Serotonin Toxicity Associated with Concomitant Use of Linezolid

Antiepileptic drugs and serotonin syndrome- A systematic review of case series and case reports

Serotonin syndrome (SS) is a drug‑induced, potentially fatal, clinical syndrome resulting from drugs that have serotonergic properties. Several antiepileptic drugs (AEDs) are known to have serotonergic properties and it can be hypothesized that such AEDs can cause SS. This study aims to review the literature on SS in patients receiving AEDs. We performed a systematic review of Scopus and MEDLINE/PUBMED for case reports and case series of SS where patients had received at least one AED at the onset of symptoms. The cases published in the English literature between 1 January 1991 and 1 April 2021 were included. Initial search identified 1263 articles of which 63 (76 patients) were included in the final analysis. Most of the included cases (53 cases, 70%) have been published in the last 10 years. The mean age of the 76 patients was 40.6 ± 17.8 years, and 51% of cases were females. These patients had been exposed to a total of 8 different types of AEDs. Valproic acid was the most common drug (29, 38%), followed by lamotrigine (22, 29%), gabapentin (16, 21%), pregabalin (seven, 9%), topiramate (five, 7%) and carbamazepine (two, 3%). There has been one case each with phenytoin and oxcarbazepine. Seven (9%) patients received more than one AEDs. Most patients (67, 88%) also received other serotoninergic agents. Only nine (12%) patients were on AEDs alone. The most common clinical condition for using AEDs was psychiatric disorders (36 patients, 47.3%), followed by migraine (17, 22.4%), other painful conditions (15, 19.7%), epilepsy (7, 9.2%), and perioperative conditions (8, 10.5%). Death was reported in two patients. We suggest that AEDs, because of their serotonergic properties, may induce SS, especially in patients who are on another serotonergic agent.

Reported Cases of Serotonin Syndrome in MDMA Users in FAERS Database

3,4-Methylenedioxymethamphetamine (MDMA), is investigated as a treatment for post-traumatic stress disorder and other anxiety-related conditions in multiple placebo-controlled and open label studies. MDMA-assisted therapy is projected for approval by the United States Food and Drug Administration (FDA) and other regulatory agencies worldwide within the next few years. MDMA is a monoamine releaser and uptake inhibitor affecting serotonin, potentially increasing the risk of serotonin syndrome (SS). No instances of SS have occurred in clinical trials. The relatively small number of patients in controlled trials warranted a survey of FDA Adverse Event Reporting System data for the occurrence of SS in a larger database. We found 20 SS cases in people exposed to MDMA, all of which had also taken one or more substances with serotonergic properties in addition to MDMA, including amphetamines, stimulants, and opioids. There were no cases of SS associated with MDMA where MDMA was the sole reported compound taken.

Linezolid-induced serotonin syndrome

Linezolid is an oxazolidinone antibiotic, which is a weak, reversible, nonselective monoamine oxidase A and B inhibitor; is known to increase serotonin levels, and has been implicated in the development of serotonin syndrome (SS). There is limited literature on the development of SS with linezolid, when used alone. In this report, we present the case of a 70-year-old female who developed features of SS while being treated with linezolid 600 mg twice daily for pneumonia. The SS in her case was managed with stoppage of linezolid, administration of cyproheptadine, and supportive measures.

Neurological and Psychiatric Adverse Effects of Antimicrobials

Antimicrobials are a widely used class of medications, but several of them are associated with neurological and psychiatric side effects. The exact incidence of neurotoxicity with anti-infectives is unknown, although it is estimated to be < 1%. Neurotoxicity occurs with all classes of antimicrobials, such as antibiotics, antimycobacterials, antivirals, antifungals and antiretrovirals, with side effects ranging from headaches, anxiety and depression to confusion, delirium, psychosis, mania and seizures, among others. It is important to consider these possible side effects to prevent misdiagnosis or delayed treatment as drug withdrawal can be associated with reversibility in most cases. This article highlights the different neurotoxic effects of a range of antimicrobials, discusses proposed mechanisms of onset and offers general management recommendations. The effects of antibiotics on the gut microbiome and how they may ultimately affect cognition is also briefly examined.

Clinically Significant Drug-Drug Interactions Involving Medications Used for Symptom Control in Patients With Advanced Malignant Disease: A Systematic Review

CONTEXT

Most patients with advanced malignant disease need to take several drugs to control symptoms. This treatment raises risks of serious adverse effects and drug-drug interactions (DDIs).

OBJECTIVES

To identify studies reporting clinically significant DDIs involving medications used for symptom control, other than opioids used for pain management, in adult patients with advanced malignant disease.

METHODS

Systematic review with searches in Embase, MEDLINE, and the Cochrane Central Register of Controlled Trials, from the start of the databases (Embase from 1980) through June 21, 2018. In addition, reference lists of relevant full-text articles were hand-searched.

RESULTS

Of 9699 retrieved citations, 462 were considered potentially eligible. After full-text reading, 29 were included in the final analysis, together with 13 articles from reference lists. The 42 included publications were case reports, letters to the Editor, and one retrospective study. Drugs most often involved were antiepileptics, antidepressants, corticosteroids, and nonopioid analgesics. Clinical manifestations of identified DDIs included sedation, respiratory depression, serotonin syndrome, neuroleptic malignant syndrome, delirium, seizures, ataxia, liver and kidney failure, bleeding, cardiac arrhythmias, rhabdomyolysis, and others. The most common mechanisms eliciting DDIs were alteration of CYP450-dependent metabolism and overstimulation of serotonin receptors in the central nervous system.

