Drug interactions
Fluvoxamine + Olanzapine / samidorphan
Severity: Major
Fluvoxamine and Olanzapine / samidorphan: 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
Fluvoxamine strongly inhibits CYP1A2, the main pathway of olanzapine clearance, and can substantially raise olanzapine concentrations. This may increase sedation, orthostatic hypotension, anticholinergic effects and metabolic or extrapyramidal adverse effects, with additive CNS depression.
What this interaction means in plain words
Fluvoxamine and Olanzapine / samidorphan 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.
Why it happens
Fluvoxamine inhibits CYP1A2-mediated olanzapine metabolism, with additional additive CNS depressant effects.
What to do
Start with a lower olanzapine dose and titrate according to response, monitoring sedation, blood pressure and tolerability. Reassess the dose if fluvoxamine is started or stopped.
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 Fluvoxamine
- Agomelatine + Fluvoxamine Contraindicated
- Alosetron + Fluvoxamine Contraindicated
- Fezolinetant + Fluvoxamine Contraindicated
- Fluvoxamine + Isocarboxazid Contraindicated
- Fluvoxamine + Mavacamten Contraindicated
- Fluvoxamine + Methylene blue Contraindicated
Frequently asked questions
Can I take Fluvoxamine with Olanzapine / samidorphan?
MediHelp rates the interaction as major. Fluvoxamine and Olanzapine / samidorphan 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. Fluvoxamine strongly inhibits CYP1A2, the main pathway of olanzapine clearance, and can substantially raise olanzapine concentrations. This may increase sedation, orthostatic hypotension, anticholinergic effects and metabolic or extrapyramidal adverse effects, with additive CNS depression.
How serious is the interaction between Fluvoxamine and Olanzapine / samidorphan?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Start with a lower olanzapine dose and titrate according to response, monitoring sedation, blood pressure and tolerability. Reassess the dose if fluvoxamine is started or stopped.
What other medicines interact with Fluvoxamine?
MediHelp also lists interactions of Fluvoxamine with, for example, Agomelatine, Alosetron, Fezolinetant. The full list is on the Fluvoxamine page.
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