How often should you use emergency contraceptive

Dear Ask The Doctor: I had unprotected sex with a girl and bought her an emergency contraceptive the next day. Three days later we had a condom break. should we get another pill??

Dear Adam: Your partner can take the emergency contraceptive as many times as is needed, but it is important to note that repeated use of the emergency contraceptive pills may cause her menstrual cycle to change. She may experience a shorter or longer cycle and have a heavier or lighter period than normal. Emergency contraceptive pills should not be used as a substitute for regular contraception.  I hope the information helps, take care.