Scientists have discovered a simple way to boost the effectiveness of a common emergency contraceptive pill

According to a recently published randomized controlled trial scalpelCombining the anti-inflammatory drug piroxicam, often prescribed for arthritis pain, with levonorgestrel emergency contraceptive pills after unprotected intercourse reduces pregnancies compared to taking levonorgestrel alone.

Two types of emergency contraception — containing either levonorgestrel or ulipristal acetate — are the most commonly used emergency contraception in most countries, with levonorgestrel available in more countries than ulipristal acetate. Both contraceptive methods work by preventing or delaying ovulation, and neither is effective after ovulation.

The accepted efficacy of levonorgestrel is based on the results of a 1998 trial in which levonorgestrel 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 hours. . -72 hours. However, more recent research suggests that the effectiveness of levonorgestrel may be lower.

“The emergency contraceptive pill containing levonorgestrel is one of the most popular options for emergency contraception in many parts of the world, so finding out that there is a widely available drug that increases the effectiveness of levonorgestrel when taken together is really exciting,” said Dr. Su Lu of the Hong Kong Planned Parenthood Association, a co-author of the study.

Study first author Dr Raymond Lee from the University of Hong Kong added: “Our study is the first to suggest that a safe, readily available drug taken concomitantly with levonorgestrel can prevent more pregnancies than levonorgestrel alone. We hope these findings will lead to further From research and ultimately changes in clinical guidelines to giving women around the world access to the most effective emergency contraception.

The study was conducted at a major community sexual and reproductive health service in Hong Kong between August 2018 and August 2022. Women who required emergency contraception with levonorgestrel within 72 hours of having unprotected sex were randomized to receive a single supervised dose of levonorgestrel 1.5 mg. In addition to either piroxicam. 40 mg or a placebo pill. Neither the participants nor the attending healthcare professionals knew which group received which treatment. A follow-up appointment was made 1 to 2 weeks after the next expected period. During the appointment, if the normal menstrual cycle does not occur at that time, a pregnancy test is performed. The proportion of pregnancies prevented from those expected was calculated based on a static model published in 1998.

Of the 836 women followed, there was one pregnancy among the 418 women taking piroxicam and levonorgestrel and seven pregnancies among the 418 women taking placebo and levonorgestrel. The expected pregnancies without contraception were estimated at 4.5% (19/418) in both groups. Therefore, the percentage of pregnancies prevented after combined treatment with piroxicam and levonorgestrel was 95% (18/19), compared to 63% (12/19) in those taking levonorgestrel and placebo.

There were no significant differences in the rates of side effects between those receiving piroxicam and the combined placebo treatment.

“Levonorgestrel prevents pregnancy by preventing or delaying the rise of luteinizing hormone, which disrupts ovulation,” explained Professor Kristina Gemsel-Danielsson of the Karolinska Institutet, another co-author. Piroxicam may work by targeting a different type of hormone – prostaglandins. Prostaglandins facilitate several reproductive processes including ovulation, fertilization, and embryo implantation. Therefore, we speculate that piroxicam may provide a contraceptive effect both pre-ovulatory (by preventing the ovulation process) and post-ovulatory (by preventing implantation of the embryo), however, our trial did not investigate the mechanism of action of piroxicam and did not perform further studies. Confirmation is required.”

The authors acknowledge some limitations of the study, including the possibility of generalization of the results to other settings. Because the study excluded women who were currently or had recently used hormonal contraception, as well as those who had more than one episode of unprotected sex before taking emergency contraception, it is not certain whether combined treatment with piroxicam and levonorgestrel would be equally effective when Apply it to women. women in those circumstances.

“Overall, this study suggests that anyone using levonorgestrel 1.5 mg as an emergency contraceptive pill should consider supplementing with 40 mg of piroxicam via route,” Dr. Erica Cahill of Stanford University School of Medicine, who was not involved in the study, said in an associated comment. Oral, because it improves efficacy with minimal side effects.These conclusions may not apply to all patients, as this study was restricted to a specific population, where most of the participants were of Asian ethnicity and weighed less than 70 kg.Because emergency contraception with levonorgestrel Less effective in obese subjects, the efficacy shown here may not be generalizable to patients with a higher BMI.

Reference: “Oral emergency contraception using levonorgestrel plus piroxicam: a randomized, double-blind, placebo-controlled trial” by Raymond Hang-won Lee, Su Sin Tsing Lu, Christina Gemsel-Danielson, Carol Ho-yi-fung, Pak Chung-ho, and Ernst Hong Yu Ng, 16 Aug. 2023, scalpel.
doi: 10.1016/S0140-6736(23)01240-0

This study was funded and conducted by researchers from the Department of Obstetrics and Gynecology at the University of Hong Kong.