Oxazolidinones

Agent: linezolid

Currently, linezolid is the only available member of the oxazolidinone class. Thanks to its broad Gram-positive activity and excellent oral bioavailability,  linezolid has become a useful (albeit expensive) antibiotic for the treatment of various resistant Gram-positive infections. Its use is likely to increase as MRSA becomes more prevalent in the community,  but remember that other drugs can combat MRSA infections as well.

Spectrum

Good: MSSA, MRSA, streptococci (including multidrug-resistant S. pneumoniae), enterococci  (including VRE), Nocardia

Moderate: some atypicals

Poor : all Gram-negatives, anaerobes

Adverse Effects

Linezolid is generally well tolerated, but it can cause bone marrow suppression, most commonly thrombocytopenia. Bone marrow suppression tends to occur after 2 or more weeks of therapy and war-rants monitoring. Peripheral neuropathy may occur after even more prolonged therapy (months)  because of toxicity to mitochondria.

Important Facts

• Linezolid has bioavailability approaching 100%,and its oral formulation greatly increases its utility.

• Linezolid is also an inhibitor of monoamine oxidase and can cause serotonin syndrome when given concurrently with serotonergic agents such as selective serotonin reuptake inhibitors  (SSRIs)—avoid concurrent use if possible. Re-cent evidence has shown this reaction to be un-common, but it does occur. The interaction is listed as a contraindication in linezolid’s pack-age insert.

• Linezolid has dual hepatic and renal elimination, and doses do not need to be adjusted in cases of renal or hepatic dysfunction.

• Both oral and IV formulations are very expensive, but the oral formulation is less expensive than home-infusion vancomycin and a nurse.

What It’s Good For

Infections caused by resistant Gram-positive organ-isms such as MRSA and VRE, including nosocomial pneumonia and skin and soft-tissue infections.

Don’t Forget!

Monitor patients for bone marrow suppression,  particularly during long-term therapy with linezolid. Avoid concurrent serotonergic drug use if possible. Remember that many SSRIs have long half-lives, so simply discontinuing SSRI use does not avoid a potential interaction. Monitor patients for signs and symptoms of serotonin syndrome if the interaction cannot be avoided.

References

Gallagher ,J.C. and MacDougall ,c. (2012). Antibiotics Simplified. Second Edition. Jones & Bartlett Learning, LLC.