis data and arterial lactate levels were monitored in patients older than 85 years during the use of teicoplanin or linezolid. After propensity score matching analyses, we compared the incidence of lactic acidosis between the teicoplanin and linezolid therapy groups and identified the risk factors of LILA.

Results: The incidence of lactic acidosis was found to be much lower in the group receiving teicoplanin than those receiving linezolid therapy (0 vs. 35.7%; p < 0.0001). A duration of linezolid therapy ≥ 9 days [odds ratio (OR), 3.541; 95% confidence interval (CI), 1.161–10.793; p = 0.026], an arterial blood glucose level ≥ 8 mmol/L (OR, 4.548; 95% CI, 1.507–13.725; p = 0.007), and a high sequential organ failure assessment score (OR, 1.429; 95% CI, 1.213–1.685; p < 0.0001) were risk factors for LILA. The constructed risk model could be used to predict LILA (area under the curve, 0.849; specificity, 65.1%; sensitivity, 91.4%, with a negative predictive value of 93.2% and a positive predictive value of 59.3%).

Conclusions: LILA can occur in patients older than 85 years after a relatively shorter duration of linezolid therapy. Therefore, close monitoring of blood gas and arterial lactate levels during linezolid therapy in the very elderly population is necessary.

Effect of a serum lactate monitoring recommendation policy on patients treated with linezolid

Lactic acidosis is one of the most fatal adverse effects of linezolid, an antibiotic used to treat serious infections caused by antibiotic-resistant bacteria. However, the measures to prevent lactic acidosis have not been well established.We performed a retrospective study to analyze the impact of applying a serum lactate monitoring recommendation policy in patients treated with linezolid.Since September 2011, we have recommended inpatient monitoring of serum lactate levels in patients treated with linezolid at our hospital. Patients were divided into two groups according to whether they were seen during the non-recommendation or recommendation periods. The frequency of serum lactate monitoring, linezolid-induced lactatemia, lactic acidosis, critical illness, and death were compared between the two periods.After September 2011, adherence to the recommendation to monitor serum lactate increased from 6.1% to 60.1%. No difference was observed in the incidence of linezolid-induced lactatemia and lactic acidosis between the two periods. However, there was a significant difference in the incidence of linezolid-induced critical illness between the non-recommendation and recommendation periods (3 vs 0 cases, P = .044).In patients treated with linezolid, serum lactate monitoring led to early detection of lactatemia, thus enabling rapid rescue. We recommend regular monitoring of serum lactate in all patients treated with linezolid.

Linezolid Induced Lactic Acidosis: The Side Effect, Clinician Should Be Aware of

Linezolid is a synthetic antibiotic that functions through the inhibition of bacterial protein synthesis by binding to ribosomal ribonucleic acid (rRNA). Deliverable in both intravenous and oral form, with a low level of resistance amongst Methicillin-resistant Staphylococcus aureus (MRSA) strains, it is recommended for a wide range of gram-positive infections. We present a case of a male patient who underwent endovascular abdominal aortic aneurysm repair complicated by abdominal sepsis due to bowel ischemia; several days after linezolid therapy was initiated, he presented with signs of lactic acidosis. After excluding other sources such as metabolic, hypoxia, or organ damage, the resulting lactic acidosis was determined to be a side effect of linezolid.

Neonatal and Neurodevelopmental Outcomes Following Linezolid for Coagulase-negative Staphylococcal Infection: Real World Evidence

BACKGROUND

Coagulase-negative staphylococci (CoNS) frequently causes late-onset sepsis in preterm infants. Vancomycin is the first-line therapy, but the emergence of reduced vancomycin-susceptibility strains has resulted in linezolid use, of which long-term safety in preterm infants is unknown.

OBJECTIVE

Evaluate the association between linezolid exposure and neurodevelopmental impairment (NDI) or death at 18-21 months of corrected age, in preterm infants with CoNS sepsis.

