Drug interactions
Propylthiouracil + Warfarin
Severity: Moderate
Propylthiouracil and Warfarin: 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
Treating hyperthyroidism changes the clearance of vitamin K-dependent clotting factors, so as patients become euthyroid the warfarin response is reduced and the INR may fall. Propylthiouracil itself may also rarely cause hypoprothrombinemia.
What this interaction means in plain words
Propylthiouracil and Warfarin 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.
Propylthiouracil belongs to Endocrine; Warfarin belongs to Cardiovascular.
Why it happens
Correcting hyperthyroidism slows clotting factor catabolism, decreasing warfarin sensitivity.
What to do
Monitor INR frequently as thyroid status normalizes and increase the warfarin 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?
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Other interactions of Warfarin
- Defibrotide + Warfarin Contraindicated
- Ketorolac + Warfarin Contraindicated
- Abciximab + Warfarin Major
- Acetylsalicylic acid + Warfarin Major
- Adagrasib + Warfarin Major
- Amiodarone + Warfarin Major
Other interactions of Propylthiouracil
Frequently asked questions
Can I take Propylthiouracil with Warfarin?
MediHelp rates the interaction as moderate. Propylthiouracil and Warfarin 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. Treating hyperthyroidism changes the clearance of vitamin K-dependent clotting factors, so as patients become euthyroid the warfarin response is reduced and the INR may fall. Propylthiouracil itself may also rarely cause hypoprothrombinemia.
How serious is the interaction between Propylthiouracil and Warfarin?
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 INR frequently as thyroid status normalizes and increase the warfarin dose as needed.
What other medicines interact with Warfarin?
MediHelp also lists interactions of Warfarin with, for example, Defibrotide, Ketorolac, Abciximab. The full list is on the Warfarin page.
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