Coumadin with the birth control pill
Many women of reproductive age take a combined or progestogen-only oral contraceptive while also using a chronic medication such as Coumadin (Warfarin). The combination is generally fine at 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, 10mg, but a small number of medications can reduce contraceptive efficacy meaningfully and need either a backup method or a switch.
How Coumadin can affect contraceptive efficacy
Combined and progestogen-only contraceptives are metabolised through CYP3A4. Strong CYP3A4 inducers (some antiepileptics, rifampicin, St John's Wort) lower contraceptive plasma levels and reduce efficacy. Whether Warfarin acts on CYP3A4 determines whether Coumadin affects contraception. Most agents in Cardiovascular Medications have no clinically meaningful effect on the pill at 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, 10mg.
Practical guidance
According to the prescribing information for Warfarin, women on hormonal contraception should review Coumadin with the prescribing pharmacist or doctor. Where an interaction is documented, additional barrier contraception or switching to a non-oral method (IUD, implant) for the duration of Coumadin therapy is the standard mitigation.
Frequently asked questions
Will Coumadin make my pill less effective? ▾
Most Cardiovascular Medications medications at 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, 10mg do not affect oral contraceptive efficacy. The exceptions are CYP3A4-inducing drugs and a small number of others. The prescribing information for Warfarin states whether the interaction is meaningful.
Do I need a backup contraceptive on Coumadin? ▾
Backup contraception is needed only when there is a documented interaction between Coumadin and the contraceptive method. For most users at 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, 10mg, no backup is required. The pharmacist confirms whether Warfarin interacts with hormonal contraception.
More on Coumadin
- With alcoholCoumadin and alcohol — is it safe to drink?
- With foodShould Coumadin be taken with food?
- Side effectsCoumadin side effects: common, rare and warning signs
- Dosage guideCoumadin dosage guide: how much to take and when
- OnsetHow fast does Coumadin start working?
- DurationHow long does Coumadin last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.