CONCLUSION

Drugs used for symptom control in patients with advanced cancer may cause serious DDIs. Although there is limited evidence for the risk of clinically significant DDIs, physicians treating patients with cancer should try to limit polypharmacy, avoid drug combinations with a high risk of DDIs, and closely monitor patients for adverse drug reactions.

Management of severe arterial hypertension associated with serotonin syndrome: a case report analysis based on systematic review techniques

Serotonin syndrome is thought to arise from serotonin excess. In many cases, symptoms are mild and self-limiting. But serotonin syndrome can become life threatening, when neuromuscular hyperexcitability spins out of control. Uncontainable neuromuscular hyperexcitability may lead to cardiovascular complications, linked to extreme changes in blood pressure. Currently, there is little guidance on how to control blood pressure in hyperserotonergic states. We report a case with treatment-resistant arterial hypertension, followed by a clinical review (using systematic review principles and techniques) of the available evidence from case reports published between 2004 and 2016 to identify measures to control arterial hypertension associated with serotonin syndrome. We conclude that classic antihypertensives may not be effective for the treatment of severe hypertension associated with serotonin syndrome. Benzodiazepines may lower blood pressure. Patients with severe hypertension not responding to benzodiazepines may benefit from cyproheptadine, propofol or both. In severe cases, higher cyproheptadine doses than currently recommended may be necessary.

LInezolid for the Treatment of Nocardia spp. Infections

Objective:

To review the available evidence regarding the use of linezolid for the treatment of Nocardia spp. infections.

Data Sources:

Data were identified through a search of MEDLINE (1966-May 2007), American Search Premier (1975-May 2007), International Pharmaceutical Abstracts (1960-2007), Science Citation Index Expanded (1996-2007), and Cochrane Databases (publications archived until May 2007) using the terms linezolid and Nocardia.

Study Selection and Data Extraction:

Prospective and retrospective studies, case reports, case series, and in vitro studies were eligible for inclusion if they used linezolid for nocardiosis regardless of site of infection and outcome.

Data Synthesis:

We identified 11 published cases of linezolid use for Nocardia spp. infections. The predominant species isolated were N. asteroides (n=4; 36%) and N. farcinica (n= 3; 27%). Nocardiosis with central nervous system involvement (n= 7; 64%) or disseminated disease (n= 4; 36%) were most common. The main reason for discontinuation of previous antimicrobials was most often related to adverse effects (n= 5; 45%), followed by clinical failure (n = 3; 27%). Linezolid was associated with cure or improvement in all cases (n =11; 100%). However, the majority of patients developed serious complications that may have led to premature discontinuation of therapy with linezolid, including myelosuppression (n = 5; 45%) or possible/confirmed peripheral neuropathy (n = 2; 18%).

Conclusions:

The limited published data suggest that linezolid appears to be an effective alternative to trimethoprim/sulfamethoxazole for the treatment of nocardiosis. Unfortunately, the high cost and potentially serious long-term toxicities of linezolid appear to limit its use and relegate it to salvage therapy alone or in combination with other antimicrobials.

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

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

Treatment of infections due to resistant Staphylococcus aureus

This chapter reviews data on the treatment of infections caused by drug-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). This review covers findings reported in the English language medical literature up to January of 2013. Despite the emergence of resistant and multidrug-resistant S. aureus, we have seven effective drugs in clinical use for which little resistance has been observed: vancomycin, quinupristin-dalfopristin, linezolid, tigecycline, telavancin, ceftaroline, and daptomycin. However, vancomycin is less effective for infections with MRSA isolates that have a higher MIC within the susceptible range. Linezolid is probably the drug of choice for the treatment of complicated MRSA skin and soft tissue infections (SSTIs); whether it is drug of choice in pneumonia remains debatable. Daptomycin has shown to be non-inferior to either vancomycin or β-lactams in the treatment of staphylococcal SSTIs, bacteremia, and right-sided endocarditis. Tigecycline was also non-inferior to comparator drugs in the treatment of SSTIs, but there is controversy about whether it is less effective than other therapeutic options in the treatment of more serious infections. Telavancin has been shown to be non-inferior to vancomycin in the treatment of SSTIs and pneumonia, but has greater nephrotoxicity. Ceftaroline is a broad-spectrum cephalosporin with activity against MRSA; it is non-inferior to vancomycin in the treatment of SSTIs. Clindamycin, trimethoprim-sulfamethoxazole, doxycycline, rifampin, moxifloxacin, and minocycline are oral anti-staphylococcal agents that may have utility in the treatment of SSTIs and osteomyelitis, but the clinical data for their efficacy is limited. There are also several drugs with broad-spectrum activity against Gm-positive organisms that have reached the phase II and III stages of clinical testing that will hopefully be approved for clinical use in the upcoming years: oritavancin, dalbavancin, omadacycline, tedizolid, delafloxacin, and JNJ-Q2. Thus, there are currently many effective drugs to treat resistant S. aureus infections and many promising agents in the pipeline. Nevertheless, S. aureus remains a formidable adversary, and despite our deep bullpen of potential therapies, there are still frequent treatment failures and unfortunate clinical outcomes. The following discussion summarizes the clinical challenges presented by MRSA, the clinical experience with our current anti-MRSA antibiotics, and the gaps in our knowledge on how to use these agents to most effectively combat MRSA infections.

