Hello, Thanks for your query. Primolut N tablets contain norethisterone, which is a synthetic hormone similar to the naturally occurring sex hormone progesterone. It is often used in endometriosis and is one of the primary treatments of endometriosis. The side effects include weight gain, loss of libido, depression, breast changes, irregular vaginal bleeding and breakthrough bleeding. Once Primolut is stopped, your periods appear in 2-3 days of stopping them but if you don’t get the periods within 7 days then you should report this to a gynecologist. Sometimes there is delayed menstrual cycle ( even for months) after taking this drug for a long time and in such a case it is important to consult a gynecologist and get the hormonal imbalance which may be caused by this drug, your pregnancy status and other causes of delayed periods ruled out. Hope this information helps you. I will be available to answer your follow up queries. Wishing you good health.