A morning after pill is more effective at preventing pregnancies when taken with an anti-inflammatory medication, a new study has suggested.
Taking piroxicam, a drug commonly used for arthritis pain, at the same time as the levonorgestrel emergency contraceptive pill after unprotected sex prevents significantly more pregnancies compared to taking levonorgestrel alone, researchers found.
According to the study, 95% of pregnancies were prevented after combined treatment with the drugs, compared to 63% of pregnancies being prevented when levonorgestrel was taken alone.
The researchers say that if their findings can be reproduced in the future, clinical guidelines should change to offer both piroxicam and levonorgestrel when levonorgestrel is the emergency contraception of choice.
Dr Sue Lo, from the Family Planning Association of Hong Kong, a co-investigator of the study, said: “The levonorgestrel emergency contraceptive pill is one of the most popular choices of emergency contraception in many parts of the world, so finding out that there is a widely available medication which increases levonorgestrel’s efficacy when they are taken together is really exciting.”
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 Raymond Li, University of Hong Kong
First author of the study 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.”
Two types of emergency contraceptive pills – containing either levonorgestrel or ulipristal acetate – are the most widely used emergency contraception method in most countries.
Both of them work by preventing or delaying ovulation and neither are effective post-ovulation.
According to the researchers, the accepted effectiveness of levonorgestrel is based on the results of a trial from 1998 in which it prevented 95% of expected pregnancies when taken within 24 hours of unprotected sex, 85% if taken within 25–48 hours, and 58% if taken within 49–72 hours.
However, more recent research suggests the effectiveness of levonorgestrel might be lower.
The new study took place at a major community sexual and reproductive health service in Hong Kong between August 2018 and August 2022.
Women who required levonorgestrel emergency contraception within 72 hours of unprotected sex were randomly assigned to receive a single supervised dose of levonorgestrel 1.5 mg plus either piroxicam 40 mg or a placebo pill.
A follow-up appointment was scheduled one to two weeks after the next expected period and if a normal period had not occurred by that time, a pregnancy test was carried out.
Researchers calculated the proportion of pregnancies prevented out of those expected using an established model published in 1998.
Of the 836 women followed up, there was one pregnancy among the 418 women who took piroxicam and levonorgestrel and seven pregnancies among the 418 women who had the placebo and levonorgestrel.
The percentage of expected pregnancies without contraception was estimated at 4.5% (19/418) in both groups, the study published in The Lancet found.
Therefore, the percentage of pregnancies prevented following piroxicam-levonorgestrel co-treatment was 95% (18/19), compared with 63% (12/19) in those who took levonorgestrel and placebo.
Women with current or recent use of hormonal contraception were excluded from the study, as well as those with more than one episode of unprotected sex before taking emergency contraception.
Dr Janet Barter, president of the Faculty of Sexual and Reproductive Healthcare, said: “We welcome the findings of this new study which has the potential to improve the efficacy of emergency contraception, which is very exciting.”
She added there are currently three forms of emergency contraception available in the UK – oral levonorgestrel (LNG), oral ulipristal acetate (UPA) and the emergency copper intrauterine device (IUD), which is the most effective.
Dr Janet Nooney, expert scientific assessor in the MHRA benefit risk management unit, said: “This study raises an interesting possible improvement in emergency contraceptive effect when levonorgestrel is used in combination with piroxicam tablets (a non-steroidal anti-inflammatory drug [NSAID]).
“Importantly, in the UK oral piroxicam tablets are no longer recommended for acute pain relief or inflammatory conditions as it is associated with serious gastro-intestinal side effects and rare but possibly fatal skin reactions.
“These side effects may limit its suitability for wider use in combination with emergency contraception.
“Further work would be needed to see if similar effects on emergency contraception are seen in a wider population (including younger women with higher body weights) than was studied in the trial and with an alternative NSAID that is authorised for use in a broader population.”
