Duphaston is the brand name for Dydrogesterone, a progestin (a synthetic chemical which mimics progesterone, needed to maintain the menstrual cycle and sexual urges).
Duphaston was withdrawn from the UK market in 2008, as its use to maintain early pregnancy came under serious dispute. The drug is widely available elsewhere, however.
Common Side Effects of Duphaston
These include bleeding between menstrual periods, breast pain or tenderness, weight gain/loss, flatulence, headaches, leg cramps, migraine (seek immediate medical advice if you get a migraine for the first time while taking this drug), nausea, pelvic/stomach pain, weakness.
There are also certain other types of medicines and drugs that you should not take while you are on a course of Duphaston; your physician will be able to guide you on this matter. It is not advisable to take St John's Wort while taking Duphaston.
Taking Duphaston is linked with fertility issues, discussed here by a clinical laboratory director: