Women taking the immunosuppressant tacrolimus can rest assured that breast feeding will not elevate their babies' exposure to the drug, according to a study appearing in an upcoming issue of the Clinical Journal of the American Society of Nephrology (CJASN). The findings are good news for young women who have received an organ transplant in the past or who are taking the drug for other reasons.
Women taking the tacrolimus have previously been advised not to breast feed due to the possibility that the drug might be transferred to the baby, which could potentially suppress the baby's developing immune system. While there are many benefits to breast-feeding, there is very little known about the safety of breast-feeding while taking tacrolimus.
Kate Bramham, MRCP (King's College London) and her colleagues looked to determine the extent to which tacrolimus is transferred to infants via breast milk. Fourteen women taking tacrolimus during pregnancy and lactation, and their 15 infants (11 of whom were exclusively breast-fed) were assessed.
Among the major findings:
• Babies born to mothers taking tacrolimus had high levels of the drug in their blood at birth, likely due to transfer across the placenta, but the levels fell as the liver cleared the drug.
• Both babies who were breast-fed and those who were bottle-fed cleared the drug at the same rate. Most cleared the drug by two weeks.
• The breast milk of mothers taking tacrolimus contained only very low levels of the drug. (If babies were to take the same amount of tacrolimus per kilogram of body weight as their mothers, they would need to consume approximately 150 liters of breast milk per day.)
"Our study shows that levels of the drug are not significantly increased through breast feeding. Although more studies are needed on the safety of tacrolimus, the findings would suggest that women who wish to breastfeed should not be discouraged from doing so," said Dr. Bramham. "The advantages, particularly in preterm infants, need to be weighed against the theoretical disadvantages of minimal ingestion through breast milk," she added. Of note, women who have received a kidney transplant in the past are more likely to have early deliveries.
Study co-authors include Gary Chusney, Janet Lee PhD, Liz Lightstone, PhD, FRCP, and Catherine Nelson-Piercy, FRCP, FRCOG.
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