Linezolid-associated toxic optic neuropathy

Linezolid-induced lactic acidosis

Linezolid is a commonly prescribed antibiotic in clinical practice. Although thrombocytopenia and peripheral neuropathy are frequently encountered following prolonged administration of linezolid, lactic acidosis is a rare adverse drug reaction. We present the case of a patient on linezolid for disseminated multidrug-resistant tuberculosis who presented with vomiting, dyspnoea, hypotension and high anion gap metabolic acidosis. The initial presentation mimicked sepsis syndrome. Ketoacidosis and renal dysfunction were ruled out. There was no history of ingestion of toxins/toxic alcohols. Sepsis was unlikely because extensive radiological and microbiological testing could not identify an infection. Given the possibility of linezolid-induced lactic acidosis (LILA), linezolid was discontinued on admission. The patient's lactic acidosis resolved, and his overall condition improved. A retrospective diagnosis of LILA was thus established. LILA should be considered when patients on linezolid present with lactic acidosis and other causes for the lactic acidosis have been ruled out.

Predicting 60-4 visual field tests using 3D facial reconstruction

BACKGROUND

Despite, the potential clinical utility of 60-4 visual fields, they are not frequently used in clinical practice partly, due to the purported impact of facial contour on field defects. The purpose of this study was to design and test an artificial intelligence-driven platform to predict facial structure-dependent visual field defects on 60-4 visual field tests.

METHODS

Subjects with no ocular pathology were included. Participants were subject to optical coherence tomography, 60-4 Swedish interactive thresholding algorithm visual field tests and photography. The predicted visual field was compared with observed 60-4 visual field results in subjects. Average and point-specific sensitivity, specificity, precision, negative predictive value, accuracy, and F1-scores were primary outcome measures.

RESULTS

30 healthy were enrolled. Three-dimensional facial reconstruction using a convolution neural network (CNN) was able to predict facial contour-dependent 60-4 visual field defects in 30 subjects without ocular pathology. Overall model accuracy was 97%±3% and 96%±3% and the F1-score, dependent on precision and sensitivity, was 58%±19% and 55%±15% for the right eye and left eye, respectively. Spatial-dependent model performance was observed with increased sensitivity and precision within the far inferior nasal field reflected by an average F1-score of 76%±20% and 70%±29% for the right eye and left eye, respectively.

CONCLUSIONS

This pilot study reports the development of a CNN-enhanced platform capable of predicting 60-4 visual field defects in healthy controls based on facial contour. Further study with this platform may enhance understanding of the influence of facial contour on 60-4 visual field testing.

Linezolid toxic optic neuropathy: A case report and review of visual prognosis

Purpose

To describe a case of linezolid toxic optic neuropathy in a 71-year-old female and review the relevant literature.

Observations

An adult female with progressive, symmetric vision loss was hypothesized to have linezolid toxic optic neuropathy. Following cessation of linezolid, the patient experienced improvement in visual function over two months.

Conclusions and importance

Patients diagnosed with linezolid toxic optic neuropathy can expect some return of visual function after cessation. The degree of return does not correlate to the cumulative dose of the drug. The goal of this study was to summarize and add to the current body of literature on the topic.

Linezolid optic neuropathy

PURPOSE OF REVIEW

In this article, we reviewed 67 reported cases of linezolid optic neuropathy and describe the common characteristics and expectations for recovery with an emphasis on recent findings in the literature.

RECENT FINDINGS

Linezolid classically causes a reversible, duration-dependent optic neuropathy. However, in our review, we found only 66.7% of patients recovered complete visual function. Vision loss most commonly affected visual acuity followed by visual field and color vision. We also found patients taking higher doses of linezolid experienced full recovery less often, suggesting a dose-dependent component of linezolid optic neuropathy. Linezolid use has increased in frequency and duration, especially in the treatment of drug-resistant tuberculosis, and data indicate that these patients experience lower rates of complete vision recovery compared with patients taking linezolid for other indications.

SUMMARY

Linezolid is an effective medication for treating drug-resistant infections; however, it may result in optic neuropathy. It is reasonable for patients on linezolid to undergo screening examinations, especially those on higher doses or for prolonged duration of therapy.

Safety Profile of Linezolid in Older Adults With Renal Impairment: A Population-Based Retrospective Cohort Study

Background

The objective of this study was to characterize the safety profile of linezolid in patients with renal impairment compared with patients without renal impairment.

