SATURDAY, Nov.18Data showing that the antibiotic doxycycline might prevent a sexually transmitted infection (STI) if taken soon after sex made headlines earlier this year.

As surging numbers of cases of syphilis and gonorrhea affect more Americans, here’s what you need to know about using the drug.

“If you’re actively having sex and not using condoms 100% of the time, which is the reality out there, this strategy could be appropriate for you,” said Dr. Christopher Foltz, an infectious disease specialist at Cedars-Sinai in Los Angeles. “It comes down to each person’s individual risk level, something that you should discuss with your physician.”

He noted that syphilis, especially, has reemerged with a vengeance in recent years as a health threat.

 “Syphilis has been climbing at the highest rate with a significant increase among pregnant women and men who have sex with men,” Foltz said in a hospital news release.

According to the U.S. Centers for Disease Control and Prevention, syphilis cases among gay and bisexual men in the United States rose by 7% between 2020-2021.

Rates of new cases of the disease rose even more steeply among women: a 55.3% jump between 2020 and 2021, and 217.4% rise between 2017 and 2021 overall. That means more babies potentially being born with syphilis, as well.

You may not even realize you are infected with syphilis, Foltz noted, since in many cases it can lurk symptom-free for years. But left undiagnosed, long-term syphilis can cause blindness and neurological issues.

“That’s what we’re trying to prevent — these kinds of catastrophic long-term complications from undiagnosed STIs,” Foltz said. “If we can prevent infections with a relatively safe and easy-to-take antibiotic, the overall number of new infections will ultimately decrease.”

That’s why the new data on doxcycycline is so promising. A trial found that one 200 milligram (mg) dose of the drug — which has been used to treat other ailments for years — could prevent infection with syphilis and chlamydia if taken within 72 hours of a sexual encounter.

The strategy has even gained a nickname: “Doxy on Demand” or “Doxy PEP” (post-exposure prophylaxis).

The method isn’t foolproof however, and it’s no reason to forgo the use of condoms, Foltz warned.

“We absolutely encourage condom use to prevent against other STDs and HIV as an added barrier of protection for prevention,” he stressed.

Doxycycline is not advised for certain groups: Pregnant women and anyone known to be allergic to a class of antibiotics known as tetracyclines. Always consult with your doctor before taking any antibiotic.

More information

Find out more about syphilis at the CDC.

SOURCE: Cedars-Sinai Los Angeles, news release, Nov. 2, 2023