Comparative evaluation of serotonin toxicity among veterans affairs patients receiving linezolid and vancomycin

Despite the theoretical risk of serotonin toxicity (ST) with linezolid, "real-world" clinical evaluations of the risk of ST in patients receiving linezolid have been limited to case reports and noncomparator studies. An observational, matched-cohort study was conducted to evaluate the risk of ST among hospitalized patients who received linezolid or vancomycin at the Upstate New York Veterans Affairs Healthcare Network (Veterans Integrated Service Network 2 [VISN-2]). Matching criteria included VISN-2 hospital, hospital ward, prior hospital length of stay, age, and baseline platelet counts. The patients' electronic medical records were evaluated for symptoms consistent with ST and the Hunter serotonin toxicity criteria (HSTC) using an intensive, natural word search algorithm. The study included 251 matched pairs. Demographics and comorbidities were similar between groups. Over half of the study population received at least one concurrent medication with serotonergic activity. Receipt of agents with serotonergic activity was more pronounced in the vancomycin group, and the higher frequency was due to concomitant antihistamine and antiemetic use. Antidepressant use, including selective serotonin reuptake inhibitors (SSRIs), was similar between groups. No patients in either group were found to meet the criteria using the word search algorithm for ST. Fewer linezolid patients than vancomycin patients met the HSTC overall (3.2% versus 8.8%) and when stratified by receipt of a concurrent serotonergic agent (4.3% versus 12.4%). Of the patients meeting the HSTC, most had past or present comorbidities that may have contributed to or overlapped the HSTC. This study of hospitalized patients revealed comparably low frequencies of adverse events potentially related to ST among patients who received linezolid or vancomycin.

Linezolid-induced near-fatal serotonin syndrome during escitalopram therapy: case report and review of literature

Linezolid is a synthetic antimicrobial agent of the oxazolidinone class with weak, nonspecific inhibitor of monoamine oxidase enzymes. Concomitant therapy with an adrenergic or serotonergic agent or consuming tyramine (>100 mg/day) may induce serotonin syndrome (SS). We present a case report of near-fatal adverse interaction between linezolid and escitalopram inducing SS in a 65-year-old woman with sepsis, under empirical antibiotic treatment. This report also summarizes the current relevant literature as identified via PubMed, EMBASE, and PsycINFO, supplemented with a manual search of cross references.

A review of the interplay between tuberculosis and mental health

AIMS

Tuberculosis and mental illness share common risk factors including homelessness, HIV positive serology, alcohol/substance abuse and migrant status leading to frequent comorbidity. We sought to generate a comprehensive literature review that examines the complex relationship between tuberculosis and mental illness.

METHODS

A literature search was conducted in MedLine, Ovid and Psychinfo, with further examination of the references of these articles. In total 316 articles were identified. It was not possible to conduct a formal meta-analysis due to the absence of randomised controlled data.

RESULTS

Rates of mental illness of up to 70% have been identified in tuberculosis patients. Medications used in the treatment of common mental illnesses, such as depression, may have significant interactions with anti-tuberculosis agents, especially isoniazid and increasingly linezolid. Many medications used in the treatment of tuberculosis can have significant adverse psychiatric effects and some medications such as rifampicin may reduce the effective doses of anti-psychotics y their enzyme induction actions. Treatment with agents such as cycloserine has been associated with depression, and there have been reported cases of psychosis with most anti-tuberculous agents. Mental illness and substance abuse may also affect compliance with treatment, with attendant public health concerns.

CONCLUSIONS

As a result of the common co-morbidity of mental illness and tuberculosis, it is probable that physicians will encounter previously undiagnosed mental illness among patients with tuberculosis. Similarly, psychiatrists are likely to meet tuberculosis among their patients. It is important that both psychiatrists and physicians are aware of the potential for interactions between the drugs used to treat tuberculosis and psychiatric conditions.

Serotonergic and Adrenergic Drug Interactions Associated with Linezolid: A Critical Review and Practical Management Approach

OBJECTIVE

To describe the evidence for serotonergic and adrenergic drug interactions with linezolid and discuss clinical management strategies.

DATA SOURCES

A literature search of PubMed (1947–November 2012), MEDLINE (1946–November 2012), EMBASE (1974–November 2012), and International Pharmaceutical Abstracts (1970–November 2012) was conducted using the terms linezolid, drug interaction, serotonin syndrome, serotonin toxicity, sympathomimetic, serotonergic agents, and adrenergic agents. Citations of retrieved articles were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

English-language articles describing coadministration of serotonergic or adrenergic agents with linezolid to humans were included. Studies published only in abstract form were excluded.

DATA SYNTHESIS

One prospective study, 6 retrospective studies, and 24 case reports were identified describing a serotonergic or adrenergic drug interaction. Incidence of serotonin syndrome in patients on linezolid and serotonergic agents ranged between 0.24% and 4%. Serotonergic agents determined to have probable (according to the Horn Drug Interaction Probability Scale) linezolid interactions in case reports included meperidine, citalopram, escitalopram, fluoxetine, paroxetine, sertraline, duloxetine, and venlafaxine. Serotonergic agent dose and duration of coadministration with linezolid did not appear to influence the occurrence of serotonin syndrome. Adrenergic medication coadministration was associated with a possible drug interaction as determined by the Horn Drug Interaction Probability Scale but did not appear to result in clinically significant drug interactions with linezolid.

CONCLUSIONS

Linezolid-associated serotonergic drug interactions occur more commonly than adrenergic interactions. Serotonergic interactions considered probable according to the Horn Drug Interaction Probability Scale do not appear to correlate with drug dosage; time of onset ranges from <1 to 20 days, and effect resolves in <1 to 5 days after discontinuation of offending agents. If coadministration of linezolid and a serotonergic agent cannot be avoided, clinicians should be aware of the symptoms and management of serotonergic toxicity; close monitoring is recommended and additional serotonergic agents should not be used. While adrenergic drug interactions with linezolid are less common in clinical practice, monitoring for signs of hypertension remains important.