Methods

A population-based retrospective cohort study using linked administrative databases included patients aged 66 years or older in Ontario, Canadawho were prescribed linezolid from 2014 to 2021. Renal impairment was defined using baseline estimated glomerular filtration rate <30 mL/min/1.73 m² or receipt of dialysis. The primary outcomes were change in platelet count and severe thrombocytopenia (platelet count <50 × 10⁹/L) within 90 days. Secondary outcomes included bleeding, neutropenia, peripheral neuropathy, optic neuropathy, acidosis, serotonin syndrome, and mortality. Inverse probability of treatment weighting on propensity score was used to balance comparison groups on baseline health.

Results

Of 625 patients, 98 (15.7%) patients had renal impairment. The mean (SD) platelet change was -88.3 (108.4) 10⁹/L in the renal impairment group and -76.5 (109.8) 10⁹/L in the no renal impairment group, with an adjusted mean difference of -29.4 (95% CI, -53.4 to -5.3; P = .0165). Severe thrombocytopenia occurred in 9.2% for the renal impairment group and 5.9% for the no renal impairment group, with an adjusted risk difference of 2.7% (95% CI, -3.1% to 8.6%; P = .3655). There were no significant differences in secondary outcomes between the 2 groups.

Conclusions

Patients with renal impairment on linezolid therapy had a larger decrease in platelet count, but their risks for severe thrombocytopenia and bleeding were not significantly different than patients without renal impairment. Linezolid is likely safe in renal impairment without dose adjustment or drug level monitoring.

MDR Tuberculosis Treatment

Multidrug-resistant (MDR) tuberculosis (TB), resistant to isoniazid and rifampicin, continues to be one of the most important threats to controlling the TB epidemic. Over the last few years, there have been promising pharmacological advances in the paradigm of MDR TB treatment: new and repurposed drugs have shown excellent bactericidal and sterilizing activity against Mycobacterium tuberculosis and several all-oral short regimens to treat MDR TB have shown promising results. The purpose of this comprehensive review is to summarize the most important drugs currently used to treat MDR TB, the recommended regimens to treat MDR TB, and we also summarize new insights into the treatment of patients with MDR TB.

Intravitreal linezolid in the management of vancomycin-resistant enterococcal endophthalmitis

Purpose

Linezolid is a synthetic antibiotic, the first of the oxazolidinone class, used for the treatment of infections caused by multi-resistant bacteria including Streptococcus, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). We report on a case of endophthalmitis caused by vancomycin-resistant Enterococcus feacium treated with intravitreal linezolid. It has proved efficacious in animal models but its safety in humans is not fully known.

Observations

An 84-year-old man who had phacoemulsification surgery and anterior chamber intraocular lens due to posterior capsule rent. Visual acuity (VA) following surgery was 6/24 uncorrected. The following week he developed signs of endophthalmitis, characterized by corneal infiltration and keratic precipitates, with anterior chamber and vitreous haze. Cultures yielded no growth, while repeated treatments with intravitreal vancomycin, ceftazidime, and amphotericin B did not control the infection. Vitrectomy was performed twice during the patient's course, with intravitreal amikacin injection after the second vitrectomy, but poor control of the endophthalmitis persisted. After several weeks of limited response to treatments, the diagnosis was finally made using Giemsa stain of direct smear which showed characteristic morphology of Enterococcus faecium. Linezolid, one of the oxazo-lidinones, was initially given in oral form 600 mg BID for three weeks, but did not prove efficacious. Subsequently, intravitreal linezolid 200 mcg in 0.1ml was injected, which cleared the vitreous and cornea infection within a week. However, there was a residual exudative detachment of the retina in the posterior pole, leaving the patient with a final vision of hand movement.

Conclusion and importance

Vancomycin-resistant enterococcus is a rare cause of endophthalmitis. Intravitreal linezolid is an effective treatment, but the subsequent exudative retinal detachment may have been related to this novel therapy.

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.

Is Severe and Long-lasting Linezolid-induced Optic Neuropathy Reversible?

Linezolid is a useful drug for treating drug-resistant tuberculosis. However, the associated toxicities, especially optic neuritis, are a major obstacle for its long-term use. We recently experienced a case of severe optic and peripheral neuropathy during the treatment of multidrug-resistant tuberculosis. The treatment continued for 12 months despite severe optic and peripheral neuropathy. At eight months after the discontinuation of the drug, the optic neuropathy recovered, but the peripheral neuropathy did not. Considering the grave prognosis of drug-resistant tuberculosis, the continuation of linezolid despite neurotoxicity under close observation may be a suitable option.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Linezolid-associated optic neuropathy in a pediatric patient with Mycobacterium nonchromogenicum: A case report

BACKGROUND

Toxic optic neuropathies are alterations of the optic nerve and can be caused by environmental, pharmacological, or nutritional agents.

