Chlamydia, gonorrhea and syphilis are on the rise in Canada, but a growing number of research shows that taking a particular antibiotic drug after sex may help prevent sexually transmitted infections (STIs).
The antibiotic drug doxycycline has been on the market for more than 50 years and has been typically used to treat skin infections; however, experts say it can also be used as a ‘morning-after pill’ to prevent STIs.
Some physicians are starting to prescribe the antibiotic to patients as a preventative tool against STIs, according to Dr. Troy Grennan, physician lead for the Provincial HIV/STI Program at the BC Centre for Disease Control.
“I have patients taking it as an intervention and several colleagues who have patients on this,” he said. “And these are patients who really do qualify for this; they’ve perhaps struggled with several infections over the course of a year and are really looking to be proactive in their health.”
When a doctor in Canada does prescribe doxycycline as a prevention tool for STIs, Grennan said it will be used off-label, as it is not an approved Health Canada approved indication.
The efficacy of doxycycline as a prevention tool for STIs has been researched since 2015, he said, and there have been several studies since then showing the drug’s success.
The latest study, published on April 6 in the New England Journal of Medicine, showed the drug’s potential to prevent STIs among men who have sex with men and transgender women.
“Doxycycline made the most sense for several reasons. One, it’s inexpensive and has a long safety profile,” explained Connie Celum, a professor of global health and medicine at the University of Washington and study author.
“Biologically, it has activity against chlamydia, gonorrhea and syphilis, and therefore it made sense since those are the three most common bacterial STIs. Doxycycline was really one of the only antibiotics that would have activity against all three sexually transmitted infections.”
In the study, about 500 gay or bisexual men and transgender women in Seattle and San Francisco with previous STD infections took one doxycycline pill within 72 hours of unprotected sex.
Those who took the pills were about 90 per cent less likely to get chlamydia, about 80 per cent less likely to get syphilis, and more than 50 per cent less likely to get gonorrhea compared with people who did not take the pills after sex, the researchers found.
Grennan called this study a “game-changer” and hopes more public health officials, including Health Canada, will take notice.
A spokesperson for Health Canada told Global News in an email that doxycycline is approved in Canada, but the medicine’s approval list does not include STI prevention.
The San Francisco Department of Public Health in October became the first U.S. health department to issue guidance about doxycycline as an infection-prevention measure.
And the U.S. Centers for Disease Control and Prevention (CDC) is drafting recommendations for using it as a kind of morning-after pill for preventing STDs, Dr. Leandro Mena, director of the agency’s STD prevention division, told the Associated Press.
Canada's rising STI rates
Canada’s STI rate has been on the rise for more than a decade.
Between 2011 and 2019, rates of chlamydia increased by 26 per cent, gonorrhea shot up 171 per cent and infectious syphilis, jumped to 389 per cent, according to the Public Health Agency of Canada (PHAC).
The rates have gone up since 2019 in many provinces as well.
For example, STI rates increased in Alberta between 2020 and 2021, according to Alberta Health. Gonorrhea rates increased 2.4 per cent, HIV went up 25.4 per cent and infectious syphilis climbed 27.6 per cent.
In Manitoba, between April 2021 and April 2022, chlamydia cases went up to 1,800 from 1,570, gonorrhea rose to 761 cases from 557 cases, HIV went up to 63 from 37, and congenital syphilis nearly doubled to 14 cases from eight.
Greenan believes there are a number of reasons leading to the spike in infections.
STI testing in Canada has gone up over the years, he explained, meaning infections are more likely to be detected.
“The other things that we feel might be playing a role are changes in behaviours; maybe people are having more sex and maybe people are using condoms less often,” he said.
Given the dramatic increases in STIs, Greenan said conventional strategies, such as awareness campaigns and promoting condom use, are not working well enough.
“That really called for the need to rethink how we do this,” he said, adding that started a movement for researchers to turn to the antibiotic doxycycline.
Both Greenan and Celum agree that more studies need to be conducted in order for the antibiotic to be more accepted in public health.
Greenan and his team of researchers have already completed one study on the topic, which has been submitted for publication. And he is currently about to launch a new randomized controlled trial involving examining the use of doxycycline for bacterial STI prevention across Canada, he said.
What about antibiotic resistance?
The researchers of the study published in the New England Journal of Medicine acknowledged the potential for antibiotic resistance.
When antibiotics are used too frequently or incorrectly, they can contribute to the development of antibiotic-resistant bacteria, which is when bacteria evolve to become resistant to the effects of antibiotics.
To tackle this concern, Celum said the researchers are planning on doing studies in multiple cities in the U.S. in order to further examine the benefits and drawbacks of the drug against STIs.
“I think that’s a very legitimate concern. We saw very little evidence of that in our clinical trial and the other two trials that have been done in men,” she said.
“We’ll continue to try to study whether or not there’s an impact on antimicrobial resistance and try to look at the net benefit as well as potential risks and terms of resistance.”