Clinical relevance of linezolid-associated serotonin toxicity

OBJECTIVE

To evaluate and review the literature surrounding serotonin toxicity in patients receiving linezolid and determine the clinical relevance of this reaction.

DATA SOURCES

Literature was accessed via MEDLINE/PubMed and Google Scholar (both through February 2013) using the search terms linezolid, serotonin syndrome, serotonin toxicity, and adverse reaction.

STUDY SELECTION AND DATA EXTRACTION

Relevant case reports, retrospective studies, surveys, and review articles were included. Bibliographies of all relevant articles were reviewed for additional sources.

DATA SYNTHESIS

Linezolid exhibits mild, nonselective inhibition of monoamine oxidase and has been associated with serotonin toxicity when used in combination with other serotonergic agents. Based on published reports, the incidence of linezolid-associated serotonin toxicity is between 0.54% and 18.2%. Our review identified 32 documented cases, including 3 fatalities. Most cases occurred in patients concurrently receiving selective serotonin reuptake inhibitors. Receipt of multiple agents with serotonergic activity seems to increase the risk of serotonin toxicity. Both onset and resolution of symptoms varied from hours to days.

CONCLUSIONS

Current Food and Drug Administration recommendations to avoid the use of linezolid in patients receiving select serotonergic agents highlight the need to carefully balance the risk/benefit ratio in this situation. Although linezolid has been available for 12 years, reports of serotonin toxicity with this agent are uncommon. While clinicians should be aware of this potentially severe interaction and closely monitor patients who are receiving linezolid in combination with serotonergic agents, our findings show that linezolid is not contraindicated in this situation.

Linezolid is associated with serotonin syndrome in a patient receiving amitriptyline, and fentanyl: a case report and review of the literature

We report a unique case of an adverse interaction between the oxazolidinone antibiotic linezolid, the tricyclic antidepressant amitriptyline and the opioid analgesic fentanyl in a 68-year-old woman with advanced ischemic peripheral arterial disease and sepsis, under empirical antibiotic treatment. We also summarize the current relevant literature as identified via PubMed, EMBASE, and PsycINFO as well as reference sections of selected articles.

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.

The oxazolidinones: past, present, and future

The success of linezolid stimulated significant efforts to discover new agents in the oxazolidinone class. Over a dozen oxazolidinones have reached the clinic, but many were discontinued due to lack of differentiated potency, inadequate pharmacokinetics, and safety risks that included myelosuppression. Four oxazolidinones are currently undergoing clinical evaluation. The Trius Therapeutics compound tedizolid phosphate (formerly known as torezolid phosphate, TR-701, DA-7218), the most advanced, is in phase 3 clinical trials for acute bacterial skin and skin structure infections. Rib-X completed two phase 2 studies for radezolid (Rx-01_667, RX-1741) in uncomplicated skin and skin structure infections and community-acquired pneumonia. Pfizer and AstraZeneca have each identified antitubercular compounds that have completed phase 1 studies: sutezolid (PNU-100480, PF-02341272) and AZD5847 (AZD2563), respectively. The oxazolidinones share a relatively low frequency of resistance largely due to the requirement of mutations in 23S ribosomal RNA genes. However, maintaining potency against strains carrying the mobile cfr gene poses a challenge for the oxazolidinone class, as well as other 50S ribosome inhibitors that target the peptidyl transferase center.

Linezolid interaction with serotonin reuptake inhibitors: report of two cases and incidence assessment

BACKGROUND

Prompted by the advent of potentially life-threatening neuromuscular symptoms following initiation of linezolid therapy in two patients receiving treatment with a serotonin reuptake inhibitor antidepressant, an evaluation was conducted to determine the incidence and characteristics of symptomatic serotonin toxicity among hospitalized patients receiving combined treatment with these medications.

METHODS

Patients admitted between January 1, 2006 and August 30, 2008 who received linezolid concurrently with citalopram or escitalopram were identified and their medical records were examined. Patients were judged to have serotonin toxicity if their records contained documentation of clinical evidence adequate to fulfill requisites of the Hunter Serotonin Toxicity Criteria. Severity of serotonin-related symptoms was graded according to previously established criteria.

RESULTS

During the period of observation, 24 patients received concurrent treatment with linezolid and citalopram or escitalopram. Of these, one patient (4%) treated with citalopram met evidentiary requirements for diagnosis of serotonin toxicity. The severity of symptoms in this patient was graded as mild. No evidence of serious harm related to a possible drug interaction was identified.

CONCLUSIONS

Severe symptoms associated with serotonin toxicity were shown to be uncommon in patients receiving linezolid and selected serotonin reuptake inhibitors. Nonetheless, serious interaction-related toxicity has been observed at our institution and reported in detail by others. Accordingly, concurrent use of these medications is categorized as contraindicated. Alternative antimicrobial therapy should be instituted in most cases. If no suitable alternative is available, recipient patients should be hospitalized for expectant observation and rigorous monitoring.

[Perioperative adverse events related to antidepressive agents use]

OBJECTIVE

Depression is the most common psychiatric disease, which is treated by the use of antidepressive agents possessing various mechanisms of action. Thus, the use in preoperative period of antidepressive agents is frequent (7% of patients scheduled for surgery). The objective of this review was to update the knowledge on the drug interactions between antidepressive agents and drugs used in perioperative period.

METHODS

(i) Medline and Ovid databases using combination of antidepressive agent and perioperative period as keywords; (ii) national and European epidemiologic database; (iii) expert recommendation and official French health agency; (iv) reference book chapters.

