From the Guidelines
Dextromorphan should not be used with monoamine oxidase inhibitors (MAOIs) due to the risk of serotonin syndrome, a potentially life-threatening condition. The combination of these two substances can lead to excessive serotonin accumulation in the brain, causing symptoms like agitation, confusion, high fever, muscle rigidity, and seizures 1. Patients taking MAOIs such as phenelzine, tranylcypromine, isocarboxazid, or selegiline should avoid dextromethorphan completely and wait at least 14 days after stopping an MAOI before using any medication containing dextromethorphan. Some key points to consider when dealing with MAOIs and dextromethorphan include:
- The risk of serotonin syndrome is high when combining these two substances, and it can be life-threatening 1
- Alternative non-dextromethorphan cough suppressants such as benzonatate or guaifenesin may be used after consulting with a healthcare provider
- It is essential to check medication labels for dextromethorphan (often listed as "DM") and inform all healthcare providers about MAOI therapy to prevent dangerous interactions
- The symptoms of serotonin syndrome can arise within 24 to 48 hours after combining medications and are characterized by mental status changes, neuromuscular hyperactivity, and autonomic hyperactivity 1.
From the FDA Drug Label
Warnings Do not use if you are now taking a prescription monoamine oxidase inhibitor (MAOI) (certain drugs for depression, psychiatric or emotional conditions, or Parkinson’s disease), or for 2 weeks after stopping the MAOI drug. The combination of dextromorphan and MAOI is contraindicated.
- Do not use dextromorphan if you are taking an MAOI.
- Wait for 2 weeks after stopping the MAOI before taking dextromorphan 2.
From the Research
Dextromorphan and MAOI Interaction
- There is limited information available on the interaction between dextromorphan and monoamine oxidase inhibitors (MAOIs) in the provided studies.
- Dextromorphan is a cough suppressant that acts on the central nervous system, while MAOIs are a class of antidepressants that inhibit the action of monoamine oxidase, an enzyme involved in the breakdown of certain neurotransmitters 3.
- The use of MAOIs with other medications, including cough suppressants, is generally cautioned due to the risk of adverse interactions, such as serotonin syndrome or hypertensive crisis 4, 5, 6.
- However, there is no specific information available in the provided studies on the interaction between dextromorphan and MAOIs.
- Studies have examined the use of MAOIs in combination with other antidepressants or stimulants for the management of treatment-resistant depression, and have found that cautious use of these combinations may be effective under close supervision 4.
- Additionally, studies have investigated the efficacy of cough suppressants, including dextromorphan, in relieving cough symptoms, but have not specifically addressed the interaction between dextromorphan and MAOIs 3, 7.