letrozole vs warfarin
Side-by-side comparison of letrozole and warfarin. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
minor Known Drug Interaction
Warfarin An interaction study (P017) with warfarin showed no clinically significant effect of letrozole on warfarin pharmacokinetics.
Recommendation: You can usually take these together without any changes, but keep following your doctor's plan for blood tests.
Letrozole is a medicine that lowers estrogen levels in women after menopause. It is used to treat breast cancer that is affected by hormones.
Warfarin is a medicine that helps prevent blood clots. It is used to treat and prevent dangerous clots from forming in your body.
Letrozole is used to treat breast cancer in women who have gone through menopause. It can be used as an initial treatment, after other treatments like tamoxifen, or when the cancer has spread. It works best for cancers that are hormone receptor positive or when the hormone receptor status is unknown.
Warfarin is used to prevent and treat blood clots in your veins and lungs. It can also prevent clots if you have atrial fibrillation (irregular heartbeat) or a replacement heart valve. After a heart attack, it can lower the risk of death, another heart attack, or a stroke.
Letrozole blocks a protein called aromatase in the body. Aromatase makes estrogen. By blocking aromatase, letrozole lowers the amount of estrogen, which can slow or stop the growth of breast cancer cells that need estrogen to grow.
Warfarin works by blocking your body's use of vitamin K. Vitamin K is needed to make blood clotting factors. By blocking vitamin K, warfarin makes your blood less likely to clot.
- • Hot flashes
- • Joint pain
- • Flushing
- • Weakness
- • Swelling
- • Bleeding from any tissue or organ
- Tiredness 7,158
- Feeling sick to your stomach 5,259
- Low white blood cell count 4,896
- Loose stools 4,460
- Cancer getting worse 4,253
- INR increased 10,275
- Shortness of breath 8,408
- Interaction with another medicine 6,289
- Tiredness 6,141
- Feeling sick to your stomach 5,921
Letrozole can cause bone thinning, which may lead to fractures. Your doctor may monitor your bone density. Letrozole can also harm an unborn baby, so you must not take it if you are pregnant. Use effective birth control if you could become pregnant.
Warfarin can cause major or fatal bleeding. You must have your blood tested regularly (INR) while taking warfarin. Many things, like other medicines and diet changes, can affect your INR. Tell your doctor about any bleeding and follow their instructions to prevent bleeding.
Do not take letrozole if you are pregnant because it can harm your unborn baby. If there is any chance you could become pregnant, use birth control while taking letrozole. Do not breastfeed while taking letrozole.
Warfarin can harm your unborn baby, especially during the first three months of pregnancy. Do not take warfarin if you are pregnant, unless you have a mechanical heart valve and your doctor says the benefits outweigh the risks. Talk to your doctor if you are breastfeeding, and watch your baby for bruising or bleeding.
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How to Read This letrozole vs warfarin Comparison
letrozole is classified in the Aromatase Inhibitor drug class, while warfarin sits within the Vitamin K Antagonist (Anticoagulant) class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are prescription-only, so a licensed provider must authorize use.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, letrozole has 26,026 submissions while warfarin has 37,034. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known minor interaction flagged in FDA labeling, attributed to research shows that letrozole does not change how the body handles the blood thinner warfarin. there is no major interaction between these two drugs.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between letrozole and warfarin - always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.