RESULTS

The clinical practice showed a limited risk of adverse event related to antidepressant agents interaction with perioperative used drugs. In the two past decades, few relevant observations of adverse event related with imipramine and monoamine oxidase inhibitors use was reported. The most recent antidepressive agents had no serious adverse interaction. Nevertheless, the serotonin syndrome has to be known as far as it is more and more reported. In case of hypotension, the use of vasopressive agent has to be careful because of excessive response.

Pharmacological issues of linezolid: an updated critical review

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

Linezolid: a review of safety and tolerability

Linezolid has demonstrated activity against antibiotic-susceptible and antibiotic-resistant aerobic Gram-positive cocci. The availability of intravenous and oral formulations, with near 100% bioavailability of the latter, is hoped to facilitate the management of multiply drug-resistant Gram-positive infections. Linezolid was approved for clinical use in the United States in April 2000 and has subsequently been approved in other countries for the management of community-acquired and nosocomial pneumonia, complicated and uncomplicated skin and soft-tissue infections, and infections caused by methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, including cases with concurrent bacteremia. Additional studies have demonstrated potential use in febrile cancer patients with neutropenia, and case reports have documented some efficacy in the management of infective endocarditis, tuberculosis, nocardiosis, and in anaerobic infections. Given the potential for significantly increased use of linezolid, a thorough review and update of its tolerability and safety profile is warranted.

Serotonin toxicity as a consequence of linezolid use in revision hip arthroplasty

Linezolid is the first in a new group of antibiotics called oxazolidinones. As a potent antimicrobial, it has activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus, penicillin-resistant Streptococcus pneumoniae, and macrolide-resistant streptococci. There are several documented case reports of serotonin toxicity when used with selective serotonin reuptake inhibitors. The symptoms of serotonin syndrome are alteration of mental state, autonomic dysfunction, and neuromuscular disorders. This article presents a case of an interaction of the serotonin reuptake inhibitor venlafaxine and linezolid and the possible diagnostic problems that can occur. A 58-year-old woman presented with signs of systemic infection. Her medical history included bladder resection for transitional cell carcinoma, bilateral total hip arthroplasty (THA), and depression, for which she was on venlafaxine. Serological and imaging investigations revealed MRSA infection of the bilateral THA. The patient was started on vancomycin and rifampicin intravenously. As intravenous access was becoming problematic and long-term antibiotics were needed, treatment was changed to oral linezolid and oral rifampicin. Four days after the commencement of linezolid, the patient was acutely disorientated with generalized cerebellar signs and no autonomic dysfunction. A computed tomography scan of the head and lumbar puncture revealed no abnormal findings. A diagnosis of serotonin toxicity was made. The patient recovered when linezolid and venlafaxine were discontinued and supportive measures were provided. Linezolid is a popular choice of antibiotic, especially for the treatment of orthopedic-related MRSA infections. Patients who commonly require linezolid as an antimicrobial are those with complex infections where other antibiotic treatment has failed. It is therefore important to be vigilant with linezolid use. Physicians should be aware of the nonspecific presentation of serotonin symptoms and the treatment.

Linezolid for the treatment of drug-resistant infections

Multidrug-resistant pathogens have become increasingly common in contemporary healthcare. Specific to Gram-positive pathogens, methicillin-resistant Staphylococcus aureus (MRSA) is of particular concern, as it has been associated with increased hospital length of stay, higher healthcare expenditures and poorer outcomes. To date, linezolid is the first and only oxazolidinone approved by the US FDA for the treatment of infections caused by Gram-positive pathogens, including MRSA. This article will serve as a comprehensive review of linezolid, including an overview of the current market and its in vitro activity, with an in-depth review of its pharmacokinetic and pharmacodynamic profile. Emphasis will be placed on clinical data for the drug, both on- and off-label. The article will conclude with a brief overview of linezolid's pharmacoeconomic implications and safety profile, followed by a commentary and 5-year prospective analysis remarking on the future of the antimicrobial field as it relates to MRSA.

Pharmacokinetics and pharmacodynamics of linezolid in children with cystic fibrosis

Alternative antimicrobial regimens are needed for treatment of methicillin-resistant Staphylococcus aureus (MRSA)-associated pulmonary exacerbations in children with cystic fibrosis (CF). There are no published pharmacokinetic (PK) and pharmacodynamic (PD) data for linezolid in children with CF.

OBJECTIVES

(1) To determine the PK and PD profile of linezolid among children with CF; (2) to characterize the effect of linezolid on MRSA infection; (3) to determine the effect of age and CF transmembrane regulator (CFTR) gene mutations on drug clearance.

HYPOTHESES

Linezolid clearance is enhanced in children with CF requiring a higher dosage regimen. Age and CFTR gene mutations affect drug clearance.

METHODS

This was a retrospective cohort study; medical records of children with MRSA-associated pulmonary exacerbations treated with linezolid (10 mg/kg/dose IV every 8h) were reviewed. Linezolid peak and trough concentrations in serum were determined by high performance liquid chromatography, PK profiles determined using standard noncompartmental method, and PD indices were evaluated.

RESULTS

10 children (mean +/- SD, 10.2 +/- 5.5 years) received 14 courses of linezolid at 10 +/- 0.4 mg/kg/dose every 8h for 15.4 +/- 3.2 days. Seven had homozygous DeltaF508 CFTR mutation. Peak and trough linezolid concentrations varied widely (range, 8.4-20.5 and 0.1-11.5 mcg/mL respectively). The PK profile of children <10 years differed significantly from older patients (>or=10 years). The PK indices of children with homozygous DeltaF508 differed marginally from those with heterozygous CFTR mutations, but there were too few subjects to allow separation of age and CFTR mutations effect. No patient achieved the target PD ratio of AUC/MIC >80. MRSA persisted in sputum or throat culture after treatment with linezolid.

