Levonelle contains levonorgestrel, a synthetic version of the natural hormone progesterone. In a woman’s body, progesterone plays a role in ovulation and preparing the uterus for accepting a fertilised egg.
It’s not known exactly how Levonelle works, but it’s thought to work primarily by preventing or delaying ovulation. It does not interfere with your regular method of contraception.
ellaOne contains ulipristal acetate, which stops progesterone working normally. It prevents pregnancy mainly by preventing or delaying ovulation.`
Levonelle and ellaOne do not continue to protect you against pregnancy. This means that if you have unprotected sex at any time after taking the emergency pill you can become pregnant.
Even if you're starting or continuing another method of hormonal contraception, it may not be effective immediately. You'll need to use condoms or avoid sex until the contraception is working effectively. Your doctor or nurse will tell you when you can start hormonal contraception and how long you'll need to take extra precautions to prevent pregnancy.
Levonelle and ellaOne are not intended to be used as a regular form of contraception. However, you can use emergency contraception more than once in a menstrual cycle if necessary.