Most women can use emergency contraceptive pills. This includes women who can't use hormonal contraception, such as the combined pill and contraceptive patch. Girls under 16 years old can also use it.

But you may not be able to take the emergency contraceptive pill if you're allergic to anything in it, have severe asthma or take any medicines that may interact with it, such as:

• the herbal medicine St John's Wort

• some medicines used to treat epilepsy, HIV, or tuberculosis (TB)

• medicine to make your stomach less acidic, such as omeprazole

• some less commonly used
  antibiotics (rifampicin and rifabutin)
   

  •      These pills are used to control unwanted  pregnancy when a couple does unprotected sex, they are taken within 72 hours of unprotected sex 
         

  • Levonorgestrel is a hormone that can be used for emergency contraception. Emergency contraception should not be used as a routine method of birth control.

  • Levonorgestrel can prevent pregnancy after unprotected sex. People sometimes call it the "morning-after pill." But you don't have to wait until the morning after sex to take it. In fact, levonorgestrel is more effective the sooner you take it. It is a one-dose regimen: you take one pill. The pill contains 1.5 milligrams of levonorgestrel, which is used in lower doses in many birth control pills.