METHODS

Multicentric retrospective cohort study comparing long-term outcomes of preterm infants exposed to linezolid versus other antistaphylococcal antimicrobials. We included infants ≤28 weeks' gestational age (GA), with CoNS sepsis, admitted between January 2011 and June 2015 in 3 level-3 Canadian NICUs. Primary outcome was a composite of death or significant NDI (sNDI) at 18-21 months of corrected age. Secondary outcomes included NDI and individual components of the primary outcome. We assessed the relationship between linezolid exposure and outcomes using a multivariable logistic regression.

RESULTS

Of 274 infants included, 67 (24.4%) were exposed to linezolid. Median GA was 26 weeks and clinical characteristics were similar between groups. There was no difference in composite outcome of death or sNDI among the infants of both groups, but significantly more death by 18-21 months in the linezolid group (29.9% vs. 17.6%; P = 0.01).

CONCLUSIONS

Linezolid exposure was not associated with composite outcome of death or sNDI at 18-21 months. The association between linezolid and death may be due to indication bias. Further studies are warranted.

The risk factors of linezolid-induced lactic acidosis: A case report and review

BACKGROUND

In recent years, linezolid is increasingly used in multidrug-resistant bacteria therapy. At the same time, linezolid-induced lactic acidosis has been continually reported as a serious side effect. Notably, to our knowledge, there are limited available literatures that evaluate risk factors for linezolid-induced lactic acidosis, and there is no highly reliable study on the relationship between linezolid-induced lactic acidosis and age or gender. However, clinicians need relevant information to advice on the use of linezolid. Therefore, we report on a case of life-threatening lactic acidosis after 3 doses of linezolid exposure and evaluate the risk factors of linezolid-induced lactic acidosis.

METHODS

Cases of linezolid-induced lactic acidosis reported in PubMed were searched. Several characteristics and data of case numbers and deaths were extracted for analysis.

RESULTS

A total of 35 articles including 47 cases were included in this study. Twelve patients (25.5%) died due to linezolid-induced lactic acidosis. At the cut-offs of 7, 14, and 28 days, the mortalities were 27.3%, 20%, and 27.3%. No statistically significant difference was observed according to age and gender. However, the proportion (27.7% and 29.8%) and mortality (30.8% and 35.7%) of male patients were much higher than females in both ≥65 and <65 years old groups (proportion: 15.2% and 23.9%; mortality: 14.3% and 18.2%).

CONCLUSION

The mortality of linezolid-induced lactic acidosis was relatively high. The duration of linezolid use and age might not be risk factors. Gender (specifically, male) might be related to the mortality of linezolid-induced lactic acidosis.

Influence of Mitochondrial Genetics on the Mitochondrial Toxicity of Linezolid in Blood Cells and Skin Nerve Fibers

The antibiotic linezolid is a ribosomal inhibitor with excellent efficacy. Although the administration period has been reduced to 28 days, side effects, usually of hematologic or neuropathic origin, are still reported due to secondary inhibition of mitochondrial protein synthesis. Susceptibility to linezolid toxicity remains unknown. Therefore, the objective of this study was to gain an understanding of clinical heterogeneity in response to identical linezolid exposures through exhaustive examination of the molecular basis of tissue-dependent mitotoxicity, consequent cell dysfunction, and the association of mitochondrial genetics with adverse effects of linezolid administered for the recommended period. Peripheral blood mononuclear cells (PBMC) and skin nerve fibers from 19 and 6 patients, respectively, were evaluated before and after a 28-day linezolid treatment in order to assess toxic effects on mitochondria and cells. Mitochondrial DNA haplotypes and single nucleotide polymorphisms (SNPs) in ribosomal sequences where linezolid binds to mitochondrial ribosomes were also analyzed to investigate their genetic contributions. We found that linezolid reduced mitochondrial protein levels, complex IV activity, and mitochondrial mass in PBMC and was associated with a trend toward an increase in the rate of apoptosis. In skin tissue, mitochondrial mass increased within nerve fibers, accompanied by subclinical axonal swelling. Mitochondrial haplogroup U, mutations in 12S rRNA, and the m.2706A→G, m.3197T→C, and m.3010G→A polymorphisms in 16S rRNA showed a trend toward an association with increased mitochondrial and clinical adverse effects. We conclude that even when linezolid is administered for a shorter time than formerly, adverse effects are reported by 63% of patients. Linezolid exerts tissue-dependent mitotoxicity that is responsible for downstream cellular consequences (blood cell death and nerve fiber swelling), leading to adverse hematologic and peripheral nervous side effects. Multicentric studies should confirm genetic susceptibility in larger cohorts.

