Spectrum of activity
Linezolid is effective against all clinically important Gram-positive bacteria—those whose cell wall contains a thick layer of peptidoglycan and no outer membrane—notably Enterococcus faecium and Enterococcus faecalis (including vancomycin-resistant enterococci), Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus, MRSA), Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes, the viridans group streptococci, Listeria monocytogenes, and Corynebacterium species (the latter being among the most susceptible to linezolid, with minimum inhibitory concentrations routinely below 0.5 mg/L). Linezolid is also highly active in vitro against several mycobacteria. It appears to be very effective against Nocardia, but because of high cost and potentially serious adverse effects, authors have recommended that it be combined with other antibiotics or reserved for cases that have failed traditional treatment.Linezolid is considered bacteriostatic against most organisms—that is, it stops their growth and reproduction without actually killing them—but has some bactericidal (killing) activity against streptococci. Some authors have noted that, despite its bacteriostatic effect in vitro, linezolid "behaves" as a bactericidal antibiotic in vivo because it inhibits the production of toxins by staphylococci and streptococci. It also has a post-antibiotic effect lasting one to four hours for most bacteria, meaning that bacterial growth is temporarily suppressed even after the drug is discontinued. Gram-negative bacteria
Linezolid has no clinically significant effect on most Gram-negative bacteria. Pseudomonas and the Enterobacteriaceae, for instance, are not susceptible. In vitro, it is active against Pasteurella multocida, Fusobacterium, Moraxella catarrhalis, Legionella, Bordetella, and Elizabethkingia meningoseptica, and moderately active (having a minimum inhibitory concentration for 90% of strains of 8 mg/L) against Haemophilus influenzae.
It is on the World Health Organizations List of Essential Medicines. The World Health Organization classifies linezolid as critically important for human medicine. Linezolid is available as a generic medication. Medical uses
The main use of linezolid is the treatment of severe infections caused by aerobic Gram-positive bacteria that are resistant to other antibiotics; it should not be used against bacteria that are sensitive to drugs with a narrower spectrum of activity, such as penicillins and cephalosporins. In both the popular press and the scientific literature, linezolid has been called a "reserve antibiotic"—one that should be used sparingly so that it will remain effective as a drug of last resort against potentially intractable infections.In the United States, the indications for linezolid use approved by the U.S. Food and Drug Administration (FDA) are the treatment of vancomycin-resistant Enterococcus faecium infections, with or without bacterial invasion of the bloodstream; nosocomial pneumonia (hospital-acquired) and community-acquired pneumonia caused by S. aureus or S. pneumoniae; complicated skin and skin structure infections (cSSSI) caused by susceptible bacteria, including diabetic foot infection, unless complicated by osteomyelitis (infection of the bone and bone marrow); and uncomplicated skin and soft tissue infections caused by S. pyogenes or S. aureus. The manufacturer advises against the use of linezolid for community-acquired pneumonia or uncomplicated skin and soft tissue infections caused by MRSA. In the United Kingdom, pneumonia and cSSSIs are the only indications noted in the product labeling.Linezolid appears to be as safe and effective for use in children and newborns as it is in adults.