Drug interactions
Fenfluramine + Venlafaxine
Severity: Major
Fenfluramine and Venlafaxine: major interaction.
Last updated
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 venlafaxine blocks its reuptake, so combination can produce excess serotonergic activity. Serotonin syndrome can occur, with agitation, hyperthermia, clonus and autonomic instability.
What this interaction means in plain words
Fenfluramine and Venlafaxine 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 belongs to Central Nervous System; Venlafaxine belongs to Central Nervous System.
Why it happens
Additive serotonergic effects through serotonin release and reuptake inhibition.
What to do
Avoid combining if possible, or monitor closely for serotonin syndrome, especially at initiation and dose increases. Stop one or both agents if symptoms occur.
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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Other interactions of Venlafaxine
- Isocarboxazid + Venlafaxine Contraindicated
- Methylene blue + Venlafaxine Contraindicated
- Phenelzine + Venlafaxine Contraindicated
- Procarbazine + Venlafaxine Contraindicated
- Rasagiline + Venlafaxine Contraindicated
- Safinamide + Venlafaxine 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 Fenfluramine with Venlafaxine?
MediHelp rates the interaction as major. Fenfluramine and Venlafaxine 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 venlafaxine blocks its reuptake, so combination can produce excess serotonergic activity. Serotonin syndrome can occur, with agitation, hyperthermia, clonus and autonomic instability.
How serious is the interaction between Fenfluramine and Venlafaxine?
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 combining if possible, or monitor closely for serotonin syndrome, especially at initiation and dose increases. Stop one or both agents if symptoms occur.
What other medicines interact with Venlafaxine?
MediHelp also lists interactions of Venlafaxine with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Venlafaxine page.
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