Is using antibiotics before exposure to STIs risky?

December 9, 2022 – Using antibiotics to prevent – not just treat – sexually transmitted infections was a fringe idea just a decade ago. Now it has the backing of several studies and the green light from a California public health department.

Jeffrey Klausner, MD, infectious disease physician and professor of public health at the University of Southern California, published the first randomized controlled trial on whether doxycycline — an antibiotic commonly used to treat infections including syphilis, chlamydia and others — could prevent STIs in 2015. At first, he says the National Institutes of Health didn’t want not fund the work, expressing concerns about the potential for antimicrobial resistance.

In the worst case, the microbes change over time and no longer respond to the drugs, and the treatments stop working.

But a growing STI crisis is forcing medical professionals to seek new options to help them.

“There were more than 170,000 cases of syphilis [in the U.S.] last year, and annual cases have doubled over the past five years,” says Klausner.

Repeated studies, with slightly different designs, also found lower rates of STIs in people who took doxycycline daily or after sex. The method, known as doxycycline pre-exposure prophylaxis, now has its own name: doxyPEP.

And in October, the San Francisco Department of Public Health doxyPEP recommended for cisgender men and transgender women who have had a bacterial STI in the past year as well as oral or anal sex without a condom with one or more cis men or trans women in the past year.

For those who meet the second criterion but have not been diagnosed with an STI in the past year, the department advises a “shared decision-making approach,” where doctors discuss the benefits and risks of the doxyPEP and prescribe it to patients who feel they will benefit from it, says Stephanie Cohen, MD, acting director of disease prevention and control in the Division of Population Health.

The department also recommends doxyPEP for anyone diagnosed with syphilis, regardless of gender or sexual partners.

Cohen says the United States has one of the highest rates of STIs in the world and that “San Francisco, in particular, has some of the highest rates of sexually transmitted infections in the country.”

Latest results

most recent study from doxyPEP followed 501 trans men and women in Seattle and San Francisco. About two-thirds were taking HIV pre-exposure prophylaxis (HIV PrEP) and the remainder were living with HIV. The results of this study, shared at the International AIDS Society (IAS) Conference earlier this year found that STIs were lower in the group asked to take a single dose of doxycycline within 72 hours of unprotected sex. The STI reduction rate was 66% in the HIV PrEP group and 62% in the HIV-positive group.

“It can be a bit of a paradigm shift when you’re talking about using antibiotics before someone has an infection,” says Annie Luetkemeyer, MD, an infectious disease physician and STI researcher at the University of California at San Francisco, who co-led the study.

She recalls that when HIV PreP came out, there was reluctance to think it would lead to riskier sex or increased resistance to HIV drugs. In fact, “we have learned that for some segments of the population, access to HIV PrEP has been absolutely critical to reducing HIV risk.”

Now the setback to doxyPEP is that it could lead to more antimicrobial resistance. But Luetkemeyer points out that the most-at-risk populations, for whom the intervention is aimed, are already exposed to high rates of antibiotic use, largely to treat STIs.

In the study’s control group, the STI rate was 32% over a 3-month period, compared to 11% in the doxyPEP group. But the use of doxyPEP wasn’t perfect, and study participants said they took it after 87% of unprotected sex, on average.

“It’s not about taking doxycycline versus not taking antibiotics,” says Luetkemeyer. In fact, the control group had a 50% higher exposure to ceftriaxone, a broad-spectrum antibiotic that has a higher potential, compared to doxycycline, to stimulate drug-resistant gonorrhea.

Still, Luetkemeyer and Klausner say it’s important to monitor both drug-resistant STIs, as well as other infections, such as those resistant to doxycycline. Staphylococcus aureusto ensure that doxyPEP does not increase them.

Make things worse?

Luetkemeyer and his colleagues are now studying to see if doxyPEP increases drug-resistant bacteria in those who take it. There are no red flags yet, but the search is ongoing.

While the San Francisco Department of Public Health gave the first official approval for doxyPEP, doctors who work with high-risk populations have been prescribing it off-label for years. Klausner says that when treating patients with HIV or at risk of contracting HIV, he would prescribe prophylactic doxycycline daily or after sex without a condom, depending on how frequently the patient had sexual activity. For use as needed, it would typically start with 15 doses at 200 milligrams, with refills.

He also notes that there is no fixed group of people who need doxyPEP, pointing out that people can benefit from it during a period between monogamous or relatively monogamous relationships, for example.

“People’s risk profile is dynamic. … doxyPEP is not a strategy that we encourage people to adopt forever,” he says.

And while doxyPEP could increase the risk of drug-resistant infections, it could also theoretically reduce it, reducing the burden of STIs in the population and the need for antibiotic treatments, Klausner says.

“It’s been known since the 1970s that sexually transmitted infections – like chlamydia, gonorrhea, syphilis – are perpetuated by a core group,” he says, typically men who have sex with many male partners for a period of time. month. “If you can control this spread of infection in the core group, the rest of the population is better protected.”

Cohen, of the San Francisco Department of Public Health, said “it’s definitely a priority as we deploy it to do surveillance to see if there are any concerning signs of antimicrobial resistance.” moment, “the community’s desire for new tools to protect against STIs outweighs the potential and unknown risks of antimicrobial resistance.”

What is certain is that decades of experience show that the only other prevention tool, condoms, will not be widely adopted by everyone, due to personal or partner preference.

“For some populations, with skyrocketing rates of sexually transmitted infections, what we currently have to offer is not working, so we really need new tools,” says Luetkemeyer.

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