Drug interactions
Fenfluramine + Isoniazid
Severity: Moderate
Fenfluramine and Isoniazid: moderate 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
Isoniazid has weak monoamine oxidase inhibiting activity, and fenfluramine increases serotonin release. In theory this could increase the risk of serotonin syndrome, although clinical reports are lacking.
What this interaction means in plain words
Fenfluramine and Isoniazid can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fenfluramine belongs to Central Nervous System; Isoniazid belongs to Anti Bacterial.
Why it happens
Weak MAO inhibition by isoniazid combined with fenfluramine-induced serotonin release.
What to do
Monitor for agitation, tremor, hyperthermia, clonus and autonomic instability when starting or increasing doses. Stop one agent if serotonin toxicity occurs.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Isoniazid
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 Isoniazid?
MediHelp rates the interaction as moderate. Fenfluramine and Isoniazid can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Isoniazid has weak monoamine oxidase inhibiting activity, and fenfluramine increases serotonin release. In theory this could increase the risk of serotonin syndrome, although clinical reports are lacking.
How serious is the interaction between Fenfluramine and Isoniazid?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for agitation, tremor, hyperthermia, clonus and autonomic instability when starting or increasing doses. Stop one agent if serotonin toxicity occurs.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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