A campaign to raise awareness about the effectiveness - or lack thereof - of the morning after pill in certain women is urgently needed, the Dublin Well Woman Centre (DWWC) has said.

It made its call following an admission by the manufacturer of one form of the emergency contraception that the medication may not work in heavier women.

The morning after pill can be taken up to 72 hours after having sex to prevent pregnancy. However, recent research has found that one type, 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).

The drug is currently being reviewed by the Irish Medicines Board (IMB).

Emergency contraception has been available over the counter in Irish pharmacies since 2011. Prior to this, a prescription was required.

According to DWWC chief executive, Alison Begas, making the medication available over the counter has been a ‘positive development for women', as they can now access it more easily, especially at peak times of demand, such as the weekends.

By seeking emergency contraception, these women are being ‘personally and socially responsible in seeking to avoid an unplanned pregnancy', she noted.

"However, there is also an important connection between accessing emergency contraception, and accessing holistic sexual healthcare, and this can only be delivered by a family planning clinic or GP.

"Emergency contraception is a very safe form of medication, but it is not a substitute for being on a more long-term form of contraception, and there's also a huge need to raise awareness around sexual health and sexually transmitted infections (STIs)," Ms Begas insisted.

Also commenting on this issue, DWWC medical director, Dr Shirley McQuade, said that it is important that women ‘know all of their options' when it comes to emergency contraception.

For example, there is now a five-day emergency contraception pill, called ellaOne, which is as effective on day five as it is on day one. However, this is only available with a prescription and is more expensive that the traditional morning after pill.

"There is also a five-day post-coital coil, which is the most effective form of emergency contraception, and this is fitted by a family planning doctor or appropriately qualified GP, up to five days after unprotected sex," Dr McQuade explained.

The CWWC said that in its clinical experience, many women are simply not aware of these five-day options. It also said that while the IMB's review of Norlevo is to be welcomed, ‘the knowledge gap over the impact of weight on efficacy of medication is worrying'.

It is calling for a major awareness campaign to highlight these issues.