Double Peripheral Venous and Arterial Cannulation for Extracorporeal Membrane Oxygenation in Combined Septic and Cardiogenic Shock

BACKGROUND The use of venoarterial extracorporeal membrane oxygenation (va-ECMO) via peripheral cannulation for septic shock is limited by blood flow and increased afterload for the left ventricle. CASE REPORT A 15-year-old girl with acute myelogenous leukemia, suffering from severe septic and cardiogenic shock, was treated by venoarterial extracorporeal membrane oxygenation (va-ECMO). Sufficient extracorporeal blood flow matching the required oxygen demand could only be achieved by peripheral cannulation of both femoral arteries. Venous drainage was performed with a bicaval cannula inserted via the left V. femoralis. To accomplish left ventricular unloading, an additional drainage cannula was placed in the left atrium via percutaneous atrioseptostomy (va-va-ECMO). Cardiac function recovered and the girl was weaned from the ECMO on day 6. Successful allogenic stem cell transplantation took place 2 months later. CONCLUSIONS In patients with vasoplegic septic shock and impaired cardiac contractility, double peripheral venoarterial extracorporeal membrane oxygenation (va-va-ECMO) with transseptal left atrial venting can by a lifesaving option.

Linezolid-induced lactic acidosis: the thin line between bacterial and mitochondrial ribosomes

INTRODUCTION

Linezolid inhibits bacterial growth by targeting bacterial ribosomes and by interfering with bacterial protein synthesis. Lactic acidosis is a rare, but potentially lethal, side effect of linezolid. Areas covered: The pathogenesis of linezolid-induced lactic acidosis is reviewed with special emphasis on aspects relevant to the recognition, prevention and treatment of the syndrome. Expert opinion: Linezolid-induced lactic acidosis reflects the untoward interaction between the drug and mitochondrial ribosomes. The inhibition of mitochondrial protein synthesis diminishes the respiratory chain enzyme content and thus limits aerobic energy production. As a result, anaerobic glycolysis and lactate generation accelerate independently from tissue hypoxia. In the absence of any confirmatory test, linezolid-induced lactic acidosis should be suspected only after exclusion of other, more common, causes of lactic acidosis such as hypoxemia, anemia or low cardiac output. Normal-to-high whole-body oxygen delivery, high venous oxygen saturation and lack of response to interventions that effectively increase tissue oxygen provision all suggest a primary defect in oxygen use at the mitochondrial level. During prolonged therapy with linezolid, blood drug and lactate levels should be regularly monitored. The current standard-of-care treatment of linezolid-induced lactic acidosis consists of drug withdrawal to reverse mitochondrial intoxication and intercurrent life support.

Lactic Acidosis Induced by Linezolid Mimics Symptoms of an Acute Intracranial Bleed: A Case Report and Literature Review