CASE

It is about a 7-year-old male patient, a native of the State of Mexico, Mexico who was diagnosed with cervical mycobacterial lymphadenitis that required management with linezolid.

OBSERVATIONS

After 7 months of treatment, visual acuity of the left eye decreased and was accompanied by headache. Neuroinfection and other central nervous system affections were discarded. An adverse effect related to treatment with linezolid was suspected, and linezolid was suspended. The symptoms subsided after discontinuation; however, the patient continued to show decreased visual acuity of the left eye, assessed by his ability to count 2 fingers. The right eye remained unaffected.

CONCLUSIONS

Neurotoxicity can be decreased by reducing the total dose of linezolid or by administrating it in an intermittent form. To avoid progression and loss of vision, we suggest frequent periodic ophthalmological evaluation in patients treated with linezolid.

A Review of Mitochondrial Optic Neuropathies: From Inherited to Acquired Forms

In recent years, the term mitochondrial optic neuropathy (MON) has increasingly been used within the literature to describe a group of optic neuropathies that exhibit mitochondrial dysfunction in retinal ganglion cells (RGCs). Interestingly, MONs include genetic aetiologies, such as Leber hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA), as well as acquired aetiologies resulting from drugs, nutritional deficiencies, and mixed aetiologies. Regardless of an inherited or acquired cause, patients exhibit the same clinical manifestations with selective loss of the RGCs due to mitochondrial dysfunction. Various novel therapies are being explored to reverse or limit damage to the RGCs. Here we review the pathophysiology, clinical manifestations, differential diagnosis, current treatment, and promising therapeutic targets of MON.

Vision loss in tuberculous meningitis

Vision loss is a disabling complication of tuberculous meningitis. Approximately, 15% of survivors are either completely or partially blind. All structures of the visual pathway may be affected in tuberculous meningitis. Optic nerve and optic chiasma are most frequently and dominantly affected. Thick-gelatinous exudates lying over the base of brain, are the pathological hallmark of tuberculous meningitis and are responsible for almost all of its major complications, including vision loss. Strangulation of optic nerves and optic chiasma by the exudates, compression over optic chiasma by the dilated third ventricle, raised intracranial pressure, endarteritis, shunt failure, bacterial invasion of optic nerves and drug-induced optic nerve damage are important reasons that are considered responsible for vision loss. Prompt antituberculosis treatment is the best management option available. Immunomodulatory drugs and cerebrospinal fluid diversion procedures are of limited help. Early recognition and treatment of tuberculous meningitis is the only way forward to tackle this problem.

Linezolid-Associated Optic Neuropathy in Drug-Resistant Tuberculosis Patients in Mumbai, India

Background

Patients on linezolid-containing drug-resistant TB (DR-TB) regimen often develop adverse-events, particularly peripheral and optic neuropathy. Programmatic data and experiences of linezolid-associated optic neuropathy from high DR-TB burden settings are lacking. The study aimed to determine the frequency of and risk-factors associated with linezolid-associated optic neuropathy and document the experiences related to treatment/care of DR-TB patients on linezolid-containing regimens.

Methods

This was a retrospective cohort study using routine clinical and laboratory data in Médecins Sans Frontières (MSF) HIV/DR-TB clinic in collaboration with Lilavati Hospital & Research Center, Mumbai, India. All DR-TB patients on linezolid-containing treatment regimens were included in the study and underwent routine evaluations for systemic and/or ocular complaints. Ophthalmological evaluation by a consultant ophthalmologist included visual-acuity screening, slit-lamp examination and dilated fundus examination.

Results

During January 2013-April 2016, 86 of 136 patients (with/without HIV co-infection) initiated linezolid-containing DR-TB treatment. The median age of these 86 patients was 25 (20–35) years and 47% were males. 20 percent of them had HIV co-infection. Of 86, 24 (27.9%) had at least one episode of ocular complaints (the majority blurred-vision) and among them, five (5.8%) had optic neuropathy. Patients received appropriate treatment and improvements were observed. None of the demographic/clinical factors were associated with optic neuropathy in Poissons or multivariate binary logistic-regression models.