CONCLUSIONS

Additional PK and PD data are needed to optimize linezolid therapy in children with cystic fibrosis; it is likely that higher doses will be needed.

Serotonergic antidepressants and linezolid: a retrospective chart review and presentation of cases

OBJECTIVE

To report the results from a retrospective chart review looking at the combination of linezolid and serotonergic antidepressants and to report two cases of serotonin syndrome which were identified at our hospital.

CASE SUMMARY

During the retrospective chart review one case of serotonin syndrome was identified. A 65-year-old female was receiving escitalopram for the treatment of depression prior to admission. Linezolid therapy was initiated on admission and two days later the patient had a tonic-clonic seizure. Escitalopram was discontinued and the patient did not have any further seizure activity. In a second case, a 37-year-old male was receiving citalopram during hospitalization and was started on concomitant linezolid. The patient had myoclonus and was observed to be tremulous throughout therapy with linezolid. Ten days after discontinuation of linezolid the patient continued to have symptoms until the withdrawal of citalopram. The Naranjo probability scale scores the first case as possibly related and the second case as probably related to the combination.

DISCUSSION

It has been well documented in the literature that the combination of linezolid and serotonergic antidepressants may cause serotonin syndrome. In this retrospective chart review only one patient of 53 (1.8%) had symptoms highly suggestive of serotonin syndrome. A second patient continued to have symptoms of serotonin syndrome even after withdrawal of linezolid.

CONCLUSIONS

This retrospective review and subsequent case reports confirm the rare, but serious, potential of serotonin syndrome associated with the combination of linezolid and serotonergic antidepressants.

Linezolid-associated peripheral and optic neuropathy, lactic acidosis, and serotonin syndrome

Linezolid is an oxazolidinone antibacterial agent indicated for serious gram-positive infections. Only minor adverse effects were seen in phase III trials. However, more serious adverse effects were reported after commercial release, including cases of lactic acidosis, peripheral and optic neuropathy, and serotonin syndrome. Peripheral and optic neuropathy was usually seen after several months of linezolid therapy (median 5 mo), lactic acidosis after several weeks (median 6 wks), and serotonin syndrome after several days (median 4 days). Death occurred in two of seven reported cases of lactic acidosis, and three of 15 reported cases of serotonin syndrome. Improvement or complete recovery occurred in all cases of optic neuropathy, whereas complete recovery failed to occur in any patient with peripheral neuropathy. Linezolid should be discontinued immediately in patients experiencing these adverse effects. Patients receiving linezolid for more than 28 days should be monitored for signs of peripheral and optic neuropathy.

5-hydroxytryptamine in the cardiovascular system: focus on the serotonin transporter (SERT)

1. The function of the serotonin transporter (SERT) is to take up and release serotonin (5-hydroxytyptamine (5-HT)) from cells and this function of SERT in the central nervous system (CNS) is well-documented; SERT is the target of selective serotonin reuptake inhibitors used in the treatment of CNS disorders, such as depression. 2. The aim of the present review is to discuss our current knowledge of 5-HT and SERT in the cardiovascular (CV) system, as well as their function in physiological and pathophysiological states. 3. The SERT protein has been located in multiple CV tissues, including the heart, blood vessels, brain, platelets, adrenal gland and kidney. Modification of SERT function occurs at both transcriptional and translational levels. The functions of SERT in these tissues is largely unexplored, but includes modulation of cardiac and smooth muscle contractility, platelet aggregation, cellular mitogenesis, modulating neuronal activity and urinary excretion. 4. Recent studies have uncovered potential relationships between the expression of SERT gene promoter variants (long (l) or short (s)) with CV diseases. Specifically, the risk of myocardial infarction and pulmonary hypertension is increased with expression of the ll promoter, a variant associated with increased expression and function of SERT. The relationship between promoter variants and other CV diseases has not been investigated. 5. Newly available experimental tools, such as pharmacological compounds and genetically altered mice, should prove useful in the investigation of the function of SERT in the CV system. 6. In summary, the function of SERT in the CV system is just beginning to be revealed.

Emerging Options for Treatment of Invasive, Multidrug-ResistantStaphylococcus aureusInfections

Limited established treatment options exist for the treatment of serious, invasive infections caused by multidrug-resistant Staphylococcus aureus, most notably nosocomially acquired methicillin-resistant S. aureus (MRSA). Although vancomycin represents the gold standard for therapy of such invasive infections, reports of increasing in vitro resistance to vancomycin, combined with reports of clinical failures (with this and other antistaphylococcal agents), underscore the need for alternative therapies. Older agents with favorable in vitro activity available in both oral and intravenous dose forms include trimethoprim-sulfamethoxazole and clindamycin. Limited clinical data exist to support their routine use as initial therapy in the treatment of invasive disease. However, these and other options (e.g., tetracyclines) are being reexplored in the setting of increasing concern over MRSA acquired in the community setting. Newer treatment options for MRSA include linezolid, quinupristin-dalfopristin, daptomycin, and tigecycline. With the exception of linezolid, these newer agents require intravenous administration. Combination therapy may be considered in select invasive diseases refractory to standard monotherapies. These diseases include infections such as endocarditis, meningitis, and prosthetic device infections. Additional alternatives to vancomycin are under clinical investigation. Those in later stages of development include oritavancin, dalbavancin, telavancin, and ceftobiprole.

