Women seeking emergency contraception should tell their pharmacist if they are taking medicines to treat epilepsy, tuberculosis, HIV, or fungal infections – or are taking herbal remedies containing St John’s Wort – as these could reduce how well the pill works, the Medicines and Healthcare products Regulatory Agency (MHRA) said.

"To protect against unwanted pregnancies, women taking these medicines may need to take two packs of the emergency contraceptive in order for it to be effective," the watchdog said today (September 15).

The MHRA has produced a information sheet for pharmacists and prescribers to hand out to relevant patients, it said.

Dr Sarah Branch, deputy director of MHRA’s vigilance and risk management of medicines division, said this is "important new advice" for women who want to use the emergency contraceptive pill.

“Our new information sheet provides information on what types of medicines could interfere with how the emergency contraceptive works,” said Dr Branch. “It tells women what steps they need to take to ensure they receive the correct dose.”

Last week the Royal Pharmaceutical Society backed new guidance calling for healthcare professionals to alert women to the coil as an alternative to oral contraceptives. Read more here