Discussion

This is the first report focusing on optic neuropathy in a cohort of complex DR-TB patients, including patients co-infected with HIV, receiving linezolid-containing regimens. In our study, one out of four patients on linezolid had at least one episode of ocular complaints; therefore, systematic monitoring of patients by primary physicians/nurses, and access to specialized diagnostic-services by specialists are needed. As linezolid will be increasingly added to treatment regimens of DR-TB patients, programmes should allocate adequate resources for early diagnosis, prevention and management of this disabling adverse event.

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.

Linezolid-induced optic neuropathy with a rare pathological change in the inner retina

We report a case of linezolid-induced optic neuropathy with transient microcystic spaces in the inner retina. We observed the retina using Fourier-domain optical coherence tomography (FD-OCT) in a patient with linezolid-induced optic neuropathy. A 49-year-old woman presented to our department with a 1-week history of bilateral photophobia. At the first visit, her best-corrected visual acuity (VA) was 0.6 in the right eye and 0.5 in the left eye. She had moderate optic disk edema and central scotomas bilaterally. FD-OCT showed bilateral microcystic spaces in the retina. Microcystic spaces were seen in the retinal nerve fiber layer (RNFL) and at the border of the RNFL and the retinal ganglion cell layer. Magnetic resonance imaging and laboratory tests showed no positive findings except for an elevated lactic acid level. One week after the first visit, the VA levels decreased to 0.06 and 0.07 in the right and left eyes, respectively. Because the patient had a 7-month history of linezolid treatment for persistent pyogenic arthritis, we suspected linezolid-induced optic neuropathy and immediately terminated treatment with this drug. The optic disk edema and the microcystic spaces in the retina resolved, and the VA improved to 1.2 at 6 weeks after linezolid withdrawal. Microcystic spaces, which resolved with linezolid withdrawal, were observed in linezolid-induced optic neuropathy. The microcystic spaces in the inner retina can be the first retinal sign of some optic neuropathies.

Toxicity to sensory neurons and Schwann cells in experimental linezolid-induced peripheral neuropathy

OBJECTIVES

Peripheral neuropathy is a common side effect of prolonged treatment with linezolid. This study aimed to explore injurious effects of linezolid on cells of the peripheral nervous system and to establish in vivo and in vitro models of linezolid-induced peripheral neuropathy.

METHODS

C57BL/6 mice were treated with linezolid or vehicle over a total period of 4 weeks. Animals were monitored by weight, nerve conduction studies and behavioural tests. Neuropathic changes were assessed by morphometry on sciatic nerves and epidermal nerve fibre density in skin sections. Rodent sensory neuron and Schwann cell cultures were exposed to linezolid in vitro and assessed for mitochondrial dysfunction.

RESULTS

Prolonged treatment with linezolid induced a mild, predominantly small sensory fibre neuropathy in vivo. Exposure of Schwann cells and sensory neurons to linezolid in vitro caused mitochondrial dysfunction primarily in neurons (and less prominently in Schwann cells). Sensory axonopathy could be partially prevented by co-administration of the Na(+)/Ca(2+) exchanger blocker KB-R7943.

CONCLUSIONS

Clinical and pathological features of linezolid-induced peripheral neuropathy can be replicated in in vivo and in vitro models. Mitochondrial dysfunction may contribute to the axonal damage to sensory neurons that occurs after linezolid exposure.

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.

Systematic review and meta-analysis of the efficacy and safety of therapy with linezolid containing regimens in the treatment of multidrug-resistant and extensively drug-resistant tuberculosis

BACKGROUND

Linezolid containing regimens have been proposed as potentially valuable alternatives for the treatment of patients with multidrug-resistant tuberculosis (MDR-TB) or extensively drug-resistant TB (XDR-TB).

METHODS

A systematic review and meta-analysis was conducted to assess the efficacy, safety and tolerability of linezolid for drug-resistant TB (DR-TB) treatment. We searched the Cochrane Controlled Trial Registry, PubMed, Embase, Science Citation Index Expanded (SCI) and China National Knowledge Infrastructure (CNKI), database up to May 2014 to identify studies providing data of the use of linezolid for the treatment of DR-TB.

RESULTS

The search yielded 15 studies (367 patients) including one randomized controlled trial (RCT), covering 239 patients who could be evaluated for effectiveness; 83% [95% confidence interval (CI), 75-90%; I(2)=62.8%] had a favorable outcome, defined as either cure or treatment completion. The pooled rate of culture conversion was 89% (95% CI, 83-95%; I(2)=49.6%). Between the group receiving daily linezolid doses of ≤600 or >600 mg, the mortality was considerably lower in patients treated with less than 600 mg/day (P value <0.001). Of 367 patients for whom data on safety was available, peripheral neuropathy (31%, 95% CI, 19-42%; I(2)=81.7%) and anemia (25%, 95% CI, 15-34%; I(2)=76.6%) were the main adverse effects. Patients receiving less than 600 mg/day were more likely to experience nervous system adverse events (P value <0.01).

