Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Zyvox (Pharmacia)
600 mg film-coated tablets
granules for oral suspension (20 mg/mL)
infusion bags containing 600 mg/300 mL
Approved indication: specified infections
Australian Medicines Handbook Section 5.1

The oxazolidinones are a new class of antibiotic. They are likely to have a role in the treatment of infections caused by resistant organisms.

Linezolid is the first drug of the class to be approved in Australia. Its inhibition of bacterial protein synthesis makes it bacterio static against staphylococci and enterococci, and bactericidal against most streptococci. Linezolid can be used to treat methicillin-resistant staphylococci and vancomycin-resistant enterococci. It is not active against Haemophilus influenzae, Pseudomonas aeruginoia, Neisseria or Enterobacteriaceae. Legionella and Moraxellacatarrhalis are only intermediately susceptible to linezolid.

When taken by mouth, linezolid is almost completely absorbed. It has a half-life of 5-7 hours and is mainly eliminated by metabolism. As linezolid weakly inhibits monoamine oxidase there is a potential for interactions with tyramine and sympathomimetic drugs such as pseudoephedrine.

Adverse effects are common; 70% of the patients in one study had an adverse event.1 The most frequent problems are headache, nausea, diarrhoea and candidiasis. Liver function is commonly disturbed and some patients develop myelosuppression. The haemoglobin and platelet count should be checked in any patient who takes linezolid for more than two weeks. Patients are also at risk of pseudomembranous colitis.

Some of the trials investigating the efficacy of linezolid have not been published. One published study was a double-blind comparison with vancomycin for the treatment of 396 patients with nosocomial pneumonia. Approximately 18% of the inpatients given linezolid died compared with 25% of the vancomycin group. None of the deaths in the linezolid group were due to a lack of response. The cure rate was 53% for linezolid and 52% for vancomycin.1

Although linezolid has been studied in soft tissue infections and community-acquired pneumonia, as well as in nosocomial pneumonia, it is not approved for general use in these conditions. As linezolid is unlikely to have cross-resistance with other antibiotics, because of its different mechanism of action, it should be reserved for organisms which are resistant to other antibiotics. As linezolid has oral formulations it may have a practical advantage over quinupristin/dalfopristin (see 'New drugs' Aust Prescr 2000;23:65), which is approved for the intravenous treatment of resistant organisms, but the two drugs have not been compared in clinical trials.