Excretion of indomethacin in breast milk.

1. The excretion of indomethacin into breast milk and subsequent exposure of infants was studied in 16 women and seven of their infants. The median milk:plasma ratio in seven patients where there were measurable drug concentrations in both milk and plasma was 0.37. 2. Total infant dose, assuming a daily milk intake of 150 ml kg-1 and 100% absorption, ranged from 0.07% to 0.98% (median = 0.18%) of the weight adjusted maternal dose. 3. Plasma samples were obtained in seven infants. In six of these, indomethacin concentrations were below the sensitivity of the assay (less than 20 micrograms l-1), while one infant had a plasma indomethacin concentration of 47 micrograms l-1. 4. No adverse effects due to indomethacin were reported in the infants.