“A daily dose of a widely used antibiotic can prevent some infections with syphilis, gonorrhea and chlamydia, potentially a new solution to the escalating crisis of sexually transmitted infections, scientists reported on Thursday.
Their study was small and must be confirmed by more research. Scientists still have to resolve significant questions, including whether S.T.I.s might become resistant to the antibiotic and what effect it could have on healthy gut bacteria in people taking it every day. [..]
Previous studies have shown that the antibiotic doxycycline substantially cuts the risk of new infections if taken within 72 hours after unprotected sex. The C.D.C. now recommends taking doxycycline after “oral, vaginal or anal sex.”
The recommendation applies only to gay and bisexual men and transgender women who have had an S.T.I. within the previous year or who may be at risk for one. There is not enough evidence that the strategy, called doxy-PEP, works for other groups, the agency concluded.
The new study took a different tack, looking instead at preventing S.T.I.s with a daily dose of the drug, which may be better for individuals with frequent exposure to infections.
Some providers have suggested that patients might balk at taking antibiotics every day. But many patients told the researchers it would be easier for them to remember to take a daily dose along with a daily pill for H.I.V. prevention or treatment, said Dr. Troy Grennan, who heads the H.I.V. program at the BC Center for Disease Control in Vancouver and led the study. [..]
The researchers tested the men for S.T.I.s every three months and monitored microbial resistance to the antibiotic. They found that daily doxycycline slashed the rate of syphilis infections by 79 percent, chlamydia by 92 percent and gonorrhea by 68 percent.
The team has since found similar results in gay and bisexual men and trans women who do not have H.I.V.
Dr. Grennan said he was surprised to see that the strategy worked so well against gonorrhea, because about 60 percent of cases in Canada are resistant to tetracyclines, a class of antibiotics that includes doxycycline.
Dr. Grennan and his colleagues aim to recruit 560 men and trans women with and without H.I.V. to compare whether doxycycline taken every day is as effective as the antibiotic taken only as needed after sex.
Another study at the conference suggested that patients who take pills to prevent H.I.V. infection were not more likely to get S.T.I.s if they were screened twice a year instead of four times a year, as is currently recommended.
The reduced frequency may be more palatable and practical for patients, and may increase adherence to H.I.V. preventives, the researchers said.
The study, in the Netherlands, followed 448 gay and bisexual men in Amsterdam, Rotterdam, The Hague and Nijmegen who were taking H.I.V. preventive pills over 18 months. About half were scheduled to be screened for S.T.I.s every three months and the other half every six months.
Some participants in the six-month group sought out S.T.I. testing between the planned clinic visits. Even so, their overall visits were fewer than for those in the three-month group. Yet the rate of infections in the six-month group was only slightly higher. [..]
More frequent screening also may lead to overtreatment, especially of asymptomatic cases of chlamydia and gonorrhea that may clear on their own, Dr. [infectious disease physician at the University of Southern California Jeffrey] Klausner noted.
Publicly funded sexual health clinics in the United States are overwhelmed and don’t have enough staff or time to diagnose and treat more urgent cases of S.T.I.s, including syphilis in pregnant women, let alone asymptomatic cases, he said.
While asymptomatic infections may cause lasting harm to patients, including infertility, there’s no evidence that frequent screening and treatment for chlamydia and gonorrhea decreases rates in the population at large, Dr. Klausner said.”
Full article, A Mandavilli, New York Times, 2024.7.18