Cyclosporine and lactation: when the mother is willing to breastfeed.

We describe a woman treated with cyclosporine after renal transplantation who commenced breastfeeding of her newborn infant. The child had no apparent clinical adverse effects to cyclosporine. To confirm the safety of breastfeeding and guide the patient and her clinician, cyclosporine concentrations in maternal blood, breast milk, and infant blood were measured. Maternal cyclosporine concentration (1-hour postdose) was 49 μg/L, and the breast milk cyclosporine concentration (2-hour postdose) was 46 μg/L. Infant cyclosporine blood concentration shortly after breastfeeding was undetectable (<10 μg/L). Analysis revealed that the estimated infant exposure to cyclosporine via breast milk was minimal and provided reassurance to continue breastfeeding in this case.