The Irish Medicines Board (IMB) has said it is reviewing ‘available data' on the morning after pill, after it emerged that the medication may not work on overweight or obese women.

The morning after pill, also known as emergency contraception, can be taken up to 72 hours after having sex to prevent pregnancy. However, recent research has found that one type of morning after pill, Norlevo, which is available in Ireland, is less effective if taken by women over a certain weight.

From January 2014, the manufacturer of the drug, HRA Pharma, plans to update its product information, cautioning women that the medication is not effective in those who weigh over 176lbs (12 stone, 8lbs). It will also state the medication may not be as effective in women who weigh over 165lbs (11 stone, 11lbs).

Concerns have now been raised that other emergency contraception pills may not work in women of a certain weight as well.

According to the IMB, together with its EU counterparts, it is ‘currently reviewing the available data on this issue to consider the need for updates to the product information and subsequent communication to healthcare professionals'.

"As with all medicines, the IMB continuously monitors their safety to ensure that an appropriate balance exists between the benefits of a particular medicine against the potential risks," the board added.