Are emergency contraceptive pills affected by other medicines?

Some medications can make emergency contraceptive pills less effective at preventing pregnancy. This includes medicines used to treat epilepsy, HIV and tuberculosis (TB), other antibiotics and the herbal remedy St John’s Wort.

If you're taking any of these:

• you cannot use ellaOne or another pill containing ulipristal acetate (UPA). It might not be effective

• you can use Levonelle or any levonorgestrel (LNG) emergency contraception, but you might need to take a higher dose. Our clinical team can help you work out what you need

Ulipristal acetate (UPA) pills like ellaOne may not be suitable if you're using proton pump inhibitors such as omeprazole (antacids that regulate stomach acid levels). Read the information that comes with your medicine and get in touch if you have any questions or concerns.