Hello, thanks for using HCM. Cytotec is a prostaglandin which causes ripening of the cervix and induces uterine contractions and or labour if given at the right dosage. However, the duration of onset depends on the method or route of admission and also on the dosage. One table of cytotec (200mcg) if properly inserted into the posterior fornix (inside the vaginal) is usually enough to induce contractions even in primigravidas (women with first pregnancy) while multigravidae will require as small as one quarter of a cytotec tablet vaginally to have contractions. Three tablets of cytotec taken at once orally has the same effect as a single tablet taken vaginally. The onset of contractions in the above two methods is usually after 4 hours. It would have been of great help if the volume of retained product was mentioned after the ultrasound because if small medical treatment with cytotec or ergotamine derivative (not used in some areas) would be okay. However, the next mangement will depend on your clinical presentation,if you are having per vaginal bleedings that are continuing despite the intake of the cytotec then another uterine evacuation will be required. For now, assumming therre is no bleeding or its not worrisome, lets just wait and see how it evolves. You need to be on antibiotics. Best regard and hope this helps.