The pill you are talking about is an emergency contraceptive pill which must be taken as early as accidental condom rupture, or missed oral combined pills or unsafe sex. However, it must not be taken as a routine medications after every unsafe sexual intercourse. If it is econ containing 1.5 mg of levonorgestrel, it can protect upto 72 hours,some say upto 120hours. The earlier, the better is what i say . About side effects, it has a wide range of side effects. Pregnancy in tubes (tubal), severe allergic reaction, nausea, vomiting, breast pain, menstural irregularities, headache, abdominal pain and so on are few side effects. please USE SAFE sexual PRACTICE AND AVOID CONSUMING REGULARLY ECON PILLS.