CONCLUSIONS

The available evidence suggests that linezolid could be considered as a promising option as treatment of MDR/XDR TB. Randomized trials are warranted to define the dose and frequency of administration.

Antibiotic-induced neurotoxicity

Antibiotic neurotoxicity is rare but can cause significant morbidity when it occurs. The risk of antibiotic neurotoxicity appears to be highest in patients who are older, have impaired renal function, or have preexisting neurologic conditions. This review describes the clinical features of the most common antibiotic toxicities affecting the nervous system: seizures, encephalopathy, optic neuropathy, peripheral neuropathy, and exacerbation of myasthenia gravis.

Ceftaroline fosamil for the treatment of acute bacterial skin and skin structure infections

Skin infections have traditionally been classified by the US FDA as uncomplicated and complicated. In August 2010, the FDA released a new guidance document for the development of drugs to treat acute bacterial skin and skin structure infections (ABSSSI) and this was updated in 2013. Several new issues were addressed and henceforth skin infections in clinical trials were termed ABSSSI. In the USA, the annual prevalence of methicillin-resistant Staphylococcus aureus-related skin infections have continuously increased from 32.7% in 1998 to 53.8% in 2007. Ceftaroline fosamil is the only cephalosporin approved in the USA for monotherapy treatment of ABSSSI including infections caused by methicillin-resistant S. aureus. The efficacy of ceftaroline fosamil was shown in the CANVAS clinical trials. The CANVAS Day-3 analyses met an earlier, primary efficacy time point requested by the FDA. Ceftaroline has minimal drug-drug interactions, is well tolerated and possesses the safety profile associated with the cephalosporin class.

Toxic optic neuropathies

PURPOSE OF REVIEW

Many causes of toxic optic neuropathy have been described to date and novel causes of toxicity are continuously being added to the current literature. The pathophysiological basis for the toxicity or a direct causal relationship is yet to be determined for many of these agents. This review highlights the reports made over the last year about the commonly reported agents, with emphasis on the mechanisms of toxicity.

RECENT FINDINGS

Mitochondria of retinal ganglion cells and papillomacular bundle in particular could be the common target of many causes of toxic optic neuropathy, if not all. Agents or their metabolites responsible for the toxicity seem to interfere with the oxidative phosphorylation in mitochondria, causing a buildup of reactive oxidation species, energy depletion, oxidative stress, and activation of apoptosis.

SUMMARY

Further data are still necessary to understand how some of the usual suspects cause damage to the optic nerve or whether they indeed cause damage or not. A basic algorithm, as proposed, could be a useful addition to discriminate the novel causes of toxic optic neuropathy.

VIDEO ABSTRACT

See the Supplemental Digital Content 1 (http://links.lww.com/COOP/A11).

Changes in chest CT findings of pulmonary tuberculosis after linezolid treatment

The purpose of the present study was to evaluate the changes in successive chest CT examinations in patients with pulmonary tuberculosis who achieved culture conversion with linezolid treatment. We reviewed the follow-up CT scans of 14 patients with pulmonary tuberculosis who had sputum-culture conversion after linezolid treatment. This study evaluated cavity, centrilobular nodules, consolidation, bronchial wall thickening, calcified nodule or consolidation, bronchiectasis, irregular lines, and lung destruction. The presence of pleural thickening, pleural effusion and lymphadenopathy was recorded. Follow-up CT scans showed a partial decrease in the extent of centrilobular nodules in all cases. Consolidation was partially cleared in 8 patients and newly developed consolidation was observed in 2 patients. All of the cavities showed a decrease in size and thickness. But the cavities persisted after linezolid treatment in 8 of 9 patients. Bronchial wall thickening was completely or partially cleared in 6 patients and 5 patients, respectively. Newly developed irregular lines, lung destruction and pleural thickening were observed in 1, 1, and 3 patients, respectively. Successive chest CT examinations in patients with linezolid treatment may help in the early assessment of linezolid treatment efficacy because of its rapid availability. Early assessment of linezolid treatment efficacy will help to set up a treatment plan, such as duration of treatment or linezolid dosage. However, they may not be useful for deciding pulmonary tuberculosis activity following linezolid treatment.