Lactic acidosis is common and most often associated with disturbed acid-base balance. Rarely, it can be a life-threatening medication side effect. Hence, determining the etiology of lactic acidosis early in patients is paramount in choosing the correct therapeutic intervention. Although lactic acidosis as an adverse drug reaction of linezolid is a well-recognized and documented clinical entity, the occurrence of such mimicking an acute intracranial bleed has not been reported to our knowledge. The following case is presented as an example of such an occurrence. A 67-year-old woman presented to the emergency department for lethargy, nausea and syncope. The head CT did not demonstrate any bleeding or mass effect, but lab results were significant for elevated lactic acid. The patient recently underwent left total hip replacement surgery, which was complicated by a methicillin-resistant Staphylococcus aureus (MRSA) infection. She received 6 weeks of oral linezolid therapy. And upon learning that key part of her history, the linezolid was discontinued. Her lactic acid rapidly normalized and she was discharged home. Several publications demonstrate that linezolid induces lactic acidosis by disrupting crucial mitochondrial functions. It is essential that clinicians are aware that linezolid can cause lactic acidosis. And, the important reminder is that adverse drug reactions can often mimic common diseases. If it is not recognized early, ominous clinical consequences may occur. In conclusion, linezolid should be suspected and included in the differential diagnosis if lactic acidosis exists with an uncommon clinical picture.

Adverse effects of oral second-line antituberculosis drugs in children

INTRODUCTION

Increasing numbers of children with drug-resistant tuberculosis are accessing second-line antituberculosis drugs; these are more toxic than first-line drugs. Little is known about the safety of new antituberculosis drugs in children. Knowledge of adverse effects, and how to assess and manage these, is important to ensure good adherence and treatment outcomes.

AREAS COVERED

A Pubmed search was performed to identify articles addressing adverse effects of second-line antituberculosis drugs; a general search was done for the new drugs delamanid and bedaquiline. This review discusses adverse effects associated with oral second-line antituberculosis drugs. The spectrum of adverse effects caused by antituberculosis drugs is wide; the majority are mild or moderate, but these are important to manage as it could lead to non-adherence to treatment. Adverse effects may be more common in HIV-infected than in HIV-uninfected children.

EXPERT OPINION

Although children may experience fewer adverse effects from oral second-line antituberculosis drugs than adults, evidence from prospective studies of the incidence of adverse events in children is limited. Higher doses of second-line drugs, new antituberculosis drugs, and new drug regimens are being evaluated in children: these call for strict pharmacovigilance in children treated in the near future, as adverse effect profiles may change.

Drugs influencing acid base balance and bicarbonate concentration readings

Serum bicarbonate dosage is sensitive to pharmacological interferences. However, elevated bicarbonate concentration reflects chronic hypoventilation and has been proposed as a simple marker for screening patients with Obesity Hypoventilation Syndrome (OHS), a currently underdiagnosed multimorbid and high mortality disease. We provide a practical overview of the different drugs acting on the acid-base equilibrium to aid clinicians to interpret bicarbonate concentration readings. Little is known about the chronic impact of the usual doses of these drugs on serum bicarbonate concentration and further studies are needed. It is essential to take into account drugs that could interfere with this parameter to avoid misinterpretation of serum bicarbonate levels.

Antiproliferative activity of a series of 5‑(1H‑1,2,3‑triazolyl) methyl‑ and 5‑acetamidomethyl‑oxazolidinone derivatives

In the face of increasing resistance to the existing antibiotics, oxazolidinones (exemplified by linezolid) have been developed as promising antibacterial agents, but may have other useful actions. In the present study, a series of 5‑(1H‑1,2,3‑triazoly) l‑methyl‑, 5‑acetamidomethyl‑morpholino and N‑substituted‑piperazino oxazolidinone derivatives were investigated to determine whether they are active against eukaryotic cells. An MTT assay, validated by cell counting, was used to assess the effect of nine oxazolidinone derivatives (concentrations 100 nM‑10 µM) on the proliferation of MCF7 human breast cancer cells. The three most active compounds were then tested on MDA231 breast cancer cells. Cytotoxicity of the selected derivatives was determined by assessing the extent of apoptosis by flow cytometry. The antimetastatic potential of these compounds was assessed on MDA231 cells using wound healing and agarose invasion assays. The 5‑triazolylmethyl piperazino‑oxazolidinone derivatives containing 4‑N‑(2‑chlorocinnamoyl), 4‑N‑(4‑nitrobenzoyl) and 4‑N‑methylsulfonyl moieties exhibited the most potent cytostatic activity against cancer, inhibiting proliferation by up to 70%, in the same order as their reported antibacterial activity against Staphylococcus aureus, but at higher concentrations. Unexpectedly, several derivatives stimulated proliferation at 100 nM, well below their antibacterial minimum inhibitory concentrations. Certain compounds also retarded the motility and invasion of MDA231 cells. Three of the tested derivatives had no effect on the eukaryotic cell lines, demonstrating their preferential activity against bacteria. Two compounds actually stimulated eukaryotic cell proliferation. The remaining three exhibited potent cytostatic activity against and cancer cells, displaying differences in response at low and high concentrations, which may suggest multiple targets on eukaryotic cells. These latter compounds may be useful as anticancer agents.

