Serum profile of isosorbide mononitrate after vaginal administration in the third trimester.

Vaginally administered nitric oxide donors such as isosorbide mononitrate have been used to ripen the uterine cervix in pregnancy. The pharmacokinetics of isosorbide mononitrate following vaginal administration are unknown. Serum levels of isosorbide mononitrate were determined at baseline and 60, 180 and 360 minutes after vaginal administration of 20 or 40 mg isosorbide mononitrate to pregnant women scheduled for induction of labour at term. Serum levels of isosorbide mononitrate continued to rise up to 360 minutes after isosorbide mononitrate insertion, with mean (SD) final levels of 337 (94) microg/L following isosorbide mononitrate 40 mg and 144 (47) microg/L following isosorbide mononitrate 20 mg, P < 0.01.