STEVE INSKEEP, HOST:
Doctors have some advice for people who may be at risk for sexually transmitted infections. On any given day, 1 in 5 Americans has an STI. NPR's Will Stone reports on what to do.
WILL STONE, BYLINE: This next chapter in STI prevention comes down to a common run-of-the-mill antibiotic called doxycycline. It's already used to treat infections, including some STIs. The difference here is when you take it. Instead of waiting to be diagnosed with an STI, the medication is given out ahead of time so people can take it right after having unprotected sex. This approach is known as post-exposure prophylaxis, or PEP. So in this case, with doxycycline, it's doxy-PEP.
ANNIE LUETKEMEYER: We saw that this was safe. We saw that it was well tolerated. We saw that it reduced sexually transmitted infections.
STONE: That's Dr. Annie Luetkemeyer at the University of California, San Francisco. Luetkemeyer helped run a major clinical trial on doxy-PEP. It showed that those who took doxycycline 24 to 72 hours after sex without a condom had a 65% reduction in STIs, specifically syphilis, chlamydia and gonorrhea. And Luetkemeyer says this builds on other promising results from Europe.
STONE: It's not 100% whether there really are consistent reductions across the board.
STONE: So far research on doxy-PEP has focused on men who have sex with men and transgender women. Those in Luetkemeyer's study either had an HIV diagnosis or were taking the HIV prevention drug PrEP and had a history of STIs.
LUETKEMEYER: Our study does not inform everybody in the U.S. It informs a group of people who already had an elevated risk of sexually transmitted infections.
STONE: But she says in time, doxy-PEP could be used more broadly, regardless of someone's sexual orientation.
LUETKEMEYER: It's very reasonable to think about this for just men in general who are at higher risk of sexually transmitted infections.
STONE: The evidence doesn't yet support doing this for most women, though. A recent clinical trial had women in Kenya take doxy-PEP. Here's Dr. Jenell Stewart at Hennepin Healthcare.
JENELL STEWART: Unfortunately, in our study, we saw no reduction in STIs.
STONE: But Stewart says this is not the final word, and more research is needed.
STEWART: There's a clear need for STI prevention. And so it's incredibly disappointing that we don't have a solution to offer them right now.
STONE: Even so, health leaders are feeling optimistic about doxy-PEP. Dr. Leandro Mena leads STD prevention at the CDC.
LEANDRO MENA: We recognize that more tools are needed given the increased burden of gonorrhea, chlamydia and syphilis infection in the U.S.
STONE: He says the CDC is hoping to release guidance on doxy-PEP by the end of the summer, but some aren't waiting for that. Dr. Oliver Bacon works at the San Francisco City Clinic. He helped craft San Francisco's guidance for doxy-PEP and is now offering it to some of his patients.
OLIVER BACON: I would say interest has been very high.
STONE: Turns out people were already taking doxycycline on their own and not always in the ideal way.
BACON: They were just taking doxy randomly. I mean, it was sort of like doxy anarchy out there. And we don't want that to happen. That's not good for anybody. It doesn't treat the problem, and it certainly doesn't help issues of antibiotic resistance.
STONE: And that's the biggest hangup with doxy-PEP - what could it mean for antibiotic resistance? The clinical trial in the U.S. tried to get at this by looking for signs of increased resistance among those who took doxy-PEP. One concern was MRSA, a nasty bacteria that's sometimes treated with doxycycline. But there the researchers didn't find any worrying evidence. And surprisingly, doxy-PEP worked pretty well at curbing gonorrhea, even though many cases of gonorrhea are resistant to the class of antibiotics that doxycycline is a part of. Dr. Edward Hook, who's at the University of Alabama, Birmingham, says there's no STI pathogen with a greater propensity to develop resistance than gonorrhea.
EDWARD HOOK: I think it's reasonable to assume resistance rates for gonorrhea in particular will increase.
STONE: But Hook points out this well-known resistance is why other antibiotics are used for gonorrhea, and he's excited about doxy-PEP's potential.
HOOK: What we've been trying to do and our efforts to control STIs for the last 50 years have not succeeded. It's time to do something different.
STONE: And if the solution can be found in a cheap and widely available drug, all the better.
Will Stone, NPR News. Transcript provided by NPR, Copyright NPR.