Safety and tolerability profile of second-line anti-tuberculosis medications

Tuberculosis (TB) remains a major public health problem, representing the second leading cause of death from infectious diseases globally, despite being nearly 100 % curable. Multidrug-resistant (MDR)-TB, a form of TB resistant to isoniazid and rifampicin (rifampin), two of the key first-line TB drugs, is becoming increasingly common. MDR-TB is treated with a combination of drugs that are less effective but more toxic than isoniazid and rifampicin. These drugs include fluoroquinolones, aminoglycosides, ethionamide, cycloserine, aminosalicyclic acid, linezolid and clofazimine among others. Minor adverse effects are quite common and they can be easily managed with symptomatic treatment. However, some adverse effects can be life-threatening, e.g. nephrotoxicity due to aminoglycosides, cardiotoxicity due to fluoroquinolones, gastrointestinal toxicity due to ethionamide or para-aminosalicylic acid, central nervous system toxicity due to cycloserine, etc. Baseline evaluation may help to identify patients who are at increased risk for adverse effects. Regular clinical and laboratory evaluation during treatment is very important to prevent adverse effects from becoming serious. Timely and intensive monitoring for, and management of adverse effects caused by, second-line drugs are essential components of drug-resistant TB control programmes; poor management of adverse effects increases the risk of non-adherence or irregular adherence to treatment, and may result in death or permanent morbidity. Treating physicians should have a thorough knowledge of the adverse effects associated with the use of second-line anti-TB drugs, and routinely monitor the occurrence of adverse drug reactions. In this review, we have compiled safety and tolerability information regarding second-line anti-TB drugs in both adults and children.

A triad of linezolid toxicity: hypoglycemia, lactic acidosis, and acute pancreatitis

We present a case of suspected linezolid toxicity in a 34-year-old man with sickle cell disease and line-related vancomycin-resistant enterococcal bacteremia and tricuspid valve endocarditis. The patient developed sudden-onset hypoglycemia, lactic acidosis, and acute pancreatitis 11 days after initiation of linezolid. All adverse effects quickly resolved with drug cessation. The pathophysiology underlying this triad of linezolid toxicity is unclear, but may be related to mitochondrial dysfunction.

Drug-induced acid-base disorders

The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

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.

Pharmacokinetics of linezolid treatment using intravenous and oral administrations in extremely premature infants

INTRODUCTION

Vancomycin is the usual antibiotic treatment in coagulase-negative staphylococcus sepsis in premature infants but causes renal toxicity. As linezolid is effective in Gram-positive cocci infection, and devoid of renal side-effects, it has been used in Nantes neonatal intensive care units and linezolid plasma concentrations were monitored.

AIM

The aims of this study are to report data on linezolid concentrations in premature infants, describe clinical and bacteriological evolution during treatment, and determine potential side effects.

METHODS

A retrospective observational study of premature infants treated with linezolid in Nantes Hospital from January 2008 through November 2011 was conducted. Linezolid plasma concentrations, possible side effects due to linezolid, and clinical response to linezolid treatment were collected from folder review.

