Breastfeeding mothers taking tacrolimus do not pass the immunosuppressant on to their babies when breastfeeding, study results show.
The good news for breastfeeding mothers is that ingestion of tacrolimus by infants via breast milk is "negligible," say the researchers.
"Although more studies are required to confirm drug safety, our findings suggest that women taking tacrolimus who wish to breastfeed after appropriate counseling should not be discouraged from doing so," said lead researcher Kate Bramham (King's College, London, UK) in a press statement.
Published in the Clinical Journal of the American Society of Nephrology, the study addresses the concern among physicians and mothers that breastfeeding while taking tacrolimus could expose the baby to the drug and adversely impair the developing immune system.
Investigators recruited 14 women and their 15 infants to study tacrolimus levels in breast milk and the subsequent exposure of the babies to this drug during breastfeeding. Of the 15 babies, two of whom were breastfed by one mother, 11 were exclusively fed breast milk.
All the infants assessed had a decline in tacrolimus levels of approximately 15% per day. Eight of the infants had undetectable levels of tacrolimus by day 14.
The breastfed infants did not have higher levels of tacrolimus when compared with infants who were fed by bottle.
The infant dose of tacrolimus, which was based on the highest breast-milk concentration, was estimated to be 0.56 µg/d, or the equivalent of 0.23% of the maternal dose.
"This is the largest study to report serial tacrolimus blood levels in neonates, together with breast milk analysis, and suggests that initial detectable levels are the consequence of placental transfer, rather than ingestion via breast milk," report Bramham and colleagues.
The decline in tacrolimus levels in the breastfed and bottle-fed infants, along with undetectable levels in eight infants at day 14, suggests that tacrolimus transfer in breast milk is minimal, say the researchers.
While infants of mothers receiving tacrolimus in pregnancy might be born with significant levels of the drug, they are exposed to minimal amounts of tacrolimus if breastfed, they conclude.
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