Drug interactions
Flibanserin + Phenytoin
Severity: Major
Flibanserin and Phenytoin: 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
Phenytoin is a strong CYP3A4 inducer. It would be expected to reduce flibanserin concentrations substantially, making it ineffective.
What this interaction means in plain words
Flibanserin and Phenytoin 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.
Flibanserin belongs to Genitourinary; Phenytoin belongs to Central Nervous System.
Why it happens
CYP3A4 induction by phenytoin increases flibanserin clearance.
What to do
Avoid the combination, since flibanserin labeling advises against strong CYP3A4 inducers. Choose an alternative if an anticonvulsant is required.
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 Flibanserin
- Atazanavir + Flibanserin Contraindicated
- Ceritinib + Flibanserin Contraindicated
- Clarithromycin + Flibanserin Contraindicated
- Cobicistat + Flibanserin Contraindicated
- Conivaptan + Flibanserin Contraindicated
- Crizotinib + Flibanserin Contraindicated
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Flibanserin with Phenytoin?
MediHelp rates the interaction as major. Flibanserin and Phenytoin 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. Phenytoin is a strong CYP3A4 inducer. It would be expected to reduce flibanserin concentrations substantially, making it ineffective.
How serious is the interaction between Flibanserin and Phenytoin?
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 the combination, since flibanserin labeling advises against strong CYP3A4 inducers. Choose an alternative if an anticonvulsant is required.
What other medicines interact with Flibanserin?
MediHelp also lists interactions of Flibanserin with, for example, Atazanavir, Ceritinib, Clarithromycin. The full list is on the Flibanserin page.
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