The purpose of this study to compare breast milk pharmacokinetics between miso prostol 200 μg and methylergometrine 250 μg after single oral dosing in women who require postpartum uterotonic therapy. Open prospective randomized phase I s tudy measuring misoprostol and methylergometrine on postpartum days 3 to 6 in mi lk 0.5, 1, 2, 3, 4, and 5 hours postdose, and in maternal serum at 0.5 and 1 hou rs (misoprostol) and 1 and 2 hours (methylergometrine) in 10 lactating women per group. Milk misoprostol levels rose and declined rapidly, which gave a milk eli mination half-life of less than one half that of methylergometrine (mean ±SE,1 .1 ±0.3 hours [median, 0.6 hours] vs 2.33 ±.0.3 hours [median, 1.9 hours]; P = . 003)-. Milk/plasma ratios for misoprostol were one third of those for methyle rgometrine at 1 hour (P <. 0001) and 2 hours (P <. 0015). Misoprostol warrants f urther investigation as an alternative to postpartum methylergometrine because i t enters and leaves breast milk at twice the rate, with one third of the milk/pl asma ratio, which significantly lowers infant exposure and facilitates a timed d osing regimen.
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