Taking antibiotics within 72 hours of sexual exposure reduces sexually transmitted infections by two-thirds

A new study found that the antibiotic doxycycline prevented sexually transmitted infections (STIs) in men (MSM) and transgender women who had sex with medicated men within 72 hours of having unprotected sex. was shown.

Specifically, a post-exposure approach called doxy-PEP reduced the incidence of syphilis, gonorrhea and chlamydia in study participants by two-thirds, all of whom reported having contracted a sexually transmitted disease in the previous year. .

The results of this study are New England Journal of Medicine. It was funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

“This is a promising finding that could help reduce the number of sexually transmitted infections in the most at-risk populations,” said NIAID Acting Director Hugh Auchincloss, M.D., in a statement.

Prevention remains a key challenge, especially in the face of rising numbers of infected people. Over the past few years, the incidence of sexually transmitted diseases has increased in the United States, with a disproportionate impact among MSM and transgender women. An estimated 2.5 million cases of syphilis, gonorrhea and chlamydia will occur in her 2021, up from her 2.4 million in 2020, according to the CDC.

“There is a desperate need for effective methods to prevent sexually transmitted infections,” said Auchincloss.

Investigators conducted an open-label, randomized study of 501 participants using two cohorts. The first cohort included 327 participants, known as MSM and transgender women taking her PrEP for HIV infection (PrEP cohort), and another cohort included 327 participants with HIV infection. 173 participants living with HIV (those living with HIV) were included. [PLWH) cohort) and who had had gonorrhea, chlamydia, or syphilis in the past year.

Participants were randomly assigned in a 2:1 ratio to take 200 mg of doxycycline within 72 hours after condomless sex (doxycycline postexposure prophylaxis) or receive standard care without doxycycline. STI testing was performed quarterly. The primary end point was the incidence of at least one STI per follow-up quarter.

“In the PrEP cohort, an STI was diagnosed in 61 of 570 quarterly visits (10.7%) in the doxycycline group and 82 of 257 quarterly visits (31.9%) in the standard-care group, for an absolute difference of −21.2 percentage points and a relative risk of 0.34 (95% confidence interval [CI]0.24 to 0.46; P<0.001),” the researchers wrote.

It’s important to note that the results of this study also revealed a modest increase in antimicrobial resistance.

“Of the participants with available gonorrhea cultures, 5 of 13 in the doxycycline group and 2 of 16 in the standard-of-care group developed tetracycline-resistant gonorrhea,” the authors wrote.

The researchers suggest that this may be why doxy-PEP is less protective against gonorrhea strains that are already tetracycline-resistant, suggesting that broader population-based surveillance for this type of resistance is important. says there is.

Additionally, researchers found that doxy-PEP decreased. Staphylococcus aureus— “colonization” of bacteria commonly found on skin — reduced by 50% after one year.but in those who still had Staphylococcus aureus A slightly higher proportion of the doxy-PEP group showed doxycycline resistance (16% vs. 8%).This is important because doxycycline may be used to treat methicillin resistance Staphylococcus aureus Skin and soft tissue infections.

The researchers noted that a longer follow-up period is needed to examine the potential antimicrobial resistance effects of intermittent doxy-PEP use. The use of Doxy-PEP in other populations disproportionately affected by sexually transmitted infections, such as women with dysbiosis, also deserves clinical study.