Risk of serotonin syndrome with concomitant administration of linezolid and serotonin agonists

Linezolid, an antimicrobial used to treat resistant gram-positive bacteria, can inhibit monoamine oxidase, an enzyme that metabolizes serotonin and other biogenic amines. Inhibition of this enzyme can predispose patients who are concomitantly taking serotonin agonists to serotonin syndrome. Because of the potential of linezolid to inhibit monoamine oxidase, premarketing studies were conducted with drugs such as selective serotonin reuptake inhibitors. No cases of serotonin syndrome were recorded. After linezolid was released to the United States market, several case reports of serotonin syndrome emerged. A literature search revealed 13 cases of serotonin syndrome occurring with the concomitant use of linezolid and drugs possessing serotonergic properties. To direct clinical management of this potential drug interaction, we reviewed reports of serotonin syndrome to determine relevant drug interactions with linezolid and serotonergic drugs and to characterize similarities and differences in the reported cases. Clinicians should obtain complete drug histories to identify patients at risk, strictly monitor drug therapy including concomitant drugs, and receive education about this potential drug interaction and the symptoms of serotonin syndrome.

Treatment of infections caused by resistant Staphylococcus aureus

We review data on the treatment of infections caused by drug-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). In this review, we cover findings reported in the English language medical literature up to February 2006. Despite the emergence of resistant and multidrug resistant S. aureus, five effective drugs for which little resistance has been observed are in clinical use: vancomycin, quinupristin-dalfopristin, linezolid, tigecycline, and daptomycin. However, vancomycin is less effective for infections with MRSA isolates that have a high minimum inhibitory concentration in the susceptible range. Linezolid looks promising in the treatment of MRSA pneumonia and skin and soft-tissue infections (SSTIs). Daptomycin displays rapid bactericidal activity in vitro, and it has been shown to be noninferior to comparator agents in the treatment of SSTIs and bacteremia. Tigecycline was also noninferior to comparator drugs in the treatment of SSTIs. Clindamycin, trimethoprim-sulfamethoxazole, doxycycline, and minocycline are oral antistaphylococcal agents that may have utility in the treatment of SSTIs and osteomyelitis, but the clinical data for their efficacy is limited. There are four drugs with broad-spectrum activity against Gram-positive organisms at an advanced stage of clinical testing: ceptobiprole and three new glycopeptides with potent bactericidal activity, oritavancin, dalbavancin, and telavancin. Thus, there are currently many effective drugs to treat resistant S. aureus infections and many promising agents in the pipeline. Nevertheless, S. aureus remains a formidable adversary against which there are frequent treatment failures. The next goals are to determine the most appropriate indications and cost-effectiveness of each of these drugs in the treatment strategy against S. aureus.

Linezolid and Serotonergic Drug Interactions: A Retrospective Survey

BACKGROUND

Linezolid is a reversible, nonselective monoamine oxidase inhibitor. There are currently 11 published case reports of serotonin syndrome being associated with linezolid and selective serotonin reuptake inhibitors (SSRIs). Controversy exists regarding whether linezolid and SSRIs can be given concomitantly. The purpose of this study was to report the incidence of serotonin syndrome in patients receiving linezolid and SSRIs.

METHODS

This study was a retrospective chart review of inpatients at the Mayo Clinic (Rochester, MN) with concomitant orders or therapy within 14 days for linezolid and an SSRI from 2000 to 2004. The Sternbach criteria and Boyer criteria for diagnosis of serotonin syndrome were used to identify clinical features of serotonin syndrome.

RESULTS

Seventy-two patients received linezolid and an SSRI or venlafaxine within 14 days of each other. Fifty-two patients (72%) received concomitant therapy with linezolid and an SSRI or venlafaxine, and 20 patients (28%) did not receive concomitant therapy but received linezolid and an SSRI within a 14-day period. Overall, only 2 patients (3%) had a high probability of serotonin syndrome. In both patients with high probability, symptoms reversed rapidly on discontinuation of serotonergic therapy. The Boyer criteria were much more specific than the Sternbach criteria for identification of serotonin syndrome.

CONCLUSIONS

On the basis of our experience, we suggest that, if the clinical situation warrants use of linezolid in a patient receiving an SSRI, linezolid may be used concomitantly with SSRIs, without a 14-day washout period and with careful monitoring for signs and symptoms of serotonin syndrome. Serotonergic agents should be promptly discontinued if serotonin syndrome is suspected.

Optimizing antimicrobial therapy for gram-positive bloodstream infections in patients on hemodialysis

Infections with gram-positive organisms are highly prevalent in hemodialysis patients and are a major cause of morbidity and mortality in this population. Antimicrobial therapy is widely used to treat these infections, and prolonged therapy with these agents is often necessary. Extensive use of antimicrobials in hemodialysis patients has resulted in a growing threat of resistance, especially among gram-positive bacteria such as Enterococcus spp and Staphylococcus aureus. Vancomycin-resistant enterococci and S. aureus isolates with reduced susceptibility to vancomycin are increasingly being reported in hemodialysis patients. Additionally, resistance of these organisms to newer agents, such as linezolid and daptomycin, has been documented. Appropriate utilization of antimicrobial therapy to treat these organisms requires an understanding of the pharmacokinetic and pharmacodynamic principles to optimize therapy and avoid adverse drug events. The pharmacokinetic and pharmacodynamic profile of antimicrobial agents can be significantly altered in patients with chronic kidney disease. This review will describe mechanisms of antimicrobial resistance among common gram-positive organisms. The pharmacokinetic and pharmacodynamic principles of cephalosporins, vancomycin, aminoglycosides, linezolid, and daptomycin and applications for use of these agents in the treatment of patients with bloodstream infections on hemodialysis are discussed.

