Background: Cyclosporine is known to be excreted in breast milk, but levels in infants are not known. Post-transplant breast-feeding has been contraindicated in mothers treated with calcineurin inhibitors such as cyclosporine.
Case: A 35-year-old woman exclusively breast-fed her infant during the first 10.5 months of life while she was being treated with cyclosporine. Cyclosporine measurements in infant and maternal blood and breast milk revealed a mean breast milk/maternal blood level ratio of 84%, but undetectable levels in the infant. The infant grew and developed normally.
Conclusion: The infant of a cyclosporine-treated mother was breast-fed exclusively during the first 10.5 months of life and did not absorb a detectable amount of the drug. Fetal growth and development were normal.