The morning after pill works better when taken alongside a drug usually given to patients with arthritis, researchers have found.
Levonorgestrel, sold as Levonelle in Britain or Plan B in the US, was found to be 63 per cent effective on its own.
This jumped to 95 per cent when given with piroxicam, an anti-inflammatory drug that costs around 30p a tablet.
Experts said their findings, published in the prestigious medical journal The Lancet, were ‘exciting’.
Doctors should now consider prescribing piroxicam to women seeking emergency contraception, the University of Hong Kong team claimed.
Levonorgestrel, available as Levonelle in Britain, was found to be 63 per cent effective on its own. This jumped to 95 per cent when given with piroxicam, a prescription-only anti-inflammatory drug
Their trial involved 836 women who sought the morning after pill within 72 hours of having unprotected sex.
Volunteers were randomly split into two groups during the four-year study.
Half were given levonorgestrel — a synthetic version of progesterone, which delays the release of the egg — with a placebo. Others got the morning after pill alongside 40mg of piroxicam
Follow-up appointments were arranged for after their next expected period. If it had not occurred, they took a pregnancy test.
Only one pregnancy occurred among the 418 women in the piroxicam group. Seven happened among women given the placebo.
Researchers estimated that around 4.5 per cent — or 19 of the 418 women — would get pregnant without emergency contraception.
Therefore, they concluded that piroxicam taken with levonorgestrel prevented 18 of the 19 pregnancies (95 per cent), compared to 12 out of 19 with the pill alone (63 per cent).
No major side effects were noted.
Study co-author Professor Kristina Gemzell-Danielsson, from the Karolinska Institute in Sweden, said: ‘Levonorgestrel prevents pregnancy by blocking or postponing the luteinising hormone surge, which disrupts the ovulatory process.
‘Piroxicam might work by targeting a different type of hormone – prostaglandins.
‘Prostaglandins facilitate several reproductive processes including ovulation, fertilisation, and embryo implantation.
‘Therefore, we speculate that piroxicam may provide a contraceptive effect both pre-ovulation — by blocking the ovulatory process — and post-ovulation — by preventing the implantation of the embryo.’
Emergency contraception, which also includes the IUD coil, can be taken up to five days after sex to avoid unwanted pregnancy.
It works by preventing ovulation or altering the lining of the womb to stop an egg becoming implanted, avoiding a pregnancy.
In the UK, the morning-after pill is offered for free on the NHS at GP surgeries, sexual health clinics and walk-in centres across the UK.
But this option is not available on weekends and women are usually questioned by a healthcare professional before receiving the tablet.
Emergency contraception can also be bought from pharmacies after a consultation.
Academics behind the new study, however, warned there were potential limitations.
These included excluding women who were currently or had recently used hormonal contraception, as well as those who had had unprotected sex more than once before taking emergency contraception.
Studies also show the morning after pill can fail when taken by overweight women.
Responding to the study’s findings, Dr Erica Cahill, from Stanford University School of Medicine, said: ‘These conclusions might not apply to all patients.
‘This study was limited by a specific population, with participants being mostly of Asian ethnicity and weighing less than 70kg.
‘Given that levonorgestrel emergency contraception is less effective in people with obesity, the efficacy shown here might not be generalisable to patients with higher BMIs.’
But Dr Sue Lo, of the Family Planning Association of Hong Kong and co-investigator of the study, said the findings were ‘really exciting’.
Doctors should now consider prescribing piroxicam to women seeking emergency contraception, the University of Hong Kong research team claimed
She added: ‘The levonorgestrel emergency contraceptive pill is one of the most popular choices of emergency contraception in many parts of the world.
‘So finding out there is a widely available medication which increases levonorgestrel’s efficacy when they are taken together is really exciting.’
Meanwhile, study author Dr Raymond Li from The University of Hong Kong, said: ‘Our study is the first to suggest that a readily available and safe medication taken at the same time as the levonorgestrel pill can prevent more pregnancies than levonorgestrel alone.
‘We hope these results will lead to further research and ultimately changes in clinical guidelines to enable women around the world to access more effective emergency contraception.’
Dr Cahill added: ‘Overall, this study suggests anyone administering levonorgestrel as emergency contraceptive pills should consider the addition of 40mg piroxicam orally, as it improves efficacy with minor side effects.’
The research comes almost a year after a group of MPs backed calls for the NHS to provide a same-day delivery service for the morning-after pill in the UK.
It followed a Deliveroo-style pilot with students during freshers week in Manchester.
The trial, which was the first of its kind in the UK, delivered emergency contraception to women using a bike courier hours after they completed a short questionnaire online.
Read More: World News | Entertainment News | Celeb News
