Benefit-risk assessment of linezolid for serious gram-positive bacterial infections.

Linezolid is an oxazolidinone, a new class of antibacterial with a unique mechanism of action, namely inhibition of the formation of a functional 70S initiation complex in the 50S bacterial ribosomal subunit. Linezolid is highly active against multidrug-resistant Gram-positive cocci, including meticillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate and vancomycin-resistant S. aureus, and vancomycin-resistant enterococci; its spectrum of activity also includes some anaerobic bacteria. Linezolid has been studied in several randomized controlled trials for the treatment of patients with community-acquired and nosocomial pneumonia, skin and soft tissue infections (SSTIs), urinary tract infections and bacteraemia. The available evidence suggests that linezolid is at least as effective as vancomycin for patients with nosocomial pneumonia, and there are some retrospective analyses supporting its superiority in comparison with vancomycin for MRSA nosocomial pneumonia, including ventilator-associated pneumonia. Linezolid is more effective than glycopeptides, macrolides and beta-lactams for SSTIs. The limited available data for the treatment of patients with bacteraemia suggest that it may be a better treatment option than vancomycin and beta-lactams for these patients, but questions have arisen regarding patients with catheter-related bacteraemias. Compared with other antibacterials, linezolid is associated with a greater frequency of adverse events, mainly nausea, vomiting, diarrhoea and headaches. Thrombocytopenia also occurs more frequently in patients taking linezolid but there is no increased frequency of anaemia. Other adverse events potentially related to linezolid therapy include fungal infections (moniliasis), hypertension and serotonin-like syndrome, tongue discolouration and taste alterations, dizziness, insomnia, rash and Clostridium difficile-related diarrhoea. The majority of adverse events develop after prolonged administration (i.e. >2 weeks) and subside shortly after discontinuation of linezolid. Peripheral or optic neuropathy, another possible adverse effect, is associated with an even longer duration of treatment (3-6 months). In conclusion, linezolid is an important treatment option for the treatment of patients with multidrug-resistant, Gram-positive bacterial infections. However, in order to reduce the possibility of development of resistance and preserve its activity, the use of linezolid should be restricted to treatment of patients with infections associated with high morbidity and mortality, particularly those caused by multidrug-resistant bacteria.