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Linezolid, serious CNS reactions possible when given to patients taking serotonergic psychiatric drugs

The FDA ( Food and Drug Administration ) has updated information on the potential drug interaction between Linezolid ( Zyvox; in Europe: Zyvoxid ) and serotonergic psychiatric medications.
Not all serotonergic psychiatric drugs have an equal capacity to cause serotonin syndrome with Linezolid. Most cases from the Adverse Event Reporting System ( AERS ) of serotonin syndrome with Linezolid occurred in patients taking specific serotonergic psychiatric drugs, namely a selective serotonin reuptake inhibitor ( SSRI ) or a serotonin norepinephrine reuptake inhibitor ( SNRI ).
It is unclear at this time whether Linezolid administration in patients receiving other psychiatric drugs with lesser degrees of serotonergic activity poses a comparable risk.

Linezolid is used to treat infections, including pneumonia, infections of the skin, and infections caused by a resistant bacterium ( Enterococcus faecium ).
It is a reversible monoamine oxidase inhibitor ( MAOI ). Although the exact mechanism of this drug interaction is unknown, Linezolid inhibits the action of monoamine oxidase A, an enzyme responsible for breaking down serotonin in the brain. It is believed that when Linezolid is given to patients taking serotonergic psychiatric medications, high levels of serotonin can build up in the brain, causing toxicity. This is referred to as serotonin syndrome; signs and symptoms include mental changes ( confusion, hyperactivity, memory problems ), muscle twitching, excessive sweating, shivering or shaking, diarrhea, trouble with coordination and/or fever.

Linezolid should generally not be given to patients taking serotonergic drugs. However, there are some conditions that may be life-threatening or require urgent treatment with Linezolid such as when: Linezolid is used to treat Vancomycin-resistant Enterococcus faecium ( VRE ) infections; Linezolid is used to treat infections such as nosocomial pneumonia and complicated skin and skin structure infections, including cases caused by Methicillin-resistant Staphylococcus aureus ( MRSA ).

Source: FDA, 2011