Any drug taken orally will work for a certain period of time and will reach its effective concentration within a certain period of time to play a therapeutic or preventive role. The emergency contraceptive pill must be taken orally within 72 hours after intercourse in order to have the appropriate contraceptive effect. Therefore, if you want to use the emergency contraceptive pill, you must take it orally within 72 hours after intercourse. Even if the emergency contraceptive pill is taken orally within 72 hours after intercourse according to the instructions, it does not necessarily achieve 100% contraceptive effect, and its contraceptive rate is about 98%. Because 2% of patients have different individual differences or different sensitivity to the drug, it can also lead to contraceptive failure in clinical practice, so the oral emergency contraceptive pill should be taken orally within 72 hours after intercourse.