Emergency contraceptive pills are effective when taken within 72 hours of intercourse. Emergency contraceptive pills are a temporary, emergency, one-time, post-contraceptive measure that usually has a higher success rate the sooner it is taken. The pill is effective within 72 hours of intercourse, and is ineffective beyond that time. It is important to note that the duration of the pill is based on the time of sexual intercourse. Emergency contraceptive pills are used to prevent pregnancy by inhibiting the implantation of a fertilized egg and by making the cervical mucus sticky, preventing sperm from penetrating, thus achieving contraception. However, this drug cannot be used for patients with breastfeeding, scanty menstruation, gynecological tumors, hepatitis and other major diseases. This drug should not be used after taking it to have unprotected sex again. After taking the drug, there is vomiting and other phenomena, you need to make up the dose in time. After taking the drug, some people have vaginal bleeding phenomenon, belonging to the withdrawal of bleeding, bleeding, etc. to go to the hospital obstetrics and gynecology consultation in time, timely stop bleeding and other treatments.