Drug interactions
Buprenorphine long-acting + Phenytoin
Severity: Moderate
Buprenorphine long-acting and Phenytoin: 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
Phenytoin is a strong inducer of CYP3A4 and can lower buprenorphine concentrations. Reduced exposure may cause inadequate opioid effect, breakthrough symptoms or withdrawal. Because the long-acting injection cannot be titrated quickly, the problem may persist for weeks.
What this interaction means in plain words
Buprenorphine long-acting and Phenytoin 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.
Why it happens
Induction of CYP3A4 by phenytoin increases the metabolism of buprenorphine.
What to do
Monitor for withdrawal symptoms, cravings and clinical response if the injection is used with phenytoin. If dosing proves inadequate and phenytoin cannot be changed, return to a transmucosal buprenorphine formulation that allows dose adjustment.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Buprenorphine long-acting and Phenytoin, 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.
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 Buprenorphine long-acting with Phenytoin?
MediHelp rates the interaction as moderate. Buprenorphine long-acting and Phenytoin 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. Phenytoin is a strong inducer of CYP3A4 and can lower buprenorphine concentrations. Reduced exposure may cause inadequate opioid effect, breakthrough symptoms or withdrawal. Because the long-acting injection cannot be titrated quickly, the problem may persist for weeks.
How serious is the interaction between Buprenorphine long-acting and Phenytoin?
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 withdrawal symptoms, cravings and clinical response if the injection is used with phenytoin. If dosing proves inadequate and phenytoin cannot be changed, return to a transmucosal buprenorphine formulation that allows dose adjustment.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin 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.