Ocular toxicity from systemically administered xenobiotics

INTRODUCTION

The eye is considered as the most privileged organ because of the blood-ocular barrier that acts as a barrier to systemically administered xenobiotics. However, there has been a significant increase in the number of reports on systemic drug-induced ocular complications. If such complications are left untreated, then it may cause permanent damage to vision. Hence, knowledge of most recent updates on ever-increasing reports of such toxicities has become imperative to develop better therapy while minimizing toxicities.

AREAS COVERED

The article is mainly divided into anterior and posterior segment manifestations caused by systemically administered drugs. The anterior segment is further elaborated on corneal complications where as the posterior segment is focused on optic nerve, retinal and vitreous complications. Furthermore, this article includes recent updates on acute and chronic ocular predicaments, in addition to discussing various associated symptoms caused by drugs.

EXPERT OPINION

Direct correlation of ocular toxicities due to systemic drug therapy is evident from current literature. Therefore, it is necessary to have detailed documentation of these complications to improve understanding and predict toxicities. We made an attempt to ensure that the reader is aware of the characteristic ocular complications, the potential for irreversible drug toxicity and indications for cessation.

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.

Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies

Leber hereditary optic neuropathy (LHON) and autosomal-dominant optic atrophy (DOA) are the two most common inherited optic neuropathies in the general population. Both disorders share striking pathological similarities, marked by the selective loss of retinal ganglion cells (RGCs) and the early involvement of the papillomacular bundle. Three mitochondrial DNA (mtDNA) point mutations; m.3460G>A, m.11778G>A, and m.14484T>C account for over 90% of LHON cases, and in DOA, the majority of affected families harbour mutations in the OPA1 gene, which codes for a mitochondrial inner membrane protein. Optic nerve degeneration in LHON and DOA is therefore due to disturbed mitochondrial function and a predominantly complex I respiratory chain defect has been identified using both in vitro and in vivo biochemical assays. However, the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa. The downstream consequences of these mitochondrial disturbances are likely to be influenced by the local cellular milieu. The vulnerability of RGCs in LHON and DOA could derive not only from tissue-specific, genetically-determined biological factors, but also from an increased susceptibility to exogenous influences such as light exposure, smoking, and pharmacological agents with putative mitochondrial toxic effects. Our concept of inherited mitochondrial optic neuropathies has evolved over the past decade, with the observation that patients with LHON and DOA can manifest a much broader phenotypic spectrum than pure optic nerve involvement. Interestingly, these phenotypes are sometimes clinically indistinguishable from other neurodegenerative disorders such as Charcot-Marie-Tooth disease, hereditary spastic paraplegia, and multiple sclerosis, where mitochondrial dysfunction is also thought to be an important pathophysiological player. A number of vertebrate and invertebrate disease models has recently been established to circumvent the lack of human tissues, and these have already provided considerable insight by allowing direct RGC experimentation. The ultimate goal is to translate these research advances into clinical practice and new treatment strategies are currently being investigated to improve the visual prognosis for patients with mitochondrial optic neuropathies.

In vitro electrophysiological investigations of the acute effects of linezolid and novel oxazolidinones on central nervous system neurons

Oxazolidinones are a novel class of antibacterial agents with demonstrated activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and enterococci. Prolonged clinical use of linezolid, the prototypical oxazolidinone, results in peripheral, central and optic neuropathies. The cellular mechanism by which it may alter neuronal function to produce these effects is not known. This study examined the in vitro effects of clinically relevant concentrations of linezolid and four selected potent antibacterial oxazolidinones on neuronal responses to determine if they are neuroactive and their possible neurotoxic mechanism(s). Using in vitro slice preparations of the rat nucleus accumbens (NAc) and hippocampus, we examined the effects of linezolid and the potent antibacterial triazolyl oxazolidinones, PH027, PH036, PH084 and PH108 on synaptic transmission and neuronal excitability recorded in voltage or current clamp mode. PH027 and PH084 generally depressed all excitatory and inhibitory postsynaptic currents. Linezolid, at the highest concentration tested, depressed NMDA receptor-mediated currents while PH036 and PH108 had no significant effect on any of these responses. The synaptic depression by PH084 was without effect on the resting membrane conductance at resting or relatively hyperpolarized voltage and could be blocked by GABA(B), dopamine D1-like and α-adrenergic receptor antagonists but not by an adenosine A1 receptor antagonist. Finally, PH084 decreased action potential firing frequency of NAc and hippocampal cells elicited at depolarized potentials. Our data indicate that, while oxazolidinones containing both the morpholine and triazole functional groups, as in PH027 and PH084, have neuroactivity, those containing morpholine and acetamide (linezolid) or piperazine and triazolyl (PH036 and PH108) functional groups have minimal acute neuroactivity and therefore may be safer antibacterial agents.

