Drug interactions
Fosphenytoin + Rimegepant
Severity: Major
Fosphenytoin and Rimegepant: 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
Fosphenytoin is converted to phenytoin, a CYP3A4 inducer that can markedly lower rimegepant levels. Migraine treatment may fail.
What this interaction means in plain words
Fosphenytoin and Rimegepant 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.
Fosphenytoin belongs to Central Nervous System; Rimegepant belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 by phenytoin increases rimegepant metabolism.
What to do
Avoid concomitant use and choose an alternative acute migraine therapy.
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 Rimegepant
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Rimegepant?
MediHelp rates the interaction as major. Fosphenytoin and Rimegepant 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. Fosphenytoin is converted to phenytoin, a CYP3A4 inducer that can markedly lower rimegepant levels. Migraine treatment may fail.
How serious is the interaction between Fosphenytoin and Rimegepant?
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 concomitant use and choose an alternative acute migraine therapy.
What other medicines interact with Rimegepant?
MediHelp also lists interactions of Rimegepant with, for example, Amobarbital, Atazanavir, Butabarbital. The full list is on the Rimegepant page.
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