Postinor 2 is mostly used as an emergency birth control pill. Normally it should be used within the 72 hours you had an unprotected sexual intercourse. it is about 95% effective but the longer the time it takes to use it, the less effective it becomes.

Possible Side effects of Postinor 2 you should know are nausea, Abdominal pain
fatigue, headache, menstrual changes, dizziness, breast tenderness or vomiting

But note that you can't take Postinor 2 if you're are pregnant. If you previously had unprotected intercourse more than 72 hours earlier in the same menstrual cycle, as you may already be pregnant or you're are experiencing vaginal bleeding for which the reason is not known, you can't take Postinor 2