A new type of morning-after pill yet to be registered in Australia has been found to work for a longer period and be more effective at preventing pregnancies than the current drug available from pharmacies.
Reporting their findings today in the journal Lancet, researchers compared the widely used levonorgestrel, a Pharmacist Only medication in Australia, with ulipristal acetate, sold as a prescription drug in Europe only.
Women who took ulipristal acetate had a 1.8 per cent chance of becoming pregnant, compared with a 2.6 per cent chance in the levonorgestrel, the study's authors found.
After looking at nearly 1,700 women aged 16 to 36 who received emergency contraception within three days of having unprotected sex, researchers found there were 22 pregnancies in those who took levonorgestrel and 15 pregnancies in those who took ulipristal acetate.
Out of the 203 women who took emergency contraception between three and five days after sex, there were three pregnancies, and all three women took levonorgestrel.
While levonorgestrel interferes with ovulation in the early stages of the egg's development, ulipristal acetate, approved by the European Medicines Agency in May last year, delays ovulation until the egg is released from the ovary.
That difference may explain why ulipristal acetate works for two days longer than levonorgestrel, said study leader Professor Anna Glasier.
"This is still a new drug, and it has to be around for a couple of years without seeing any unexpected adverse events before anyone would contemplate making it available without prescription," she said.