Pharmacokinetics of a novel oral slow-release form of misoprostol

BACKGROUND: The pharmacokinetics of a novel slow-release (SR) misoprostol was studied and compared to conventional misoprostol. METHODS: Thirty-one women, pregnant between 8 and 12 weeks, requesting surgical abortion were randomly allocated to receive orally 400 microg conventional misoprostol, 400 microg SR misoprostol or 800 microg SR misoprostol. Venous blood samples were taken at 0, 30, 60, 120, 240 and 360 min after the administration of misoprostol. Misoprostol acid (MPA) was determined in serum samples using liquid chromatography/tandem mass spectrometry. RESULTS: Serum peak concentration (Cmax) was highest for conventional oral misoprostol. The time to peak concentration (Tmax) was similar for all groups. The area under the curve up to 360 min was similar for conventional and for 800 microg SR misoprostol and significantly greater for these groups compared to 400 microg SR misoprostol (P = 0.013). CONCLUSION: The new SR form of misoprostol demonstrated lower peak levels but longer-lasting elevation in plasma levels compared to conventional oral misoprostol. The AUC for 800 microg SR misoprostol was similar to that of 400 microg of conventional oral misoprostol. SR misoprostol may offer an alternative to repeated administration of oral misoprostol or to vaginal administration.