Drug interactions
Dextromethorphan + Fenfluramine
Severity: Major
Dextromethorphan and Fenfluramine: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Fenfluramine releases serotonin, and dextromethorphan inhibits serotonin reuptake, so combining them raises the risk of serotonin syndrome. Features include agitation, hyperreflexia, tremor, sweating and fever.
What this interaction means in plain words
Dextromethorphan and Fenfluramine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Dextromethorphan belongs to Respiratory; Fenfluramine belongs to Central Nervous System.
Why it happens
Additive serotonergic activity through serotonin release and reuptake inhibition.
What to do
Avoid concurrent use when possible, including over-the-counter cough products containing dextromethorphan. If used, monitor for serotonin syndrome and stop the agents if it occurs.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Dextromethorphan
- Dextromethorphan + Isocarboxazid Contraindicated
- Dextromethorphan + Linezolid Contraindicated
- Dextromethorphan + Phenelzine Contraindicated
- Dextromethorphan + Rasagiline Contraindicated
- Dextromethorphan + Safinamide Contraindicated
- Dextromethorphan + Selegiline Contraindicated
Other interactions of Fenfluramine
- Fenfluramine + Isocarboxazid Contraindicated
- Fenfluramine + Linezolid Contraindicated
- Fenfluramine + Phenelzine Contraindicated
- Fenfluramine + Selegiline Contraindicated
- Fenfluramine + Tranylcypromine Contraindicated
- Almotriptan + Fenfluramine Major
Frequently asked questions
Can I take Dextromethorphan with Fenfluramine?
MediHelp rates the interaction as major. Dextromethorphan and Fenfluramine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Fenfluramine releases serotonin, and dextromethorphan inhibits serotonin reuptake, so combining them raises the risk of serotonin syndrome. Features include agitation, hyperreflexia, tremor, sweating and fever.
How serious is the interaction between Dextromethorphan and Fenfluramine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid concurrent use when possible, including over-the-counter cough products containing dextromethorphan. If used, monitor for serotonin syndrome and stop the agents if it occurs.
What other medicines interact with Dextromethorphan?
MediHelp also lists interactions of Dextromethorphan with, for example, Isocarboxazid, Linezolid, Phenelzine. The full list is on the Dextromethorphan page.
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