Warfarin dosage in a postpartum woman while breastfeeding: A case report

Warfarin is the only oral anticoagulant recommended in women who are breastfeeding. Although warfarin is a compatible and recommended agent in the postpartum period and during lactation, little is known regarding changes to warfarin dose requirements in this patient population. Here, we report the case of a 40-year-old woman who transitioned from enoxaparin monotherapy back to warfarin at 2 months postpartum, while she was breastfeeding. Despite resuming warfarin at her previously therapeutic dose, her international normalized ratio (INR) remained subtherapeutic and required multiple dose increases. She ultimately required a 100% increase in her warfarin dose postpartum, compared to pre-pregnancy, to achieve a therapeutic INR. This case suggests patients may require higher warfarin doses postpartum, compared to pre-pregnancy, especially if breastfeeding. Clinicians should closely monitor these patients and adjust warfarin doses as necessary.