Medical Minute: STI Prevention

Doctors should weigh prescribing some of their patients a pill of a powerful antibiotic, doxycycline, to prevent the spread of sexually transmitted infections, according to new draft recommendations released Monday by the Centers for Disease Control and Prevention.

Officials say the approach, dubbed doxycycline post-exposure prophylaxis, or Doxy-PEP for short, could mark a turning point in the nation's fight against the ongoing epidemic of sexually transmitted infections, or STIs.

It comes after growing early research has found that doxycycline could prevent bacterial infections from taking root when taken in the days soon after potential exposure during sex, instead of reserving pills of the antibiotic only for doctors treating diseases after they are diagnosed. 

"It's going to take game-changing innovations for us to turn the STI epidemic around. And Doxy-PEP is the first major new prevention intervention we have for STIs in decades," Dr. Jonathan Mermin, head of the CDC's National Center for HIV, Viral Hepatitis, STD, and TB Prevention, said in an interview. 

Mermin, who co-authored the draft, estimated that implementation of their Doxy-PEP recommendations could lead to tens of thousands of infections prevented.

The recommendations will remain open for comments for 45 days. After incorporating that feedback, Mermin said he expects a final version to be published in the first quarter of next year. 

"We think this is the right step right now, even though science is still evolving," he said.

Who should take Doxy-PEP?

For now, the CDC's draft recommendations for offering the antibiotic are limited to the groups of Americans hardest hit by the STI epidemic: gay, bisexual and other men who have sex with men, as well as transgender women.

Among those communities, the CDC further narrowed the scope of its recommendation to those who have been diagnosed in the past year with at least one STI caused by bacteria, such as gonorrhea, chlamydia or syphilis. Others could be considered based on participating in events that raise the risk of exposure to STIs.

For people who the agency estimates "would benefit the most" from Doxy-PEP, the agency will tell doctors that prescribing a 200 mg dose of doxycycline "should be considered" for patients to take as soon as possible — no more than 72 hours — after oral, vaginal or anal sex.

What's known about how the antibiotic works suggests that Doxy-PEP "should be effective in other populations" as well, the agency acknowledges. However, the CDC stopped short of making a firm recommendation for or against offering it to a broader range of Americans.

A randomized trial in cisgender women had failed to show a benefit, though follow-ups suggested the results may have been muddied by many participants not actually taking the antibiotic. More data is needed before deciding on broad recommendations, officials concluded.

"The decision could still be made to take Doxy-PEP to prevent STIs. If that's done, we do recommend that they follow the same recommendations and processes that we put into place for others. So we're not saying don't do it," said Mermin.

How long will it take to roll out Doxy-PEP?

The CDC's draft comes as a growing number of health departments and sexual health clinics have already moved to start offering Doxy-PEP on their own.

"There is not a lot of money in STI care, prevention and research. So this development is profound for our field. And the community has already been working hard to implement Doxy-PEP and clinicians in some public health clinics are prescribing this widely," said David Harvey, executive director of the National Coalition of STD Directors.

Harvey's group lists 10 agencies and organizations that have already published policies and guidance on Doxy-PEP, including state health departments in California, Michigan and New Mexico.

Many more are still "desperately eager" for CDC to officially weigh in, Harvey said, and could begin offering prescriptions quickly once the guidelines are made official. An official recommendation from the CDC could also clear the way for ensuring coverage of the costs of the pills through public health budgets and insurance companies, he said.

"The good news about doxycycline though is that it is a fairly cheap drug. It's a drug that's been around for a long time. So this is unlike what we see with some HIV medications that are very, very expensive," Harvey said.

What are the risks of Doxy-PEP?

Harvey cautioned that implementing Doxy-PEP would not be without its costs for clinics.

The guidance suggests doctors can "prescribe enough doses of doxycycline to last until the next follow up visit." 

A list of considerations attached to the recommendation include a plea for doctors to assess for side effects that use of Doxy-PEP could be causing, as well as to screen every 3 to 6 months for the possibility of breakthrough infections.

"Larger evaluations can sometimes show negative outcomes that have been missed in smaller randomized trials. So we are going to be continuing to monitor and evaluate the implementation of Doxy-PEP over time," said Mermin.

Officials have also wrestled with the concern that Doxy-PEP could raise the risk of bacteria developing resistance to the antibiotic.

At a meeting hosted by the National Association of County and City Health Officials last year, experts warned it was possible widespread Doxy-PEP use could also lead to "collateral damage" in raising resistance for other pathogens beyond STIs as well.

The CDC is planning multiple efforts to track real-world implementation of Doxy-PEP, Mermin said, including monitoring for drug resistance.

"Given the gaps in science, long-term monitoring, evaluation and additional studies will be key for us to update the guidelines as needed. There are important questions that remain regarding potential risks," said Mermin.