Drug interactions
Phenytoin + Ramelteon
Severity: Moderate
Phenytoin and Ramelteon: 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 an inducer of CYP3A4 and other enzymes, and can reduce ramelteon concentrations. This may lead to loss of hypnotic effect, as seen with strong inducers like rifampin.
What this interaction means in plain words
Phenytoin and Ramelteon 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 belongs to Central Nervous System; Ramelteon belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and CYP1A2, increasing the hepatic clearance of ramelteon.
What to do
Monitor for reduced efficacy of ramelteon and consider an alternative hypnotic if insomnia is not controlled.
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 Phenytoin and Ramelteon, 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 Ramelteon
- Calcium / magnesium / potassium / sodium oxybates + Ramelteon Contraindicated
- Fluvoxamine + Ramelteon Contraindicated
- Ramelteon + Sodium oxybate Contraindicated
- Alfentanil + Ramelteon Moderate
- Amitriptyline + Ramelteon Moderate
- Amobarbital + Ramelteon Moderate
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 Phenytoin with Ramelteon?
MediHelp rates the interaction as moderate. Phenytoin and Ramelteon 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 an inducer of CYP3A4 and other enzymes, and can reduce ramelteon concentrations. This may lead to loss of hypnotic effect, as seen with strong inducers like rifampin.
How serious is the interaction between Phenytoin and Ramelteon?
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 reduced efficacy of ramelteon and consider an alternative hypnotic if insomnia is not controlled.
What other medicines interact with Ramelteon?
MediHelp also lists interactions of Ramelteon with, for example, Calcium / magnesium / potassium / sodium oxybates, Fluvoxamine, Sodium oxybate. The full list is on the Ramelteon 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.