Psychopharmacology in pediatric critical care

Psychopharmacologic treatment in pediatric critical care requires a careful child or adolescent psychiatric evaluation, including a thorough review of the history of present illness or injury, any current or pre-existing psychiatric disorder, past history, and laboratory studies. Although there is limited evidence to guide psychopharmacologic practice in this setting, psychopharmacologic treatment is increasing in critical care, with known indications for treatment, benefits, and risks; initial dosing guidelines; and best practices. Treatment is guided by the knowledge bases in pediatric physiology, psycho-pharmacology, and treatment of critically ill adults. Pharmacologic considerations include pharmacokinetic and pharmcodynamic aspects of specific drugs and drug classes, in particular elimination half-life, developmental considerations, drug interactions, and adverse effects. Evaluation and management of pain is a key initial step, as pain may mimic psychiatric symptoms and its effective treatment can ameliorate them. Patient comfort and safety are primary objectives for children who are acutely ill and who will survive and for those who will not. Judicious use of psychopharmacolgic agents in pediatric critical care using the limited but growing evidence base and a clinical best practices collaborative approach can reduce anxiety,sadness, disorientation, and agitation; improve analgesia; and save lives of children who are suicidal or delirious. In addition to pain, other disorders or indications for psychopharmacologic treatment are affective disorders;PTSD; post-suicide attempt patients; disruptive behavior disorders (especially ADHD); and adjustment, developmental, and substance use disorders. Treating children who are critically ill with psychotropic drugs is an integral component of comprehensive pediatric critical care in relieving pain and delirium; reducing inattention or agitation or aggressive behavior;relieving acute stress, anxiety, or depression; and improving sleep and nutrition. In palliative care, psychopharmacology is integrated with psychologicapproaches to enhance children's comfort at the end of life. Defining how best to prevent the adverse consequences of suffering and stress in pediatric critical care is a goal for protocols and for new psychopharmacologic research [23,153].

Serotonin toxicity associated with the use of linezolid: a review of postmarketing data

BACKGROUND

Linezolid is the first oxazolidinone antimicrobial marketed in the United States. It exhibits monoamine oxidase (MAO) type A and MAO type B inhibitory effects. The concomitant administration of nonselective MAO inhibitors or MAO-A inhibitors with drugs that increase serotonin concentrations is associated with serotonin toxicity.

METHODS

We requested from the US Food and Drug Administration all postmarketing adverse event reports regarding linezolid that included serotonin toxicity or any report describing cognitive or behavioral symptoms and autonomic and neuromuscular excitability. We assessed the case summaries obtained from the Adverse Event Reporting System database for serotonin toxicity. A case of serotonin toxicity was defined as having the following: (1) linezolid as the primary suspect drug; (2) concurrent administration of > or =1 secondary suspect drug known to increase serotonin concentrations in the central nervous system; and (3) serotonin toxicity, as defined by the modified Hunter Serotonin Toxicity Criteria or by the reporter.

RESULTS

Twenty-nine cases were classified as serotonin toxicity. Patients' ages ranged from 17-83 years, and the ratio of females to males was 1:1. The most common class of drugs received concurrently with linezolid was selective serotonin reuptake inhibitors (26 of 43 patients). Thirteen patients required an intervention to prevent permanent impairment or required hospitalization for the adverse event.

CONCLUSION

The use of linezolid with medications that increase concentrations of serotonin in the central nervous system may result in serotonin toxicity. Prescribers must weigh risks and benefits of this combination. Patients and prescribers should be cognizant of signs and symptoms of serotonin toxicity and should initiate appropriate measures if such symptoms develop.

Anticipating potential linezolid-SSRI interactions in the general hospital setting: an MAOI in disguise

Linezolid, a novel antimicrobial with activity against gram-positive bacteria including pathogens resistant to traditional antimicrobials, also inhibits monoamine oxidase. This latter property can cause potentially lethal adverse interactions with antidepressant medications. Long known to psychiatrists, monoamine oxidase inhibitors (MAOIs) and complications of their use may be unfamiliar to medical and surgical practitioners who may thus unwittingly precipitate a hypertensive crisis or serotonin syndrome. We review the pharmacology of MAOis and describe 3 clinical situations In which linezolid-selective serotonin inhibitor (SSRI) interactions, actual or potential, figured prominently.

Drug Interactions Between Linezolid and Selective Serotonin Reuptake Inhibitors: Case Report Involving Sertraline and Review of the Literature

A 47-year-old woman developed confusion, incoordination, and hypertension after she was given linezolid in addition to sertraline for 5 days. Her symptoms resolved within 4 days of discontinuing linezolid. One and a half months later, she received a second course of linezolid; sertraline was discontinued on day 1 of linezolid therapy. On day 9 of therapy, the patient developed confusion, myoclonus, and incoordination, and cardiopulmonary arrest occurred, leaving the patient in a coma. Diarrhea, hypertension, and tachycardia developed after cardiopulmonary arrest. Linezolid was discontinued on day 10, and cyproheptadine was given. Linezolid is a weak monoamine oxidase inhibitor and has been reported to interact with selective serotonin reuptake inhibitors (SSRIs). Several cases of serotonin syndrome in patients taking linezolid and SSRIs have been reported, including two reports with sertraline, one with paroxetine, four with citalopram, and two with fluoxetine. One abstract of a retrospective analysis reported that serotonin syndrome did not occur in patients who received linezolid and fluoxetine, paroxetine, or sertraline. Because of several limitations, however, no conclusions can be drawn from that retrospective analysis. A drug interaction involving escitalopram and linezolid has not been documented. Caution should be used when linezolid is used in patients receiving an SSRI. Other antibiotic options should be considered first, and linezolid should be reserved as the last resort if possible. If the infection requires linezolid, the SSRI should be discontinued, and the patient should be monitored closely for serotonin syndrome.