Drug interactions
Levothyroxine + Primidone
Severity: Moderate
Levothyroxine and Primidone: 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
Primidone is metabolized to phenobarbital and induces hepatic enzymes, which can speed levothyroxine clearance. This may lower thyroid hormone levels and cause hypothyroid symptoms.
What this interaction means in plain words
Levothyroxine and Primidone 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.
Levothyroxine belongs to Endocrine; Primidone belongs to Central Nervous System.
Why it happens
Enzyme induction by primidone and its phenobarbital metabolite increases levothyroxine clearance.
What to do
Monitor TSH and free T4 after starting or stopping primidone, and raise the levothyroxine dose as needed.
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 Levothyroxine and Primidone, 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 Levothyroxine
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 Levothyroxine with Primidone?
MediHelp rates the interaction as moderate. Levothyroxine and Primidone 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. Primidone is metabolized to phenobarbital and induces hepatic enzymes, which can speed levothyroxine clearance. This may lower thyroid hormone levels and cause hypothyroid symptoms.
How serious is the interaction between Levothyroxine and Primidone?
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 TSH and free T4 after starting or stopping primidone, and raise the levothyroxine dose as needed.
What other medicines interact with Levothyroxine?
MediHelp also lists interactions of Levothyroxine with, for example, Cholestyramine, Sodium iodide i-131, Tiratricol. The full list is on the Levothyroxine 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.
