Does warfarin administration to nursing mothers result in detectable warfarin levels or altered coagulation in their breast-fed infants?
Warfarin does not pass into breast milk in clinically significant amounts and is undetectable in breast-fed infants, suggesting it is safe for use in nursing mothers.
Warfarin was measured with a sensitive and specific method in the plasma and breast milk of 13 mothers. Less than 0-08 micronmol warfarin per litre (25 ng/ml) of breast milk was found in each instance. Seven of the mothers were breast-feeding their infants, in none of whom was warfarin detected in the plasma; furthermore, in three the British corrected ratio of the plasma was appreciably less than that of the mother and was within the expected range. We conclude that nursing mothers given warfarin may safely breast-feed their infants.
Orme et al. (1977) studied this question.