Emergency contraceptive pills are effective if taken within 72 hours of unprotected sexual intercourse. These pills are most effective when taken immediately after unprotected intercourse. Efficacy declines as time elapses between sex and drug administration. But it is reasonably effective for up to 120 hours and perhaps longer. However, you should remember that it is more effective the sooner it is taken after unprotected sex. However, it is not 100% effective, and pregnancy is possible even after its proper and timely use. You can take drospirenone ethinyl estradiol tablets for emergency contraception. Two pills within 72 hours of unprotected intercourse and next 2 pills after 12 hours. However the best emergency contraceptive pill is levonorgetrel 1.5 mg within 72 hours of unprotected sex. The common side effects of contraceptive pills include menstrual irregularities, nausea, vomiting, headache, dizziness, breast discomfort, depression, skin disorders, disturbance of appetite, weight changes, fluid retention, oedema, changes in libido, cholestatic jaundice, hair loss or hirsutism. These side effects are not permanent and usually resolve after stoppage of pills. Potentially fatal side effects are thrombocytopenia and stroke. These are very rare. Thanks