Drug interactions
Primidone + Ulipristal
Severity: Major
Primidone and Ulipristal: 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
Primidone is metabolized to phenobarbital, a CYP3A4 inducer, and may lower ulipristal exposure, risking emergency contraception failure.
What this interaction means in plain words
Primidone and Ulipristal 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
Primidone and its phenobarbital metabolite induce CYP3A4, increasing ulipristal clearance.
What to do
Avoid ulipristal and use a copper intrauterine device. Induction may persist for weeks after stopping primidone.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Primidone and Ulipristal, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
References
Other interactions of Primidone
- Lorlatinib + Primidone Contraindicated
- Lurasidone + Primidone Contraindicated
- Primidone + Ranolazine Contraindicated
- Primidone + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
- Primidone + Voriconazole Contraindicated
- Abiraterone + Primidone Major
Frequently asked questions
Can I take Primidone with Ulipristal?
MediHelp rates the interaction as major. Primidone and Ulipristal 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. Primidone is metabolized to phenobarbital, a CYP3A4 inducer, and may lower ulipristal exposure, risking emergency contraception failure.
How serious is the interaction between Primidone and Ulipristal?
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 ulipristal and use a copper intrauterine device. Induction may persist for weeks after stopping primidone.
What other medicines interact with Primidone?
MediHelp also lists interactions of Primidone with, for example, Lorlatinib, Lurasidone, Ranolazine. The full list is on the Primidone page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
