Etofenamate and Levothyroxine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Levothyroxine
Etofenamate
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Transient increase in FT4 followed by decrease in serum T4 and normal FT4 and TSH levels
Interaction Deep Dive
Coadministration of heparin with fenamates results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations. Closely monitor thyroid hormone parameters with concomitant use of levothyroxine and fenamates1.
Why it happens (mechanism)
Displacement of protein-binding site of levothyroxine by fenamates
Common questions
Can I take Etofenamate and Levothyroxine together?
Transient increase in FT4 followed by decrease in serum T4 and normal FT4 and TSH levels Always confirm with your pharmacist or prescriber before making any change.
How serious is the Etofenamate and Levothyroxine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Etofenamate or Levothyroxine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Product Information: TIROSINT(R)-SOL oral solution, levothyroxine sodium oral solution. IBSA Pharma Inc. (per FDA), Parsippany, NJ, 2023. DailyMed
Keep reading about Levothyroxine
Keep reading about Etofenamate
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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