Peripheral Visual Field Thresholds using Humphrey Field Analyzer Program 60–4 in Normal Eyes

Purpose

Various methods have been used for testing peripheral visual field disturbances such as defects caused by drug toxicity. Static threshold perimetry with Humphrey Field Analyzer (HFA) is widely available. The aim of this study was to better define the normal thresholds for peripheral visual field (PVF) sensitivity and to refine analysis strategies.

Methods

Automated PVF testing was performed with HFA 60–4 program in 33 normal subjects. Test locations were organized into inner, middle, and outer eccentricity rings and divided into 4 zones: nasal, temporal, superior, and inferior. The threshold visual sensitivity (TVS) in decibels was established for each point.

Results

The majority of points with the lowest TVS and highest between-subject variability were located within the nasal area of the outer ring. Points with the highest TVS and least variability were detected in the inner ring and in the temporal area of the middle and outer rings. Mean zone TVS decreased and variability increased with increasing eccentricity.

Conclusions

The areas that demonstrate the highest between-subject consistency and thus might best reveal peripheral visual abnormalities with HFA 60–4 are the inner ring, inferior and temporal zone of the middle ring, and temporal zone of the outer ring. These observations may be useful for developing strategies to detect peripheral field loss at an early stage when central vision is not yet affected.

Abnormalities of the optic disc

The optic disc represents the anterior end of the optic nerve, the most forward extension of the central nervous system (CNS). The optic disc gives a rare glimpse into the CNS. Hence, diseases of the CNS are often manifested on fundus examination. Abnormalities of the optic disc may reflect eye disease (such as glaucoma), problems in development (as in various syndromes), or CNS disease (such as increased intracranial pressure). Each optic nerve is composed of about 1.2 million axons deriving from the retinal ganglion cells of one eye. Optic atrophy is a morphological sequela reflecting the loss of many or all of these axons. Myriad diseases such as hereditary, metabolic, tumor, and increased intracranial pressure can lead to optic atrophy. Some diseases, such as optic disc drusen, intracranial masses, orbital tumors, ischemic optic neuropathies, inflammations, and infiltrations, can produce optic disc edema before leading to optic atrophy. A number of new imaging modalities, such as optical coherence tomography (OCT), quantitate the thickness of the peripapillary retinal nerve fiber layer as an indirect measure of axonal loss or swelling. OCT can therefore be used to quantitate pathology or the response to therapy in various generalized CNS conditions, such as multiple sclerosis.

Lesions of the optic nerve

As experts on the central nervous system, neurologists are expected to be familiar with the many conditions that can result in visual loss arising from lesions of the optic nerve. The optic nerves are unique central nervous system structures in terms of surrounding anatomy, size, location, and blood supply; therefore, they are uniquely vulnerable to every pathological process that can affect the central and peripheral nervous systems, including inflammation, ischemia, compression, infiltration, toxic or hereditary metabolic dysfunction, trauma, and mechanical damage. This chapter highlights the importance of being able to identify the historical and clinical features that will enable neurologists to narrow down the broad differential diagnosis of optic nerve lesions. Distinguishing an optic neuropathy on the basis of history and clinical examination alone, however, can be difficult, especially when bilateral optic neuropathies are present. Specific ancillary tests, especially new imaging modalities, help further localization and differential diagnosis.

Comparison of the pharmacokinetics of two dosage regimens of linezolid in multidrug-resistant and extensively drug-resistant tuberculosis patients

BACKGROUND AND OBJECTIVES

For the treatment of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB), potent new drugs are urgently needed. Linezolid is a promising drug, but its use is limited by adverse effects with prolonged administration of 600 mg twice daily. In order to reduce its adverse effects and maintain efficacy, we investigated whether linezolid in a reduced dosage resulted in drug serum concentrations exceeding a ratio of the in vitro minimum inhibitory concentration (MIC) to the area under the serum concentration-time curve (AUC) over 24 hours (AUC(24)) [AUC(24)/MIC] of >100.