RESULTS

Twenty-four linezolid plasma concentrations were monitored in 16 premature patients, at steady state for continuous intravenous administration or 7 ± 1.5 h after last oral administration. Except for one case, linezolid plasma concentrations were ≥minimal inhibition concentration (MIC) for linezolid for both parenteral and oral administrations. We observed three cases of thrombocytopenia, two of leukopenia, three of neutropenia, and one of severe hyperlactacidemia, resolving after discontinuation of treatment. Clinical signs of infection resolved in 13/16 cases. Bacteria were coagulase-negative Staphylococci in 12/16 cases and were eradicated in 9/12 evaluable cases.

CONCLUSIONS

This study reports an adequate linezolid plasma concentration with regard to the linezolid MIC in extremely premature infants. However, considering adverse events reported, its use should be cautious and may concern only oral administration during the late phase of infection, to limit paradoxical catheter use to treat nosocomial infections. Moreover, safe and efficient anti-Staphylococcus therapies should be identified to treat this vulnerable population.

Pharmacokinetics of tedizolid in subjects with renal or hepatic impairment

Two open-label, single-dose, parallel-group studies were conducted to characterize the pharmacokinetics of the novel antibacterial tedizolid and the safety of tedizolid phosphate, its prodrug, in renally or hepatically impaired subjects. Tedizolid pharmacokinetics in subjects with severe renal impairment without dialysis support was compared with that of matched control subjects with normal renal function. Effects of hemodialysis on tedizolid pharmacokinetics were determined in a separate cohort of subjects undergoing long-term hemodialysis. Effects of hepatic impairment on tedizolid pharmacokinetics were determined in subjects with moderate or severe hepatic impairment and compared with those of matched control subjects with normal hepatic function. Each participant received a single oral (hepatic impairment) or intravenous (renal impairment) dose of tedizolid phosphate at 200 mg; hemodialysis subjects received two doses (separated by 7 days), before and after dialysis, in a crossover fashion. The pharmacokinetics of tedizolid was similar in subjects with severe renal impairment and controls (∼8% lower area under the concentration-time curve [AUC], with a nearly identical peak concentration) and in subjects undergoing hemodialysis before and after tedizolid phosphate administration (∼9% lower AUC, with a 15% higher peak concentration); <10% of the dose was removed during 4 h of hemodialysis. Tedizolid pharmacokinetics was only minimally altered in subjects with moderate or severe hepatic impairment; the AUC was increased approximately 22% and 34%, respectively, compared with that of subjects in the control group. Tedizolid phosphate was generally well tolerated in all participants. These results suggest that tedizolid phosphate dose adjustments are not necessary in patients with any degree of renal or hepatic impairment. (This study has been registered at ClinicalTrials.gov under registration numbers NCT01452828 [renal study] and NCT01431833 [hepatic study].).

Early lactic acidosis associated with linezolid therapy in paediatric patients

Linezolid, an oxazolidinone class antibiotic, is used to treat Gram-positive infections, including those due to meticillin-resistant staphylococci and vancomycin-resistant enterococci. In paediatric clinical trials, the frequency of possible linezolid-related adverse events ranged from 18.8% to 25.6%. The most commonly reported side effects are gastrointestinal disturbances, headache, rash and liver function alterations. Lactic acidosis has been reported as a side effect of linezolid treatment, and limited data suggest it may be more common in children. We report on our experience of treating 50 children aged 1 month to years with linezolid. Eight patients (16%) developed lactic acidosis and another eight (16%) had lactic acidaemia without acidosis. Onset of lactic acidaemia (median 1.5 days; range 1-72 days) and lactic acidosis (median 2 days; range 1-13 days) tended to be early. Being an ICU patient and requiring mechanical ventilation significantly increased the risk of lactic acidaemia or acidosis (OR=22.75, 95% CI 4.24-122.09; OR=32.67, 95% CI 5.83-183.19, respectively; P<0.001). All 16 patients were able to continue linezolid treatment. Linezolid therapy was effective (microbiologic and/or clinical cure) in 39 patients (78%). Nine patients died whilst receiving linezolid treatment; the deaths were not considered to be a result of linezolid treatment failure. Two patients who did not respond clinically to linezolid recovered after their treatment was changed to vancomycin. Linezolid use in children appears to be as safe and effective as in adults. However, lactic acidosis appears to be more common, and occur earlier, in children.

