Hi, Welcome to HCM! Thanks for posting your query. I am happy to address your questions. Duvadilan retard is the brand name of a medicine called isoxsuprine and is a smooth muscle relaxer and is used to prevent premature labor. It has many actions on many organs, also it relaxes the muscles of the uterus. In the past this medicine was used to stop pre-term delivery. Pregnant women who take isoxsuprine have suffered from ileus (slow movement of intestine resulting in constipation, bloating and pain) which is the side effect of this drug but as you had spotting hence your clinician would have advised the same. Hope I have answered your query. If you have any further questions, I will be happy to help. Thanks