PATIENTS AND METHODS

This open-label, prospective pharmacokinetic study evaluated two doses (300 and 600 mg) of linezolid in MDR-TB patients, who received linezolid as part of their treatment. They received linezolid 300 mg twice daily for 3 days, followed by 600 mg twice daily. Blood samples taken at predefined intervals for measuring serum linezolid concentrations were processed by a validated liquid chromatography-tandem mass spectrometry procedure. The AUC(24)/MIC ratio was used as a predictive model of efficacy. Adverse effects of linezolid, including peripheral neuropathy, were evaluated by clinical and laboratory assessments.

RESULTS

Eight patients were included in this study. The median duration of linezolid treatment was 56 days (interquartile range [IQR 44-82] days), with a median cumulative dose of 51,000 mg (IQR 33,850-60,450 mg). The median linezolid AUC over 12 hours (AUC(12)) values were 57.6 mg x h/L (IQR 38.5-64.2 mg x h/L) with the 300 mg dose and 145.8 mg x h/L (IQR 101.2-160.9 mg x h/L) with the 600 mg dose. The AUC(24)/MIC ratios were 452 (IQR 343-513) with the 300 mg dose and 1151 (IQR 656-1500) with the 600 mg dose. Linezolid was well tolerated.

CONCLUSION

Seemingly effective serum concentrations were reached after 3 days of administration of linezolid 300 mg twice daily, i.e. the AUC(24)/MIC ratio was at least 100 in 7 of 8 patients. Larger numbers of patients should be studied to confirm the efficacy of the linezolid 300 mg twice-daily dosage in MDR-TB or XDR-TB treatment.

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.

Linezolid-associated optic neuropathy in a patient with ocular sarcoidosis

BACKGROUND

We describe a case of bilateral linezolid-associated optic neuropathy in a patient with ocular sarcoidosis.

CASE

A 70-year-old woman with sarcoidosis noted foggy vision in both eyes. Best-corrected visual acuity was 0.5 in the right eye and 0.9 in the left. No abnormality other than slight optic disc hyperemia was visible in either eye. A central scotoma in both eyes and enlargement of the blind spot in the right eye were detected by Goldmann perimetry examination, and magnetic resonance imaging demonstrated an edematous optic nerve in the right eye. Therefore, retrobulbar optic neuritis resulting from sarcoidosis was initially suspected. Sub-Tenon's capsule injection of triamcinolone acetonide along with steroid pulse therapy was given; however, best-corrected visual acuity worsened to 0.06 in the right eye and 0.08 in the left. Pulse therapy was discontinued on day 1, and the possibility of linezolid-associated optic neuropathy was speculated because linezolid had been given for methicillin-resistant Staphylococcus aureus osteomyelitis 2 years before by an orthopedist. After discontinuation of linezolid, best-corrected visual acuity improved to 0.8 in the right eye and 0.9 in the left, and the optic disc hyperemia in both eyes disappeared.

CONCLUSION

Our findings demonstrate that it is important for ophthalmologists as well as physicians and orthopedists to consider the possibility of optic neuropathy caused by long-term use of linezolid.

5-Hydroxymethyl-oxazolidin-2-one antibacterials. Actelion Pharmaceuticals: WO2008062379

The application, WO2008062379, claims chimeric compounds comprising chemically linked 5-hydroxymethyl-oxazolidinone and tetracyclic-quinolone moieties. The claimed compounds are potent expanded-range antibacterial agents against selected gram-positive and gram-negative bacteria, which may exhibit dual mode of action as inhibitors of topoisomarases IV and protein synthesis. The structures of the compounds suggest that the linkers are chemically and biochemically stable. This application represents part of recently initiated research efforts at Actelion.

Update on medication-induced peripheral neuropathy

Despite improvements in the identification of causes of peripheral neuropathy, idiopathic polyneuropathy remains common. Medication and toxic neuropathy account for a small but important percentage of potentially preventable or reversible causes of neuropathy. New drugs that can induce neuropathy have been approved over the past several years, including the anticancer agents bortezomib, ixabepilone, and oxaliplatin. We review the neurotoxic effects of tumor necrosis factor-alpha blockers infliximab and etanercept, the inflammatory arthritis agent leflunomide, and the antibiotic linezolid. The controversy of statin-induced neuropathy continues to unfold; the large Fremantle Diabetes Study has suggested that statins may have neuroprotective effects. Dichloroacetate is a promising agent for lactic acidosis-associated disorders, but toxic neuropathy is a treatment-limiting factor. We also describe a progressive inflammatory neuropathy in swine slaughterhouse workers that appears to be a toxin-induced immune response.