Fondaparinux and Tibolone: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fondaparinux
Tibolone
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
Increased risk of bleeding
Interaction Deep Dive
Tibolone may increase blood fibrinolytic activity, and may enhance the effects of anticoagulants with concomitant use. Concomitant tibolone treatment led to enhanced warfarin-induced anticoagulation in healthy, postmenopausal women in a double-blind, randomized, placebo-controlled, 2-way crossover study. Use caution if coadministered, especially when starting or stopping concurrent tibolone treatment. If necessary, adjust the dose of the anticoagulant1.
Why it happens (mechanism)
Increase in blood fibrinolytic activity and enhanced anticoagulant effects
Literature reports
1 report — tap to read
a) In a double-blind, randomized, placebo-controlled, 2-way crossover study, concomitant tibolone treatment led to enhanced warfarin-induced anticoagulation in healthy, postmenopausal women. Subjects (n=16; age range, 50 to 65 years) who were stabilized on oral warfarin (dose range, 1 to 8.5 mg), with an INR ranging between 1.4 to 2.0, were randomized to receive either tibolone 2.5 mg/day for 21 days, followed by a 7-day washout period, and then followed by placebo treatment for 21 days (n=8); or vice versa (n=8). Warfarin treatment was continued during the washout period. Compared to placebo, tibolone treatment caused a statistically significant increase in the mean INR of 0.4. Among secondary efficacy parameters, coagulation factors II, VII, VIIa, and X were all statistically significantly lower during tibolone treatment compared to placebo. The estimated mean difference was -6.9% for Factor VIIa, and -31% for Factor VII. Significant interindividual differences were noted towards response in INR and coagulation factors during the 2 treatment periods. Overall, all treatments were well tolerated, with no clinically significant adverse events. While the exact mechanism for this interaction was unclear, competition for protein binding sites or pharmacodynamic causes were postulated as potential mechanisms 2.
Common questions
Can I take Fondaparinux and Tibolone together?
Increased risk of bleeding Always confirm with your pharmacist or prescriber before making any change.
How serious is the Fondaparinux and Tibolone 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.
Questions for your pharmacist
- Does my dose of Fondaparinux or Tibolone 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 (2)
- Product Information: Livial oral tablets, tibolone oral tablets. Merck Sharp & Dohme Limited (per eMC+), Hoddesdon, United Kingdom, 2015.
- Elbers J, Hageluken C, & Wadham A: Tibolone (Livial(R)) enhances warfarin-induced anticoagulation in postmenopausal women. Maturitas 2007; 56(1):94-100.
Keep reading about Fondaparinux
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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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