Rivaroxaban Concentration in Breast Milk During Breastfeeding: A Case Study

Oral direct factor Xa inhibitors, collectively referred to as direct oral anticoagulants, are not recommended for breastfeeding women due to insufficient data about the transfer of these drugs into breast milk. In this study, we serially measured rivaroxaban concentrations in the breast milk of one nursing mother who was at high risk of deep vein thrombosis and evaluated the health of her breastfed infant. Breast milk rivaroxaban concentrations were measured 3 months after delivery by a validated liquid chromatography-tandem mass spectrometry method. Breast milk samples were collected sequentially after 15 mg of oral rivaroxaban administration after ethical approval and informed consent. Case report: A 38-year-old female diagnosed with the antiphospholipid syndrome had received rivaroxaban after delivery. The infant was partially breastfed until the age of 18 months. The mean minimum and maximum rivaroxaban concentrations in breast milk were 9.73 ng/mL before each dose and 53.9 ng/mL at 6 hours after each dose, respectively. The mean daily infant dose was 0.0034 mg/kg and the mean relative infant dose (RID) via breast milk was 1.79%. The RIDs of rivaroxaban did not exceed 10% of the maternal dose, suggesting that exposure of rivaroxaban via breastfed is seldom clinically relevant for the infant. A pediatric assessment of the infant found no detectable drug-related adverse effects. Further studies are needed to elucidate how breastfeeding infants are impacted by exposure to rivaroxaban.