Linezolid ( Zyvoxam ), a synthetic antibacterial agent in a new class of antibiotics, the oxazolidinones, has been marketed in Canada since Apr. 6, 2001.Linezolid is active against methicillin- and vancomycin-resistant gram-positive microorganisms.

The safety and efficacy of linezolid given for longer than 28 days have not been evaluated in controlled clinical trials. Dosage and administration guidelines recommend that treatment last no more than 28 consecutive days. Because of its activity against resistant organisms that cause osteomyelitis and prosthetic joint infections, linezolid has been used in clinical practice for longer than the recommended treatment course.

The long-term use of linezolid has been associated with severe peripheral and optic neuropathy. In most cases the optic neuropathy resolved after stopping the drug, but the peripheral neuropathy did not.

Health Canada has received a report of a 71-year-old woman who received linezolid, 600 mg twice daily, for an acquired methicillin-resistant Staphylococcus aureus (MRSA) infection. The patient received an initial 6-week course of linezolid, stopped treatment for 4–5 months and was given the drug again for 8 months. Linezolid was stopped when the patient was admitted to hospital with anemia, pure red cell aplasia and severe peripheral neuropathy. She had initially noticed numbness in her feet a month previously. At the time of the report, the anemia had resolved but the neuropathy had not. Novo-Hydrazide was also considered a suspect drug.

Neuropathy ( peripheral or optic ) has rarely been reported in patients treated with linezolid and has primarily occurred in patients treated for more than the maximum recommended duration of 28 days. Myelosuppression including anemia is listed in the product monograph under warnings and postmarketing experience. Pure red cell aplasia is not listed in the product monograph.

Health care professionals must be aware of the potential for serious adverse reactions, including neuropathy, when linezolid is used beyond its recommended duration.

Source : Health Canada, 2005

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