Linezolid: an oxazolidinone antimicrobial agent.

BACKGROUND: Linezolid is the first oxazolidinone anti-infective agent marketed in the United States. It is indicated for the treatment of nosocomial pneumonia, complicated skin and skin-structure infections caused by methicillin-sensitive or methicillin-resistant Staphylococcus aureus and other susceptible organisms, and vancomycin-resistant Enterococcus faecium infections. It also is indicated for the treatment of uncomplicated skin and skin-structure infections caused by methicillin-sensitive S. aureus or Streptococcus pyogenes, and community-acquired pneumonia caused by penicillin-sensitive Streptococcus pneumoniae. OBJECTIVE: This article reviews the pharmacologic properties and clinical usefulness of linezolid. METHODS: Using the terms linezolid, PNU-100766, and oxazolidinone, we performed a literature search of the following databases: MEDLINE (1966 to September 2000), HealthSTAR (1993 to September 2000), Iowa Drug Information Service (1966 to September 2000), International Pharmaceutical Abstracts (1970 to September 2000), PharmaProjects (January 2000 version), and meeting abstracts of the Infectious Diseases Society of America and the Interscience Conference on Antimicrobial Agents and Chemotherapy (1996 to 2000). RESULTS: Linezolid has a unique structure and mechanism of action, which targets protein synthesis at an exceedingly early stage. Consequently, cross-resistance with other commercially available antimicrobial agents is unlikely. It is primarily effective against gram-positive bacteria. To date, resistance to linezolid has been reported in patients infected with enterococci. The pharmacokinetic parameters of linezolid in adults are not altered by hepatic or renal function, age, or sex to an extent requiring dose adjustment. Linezolid is metabolized via morpholine ring oxidation, which is independent of the cytochrome P450 (CYP450) enzyme system; as a result, linezolid is unlikely to interact with medications that stimulate or inhibit CYP450 enzymes. Compassionate-use trials and other clinical studies involving mainly adult hospitalized patients with gram-positive infections have shown that linezolid administered intravenously or orally is effective in a variety of nosocomial and community-acquired infections, including those caused by resistant gram-positive organisms. Reported adverse effects include thrombocytopenia. diarrhea, headache, nausea, vomiting, insomnia, constipation, rash, and dizziness. Preliminary pharmacoeconomic data indicate that a significantly higher percentage of patients receiving linezolid therapy versus comparator could be discharged from the hospital by day 7 (P = 0.005). CONCLUSIONS: Linezolid appears to be effective while maintaining an acceptable tolerability profile. Due to the risk of bacterial resistance, linezolid should be reserved for the treatment of documented serious vancomycin-resistant enterococcal infections.