Emergence of multiresistant methicillin-resistant Staphylococcus aureus in two patients with atopic dermatitis requiring linezolid treatment

We report two patients with atopic dermatitis who developed methicillin-resistant Staphylococcus aureus (MRSA) skin infections resistant to clindamycin and trimethoprim-sulfamethoxazole requiring repeated linezolid treatment. For one patient and family members who received an aggressive regimen of staphylococcal decolonization, including intranasal mupirocin, dilute bleach baths, and bleach cleansing of household items and surfaces, subsequent culture results demonstrated methicillin-susceptible S. aureus colonization and infection. These findings underscore the challenges presented by multiresistant MRSA infections in children with atopic dermatitis.

Linezolid use in hospitalized children

We used the Pediatric Health Information System to evaluate linezolid use among hospitalized children. From 2003 to 2007, use increased 5-fold, including wide interhospital variation, then stabilized through 2011. Linezolid was responsible for 3% of total antibiotic expenditures. Children with respiratory, oncologic or transplant conditions were the most frequently treated with linezolid.

Nocardiosis in transplant recipients

Nocardiosis is a rare opportunistic infection caused by Nocardia spp., an aerobic actinomycete, that mainly affects patients with cell-mediated immunity defects, such as transplant recipients. Despite recent progress regarding Nocardia identification and changes in taxonomic assignment, many challenges remain for the diagnosis or management of nocardiosis. This opportunistic infection affects 0.04 to 3.5 % of patients with solid organ or hematopoietic stem cell transplantation, depending on the organ transplanted, cytomegalovirus (CMV) infection, corticosteroids dose and calcineurin inhibitors level. Nocardiosis diagnosis relies on appropriate clinical, radiological and microbiological workup that includes the sampling of an accessible involved site and molecular microbiology tools. In parallel, extensive clinical and radiological evaluations are mandatory, including brain imaging, even in the absence of neurological signs. In transplanted patients, differential diagnosis is challenging, with co-infections reported in 20 to 64 % of cases. As the antibiotic susceptibility pattern varies among species, the antimicrobial regimen before species identification should rely on the association of antibiotics active on all species of Nocardia. Bactericidal antibiotics are required in cases of severe or disseminated disease. Furthermore, in transplant recipients, combination therapy is difficult to manage because of cumulative toxicity and interactions with immunosuppressive agents. Because of a high recurrence rate, antibiotic therapy should be prescribed for 6 to 12 months.

Clinical update on linezolid in the treatment of Gram-positive bacterial infections

Gram-positive pathogens are a significant cause of morbidity and mortality in both community and health care settings. Glycopeptides have traditionally been the antibiotics of choice for multiresistant Gram-positive pathogens but there are problems with their use, including the emergence of glycopeptide-resistant strains, tissue penetration, and achieving and monitoring adequate serum levels. Newer antibiotics such as linezolid, a synthetic oxazolidinone, are available for the treatment of resistant Gram-positive bacteria. Linezolid is active against a wide range of Gram-positive bacteria and has been generally available for the treatment of Gram-positive infections since 2000. There are potential problems with linezolid use, including its bacteriostatic action and the relatively high incidence of reported adverse effects, particularly with long-term use. Long-term use may also be complicated by the development of resistance. However, linezolid has been shown to be clinically useful in the treatment of several serious infections where traditionally bacteriocidal agents have been required and many of its adverse effects are reversible on cessation. It has also been shown to be a cost-effective treatment option in several studies, with its high oral bioavailability allowing an early change from intravenous to oral formulations with consequent earlier patient discharge and lower inpatient costs.