Evaluating misoprostol content in pregnant women with hourly oral administration during labor induction by microElution solid phase extraction combined with liquid chromatography tandem mass spectrometry

Determination of misoprostol acid in plasma samples by UPLC-MS/MS with application in a maternal-fetal pharmacokinetic study following a low misoprostol dose vaginally to induce labor

Misoprostol is a prostaglandin E1 synthetic analogous used for elective interruptions of early pregnancy, treatment of incomplete abortion, postpartum hemorrhage and induction of full-term labor. Its a lipophilic drug, passing by extensive and rapid pre-systemic metabolism into the active metabolite, misoprostol acid (MA). The objective of this study was to develop and validate a highly sensitive method for MA determination in plasma using UPLC-MSMS, with application in a study of maternal-fetal pharmacokinetics in healthy parturients women (n = 10) after administration of 25 μg misoprostol vaginally. The method presented linearity of 2-10 pg/mL and acceptable precision, accuracy, plasma and solution stability. The parturients women presented median (interquartile range) values of AUC^0-6 of 68.0 (40.8-84.7) pg.h/mL, C_max of 21.9 (11.9-30.1) pg/mL and T_max of 2.25 (0.69-5.00) h. The placental transfer of MA was assessed from the umbilical vein/maternal blood ratios of 1.40 (0.91-2.13) and intervillous space/maternal blood ratios of 0.49 (0.15-3.41). In conclusion, this method presented high sensitivity, being able to quantify MA in plasma samples following a low 25 μg misoprostol administered vaginally aimed to induce labor in parturients women. Additionally, this is the first description of the placental transfer of MA after a vaginal administration of misoprostol.