Excretion of morphine in human breast milk.

Five lactating women who underwent surgery and were treated with morphine epidurally or IV/IM in the postoperative phase were included in the study. The morphine concentrations in plasma and breast milk were determined 0, 15, 30, 45, 60, 90, 120, 240, 360 and 480 min after drug administration by means of a specific radioimmunoassay for morphine. The milk-to-plasma ratio was 2.45 +/- 0.8 (mean +/- s.d.). The amount of morphine transferred by nursing is, even at the peak concentration of 500 ng/ml milk, small and will hardly cause respiratory depression or drowsiness in the child.