Product Liability

New contraindications for psychiatric serotonin drugs

The Food and Drug Administration (FDA) issued warnings about two separate drugs interacting with psychiatric drugs that work through the serotonin system of the brain, such as selective serotonin reuptake inhibitors (SSRIs) and psychedelic drugs. When these drugs are combined with certain types of psychiatric drugs, serious central nervous system reactions can occur.

The FDA warnings include the antibacterial drug linezolid (Zyvox) and the drug methylene blue. Zyvox is used to treat bacterial infections including pneumonia, infections of the skin, and infections resistant to other antibiotics. It is a reversible monoamine oxidase inhibitor (MAOI).

Methylene blue is used to treat methemoglobinemia, vasoplegic syndrome, ifosfamide-induced encephalopathy, and cyanide poisoning. It is also used as a dye in therapeutic and diagnostic applications. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI).

Although the exact mechanism of these drugs’ interaction is unknown, Zyvox and methylene blue each inhibit the action of monoamine oxidase A — an enzyme responsible for breaking down serotonin in the brain.

It is believed that when either of these drugs are 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.

The FDA recommends that Zyvox and methylene blue not be given to patients taking serotonergic drugs. However, there are conditions that may be life-threatening or require urgent treatment with either Zyvox or methylene blue. In the meantime, patients should not stop taking their serotonergic psychiatric medicine without first talking to their doctors.

Any side effects with these or any medications should be reported to the FDA MedWatch Adverse Event Reporting Program at