Is Warfarin (anticoagulant) safe to use during breastfeeding?

Warfarin Safety During Breastfeeding

Warfarin is safe to use during breastfeeding and is recommended as one of the preferred anticoagulants for breastfeeding women who require anticoagulation therapy. 1

Pharmacological Properties Supporting Safety

• Warfarin has properties that limit its transfer into breast milk:

  • It is polar and nonlipophilic
  • It is highly protein-bound in maternal circulation
  • These characteristics make it unlikely to be excreted in significant amounts into breast milk 1

• Studies have demonstrated minimal to no detection of warfarin in breast milk:

  • A study of 13 women found no detectable drug levels in breast milk (to a level of 0.08 mmol/L) or infant plasma 1, 2
  • Multiple observational studies of breastfeeding women taking warfarin failed to identify any cases of infant bleeding 1

Clinical Evidence and Guidelines

• The American Society of Hematology (ASH) 2018 guidelines strongly recommend warfarin as a safe option for breastfeeding women requiring anticoagulation 1

• Warfarin is specifically listed among the preferred agents with the best evidence for safety in breastfeeding, along with acenocoumarol and LMWH 1

• The FDA drug label for warfarin notes: "Based on very limited published data, warfarin has not been detected in the breast milk of mothers treated with warfarin" 3

Monitoring Recommendations

• While warfarin is considered safe during breastfeeding, monitoring is still advised:

  • The FDA recommends that "women who are breast-feeding and anticoagulated with warfarin should be very carefully monitored so that recommended PT/INR values are not exceeded" 3

• It is prudent to:

  • Perform coagulation tests in infants if concerns arise
  • Evaluate vitamin K status in infants before advising women taking warfarin to breastfeed 3
  • Monitor the infant for any unusual symptoms such as changes in stool pattern, irritability, or poor feeding 4

Dosing Considerations

• Postpartum women who are breastfeeding may require higher warfarin doses compared to their pre-pregnancy requirements:
  • Case reports suggest some women may need up to 100% increase in warfarin dose postpartum to achieve therapeutic INR while breastfeeding 5
  • Close monitoring and appropriate dose adjustments are necessary during this period 5

Comparison with Other Anticoagulants

• Warfarin, acenocoumarol, and LMWH are the agents with greatest experience and best evidence for safety in breastfeeding women 1

• Direct-acting oral anticoagulants (DOACs) should be avoided during breastfeeding:

  • ASH guidelines strongly recommend against using DOACs in breastfeeding women 1, 6
  • Limited data exists on their excretion into breast milk and potential effects on infants 1

Clinical Decision Making

• When choosing between safe anticoagulant options for breastfeeding women, consider:

  • Drug efficacy for the specific indication
  • Strength of evidence for safety
  • Patient preference regarding subcutaneous injections (LMWH) versus oral medication (warfarin)
  • Patient ability to attend regular INR monitoring if warfarin is chosen 1

• Both heparins and warfarin are considered safe options during breastfeeding, with the choice depending on the specific clinical situation and patient factors 6