Heather Boerner

February 16, 2017

SEATTLE — On-demand postexposure prophylaxis with doxycycline might significantly reduce the incidence of sexually transmitted infections (STIs), new research shows.

In fact, prophylaxis with doxycycline after sex resulted in a 47% drop in new infections, French researchers report.

These data are especially important now, said lead author Jean-Michel Molina, MD, from Hôpital Saint-Louis in Paris.

Rates of STI, especially syphilis and, increasingly, drug-resistant gonorrhea, have been rising dramatically among gay men for more than 6 years. Those infections increase susceptibility to HIV and can have devastating and permanent consequences on their own.

Dr Molina presented the study results during a late-breaker session here at the Conference on Retroviruses and Opportunistic Infections 2017.

"The findings are very, very important, and could have huge public health implications," said Wafaa El-Sadr, MD, from the Columbia University Mailman School of Public Health in New York City, who was not involved in the study.

"This intervention seemed to be highly effective. It also seemed pragmatic and easy to implement," she told Medscape Medical News.

This model of treatment — which combines pre-exposure prophylaxis (PrEP), post-exposure prophylaxis (PEP) for HIV, and antibacterial PEP for STIs — could become a new form of comprehensive sexual healthcare for gay men, Dr El-Sadr said.

Participants in the randomized open-label substudy conducted by Dr Molina and his colleagues — gay men from France and Canada at high risk for HIV — came from the Intervention Préventive de l'Exposition aux Risques avec et pour les Gays (IPERGAY) study. IPERGAY was designed to assess the efficacy and safety of sexual-activity-dependent PrEP with the combination of tenofovir plus emtricitabine.

The 116 men in the prophylaxis group were instructed to take two 100 mg doxycycline pills in the 72 hours after condomless sexual intercourse; the 116 men in the control group received no prophylaxis.

All the men received risk-reduction counseling and condoms, and all were tested every 8 weeks for HIV, syphilis, chlamydia, and gonorrhea.

At a median follow-up of 8.7 months, fewer men in the prophylaxis group than in the control group had acquired a bacterial STI (28 vs 45; hazard ratio, 0.53; 95% confidence interval, 0.33 - 0.85; P = .008).

Table. Reduction in Risk With Doxycycline Prophylaxis

Infection Reduction, % Hazard Ratio 95% Confidence Interval P Value
Gonorrhea 17 0.83 0.47–1.47 .52
Chlamydia 70 0.30 0.13–0.70 0.006
Syphilis 73 0.27 0.07–0.98 <.05


Overall, 71% of the men were asymptomatic.

Although the findings from this study raise hope, it is still too early to implement such treatment in the clinic, Dr Molina said.

"We don't yet have the results of the antibiotic-resistance study, and the long-term effect of this strategy is still unknown," he told Medscape Medical News. "At this point, antibiotic prophylaxis for STIs is still not recommended. We think more research is needed."

Resistance and Comprehensive Care

The issue of antibiotic overuse in American livestock, which can quickly diminish protection, was raised by some members of the audience.

Antibiotic resistance is among the chief concerns of Jeanne Marrazzo, MD, from the University of Alabama at Birmingham.

The idea of increasing resistance to drugs that have increasingly led to blindness and hearing loss in her patients with STIs "keeps me up at night," she said.

The take-home message from this substudy isn't that clinicians should start providing high-risk patients with doxycycline, it is the fact that 71% of STIs were asymptomatic, Dr Marrazzo told Medscape Medical News.

Doctors should never rule out syphilis, in particular, when they see a lesion on a gay man or a woman who could be pregnant, she said.

"They need to never assume that it's not syphilis, because it can take so many forms," Dr Marrazzo explained. "If someone has a genital lesion, do testing, maybe presumptively treat it. Do a careful neurologic history and exam; really probe for hearing loss, vision changes."

All of this, she said, needs to be done in the context of practices that affirm a person's "right to have a healthy sexual life."

"This is not just a social justice thing, it's also a health thing," she pointed out. "You do that by educating patients and giving them the tools to prevent STIs, and if they do get exposed, get them treated confidentially and appropriately. That means you have to invest in a system that makes that possible, which often means you need to have a public health system that picks up where the private health system might not be stepping up to the plate."

Dr Molina reports receiving funding from Gilead Sciences, ViiV Healthcare, and Merck. Dr El-Sadr and Dr Marrazzo have disclosed no relevant financial relationships.

Conference on Retroviruses and Opportunistic Infections (CROI) 2017: Abstract OA 91LB. Presented February 15, 2017.


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