As the number of sexually transmitted infections (STIs) sharply rises in the U.S., new evidence suggests that a common antibiotic—doxycycline—could help prevent the spread of some bacterial infections.
Based on results from new clinical trials, the Centers for Disease Control and Prevention (CDC) recently issued proposed guidelines for using doxycycline to reduce the risk of a chlamydia or syphilis—and possibly gonorrhea—infection among sexually active adults. Experts say new preventive approaches are critical to control the widening STI epidemic, fueled in part by the disruption in healthcare services during the height of the COVID-19 pandemic.
“Even before COVID started, we had seen a significant increase in STDs [sexually transmitted diseases], both internationally and here locally in California,” said Christopher Foltz, MD, an infectious disease specialist at Cedars-Sinai. “Syphilis has been climbing at the highest rate with a significant increase among pregnant women and men who have sex with men.”
Syphilis cases among men who have sex with men rose 7% from 2020 to 2021, according to the CDC. Syphilis rates among women jumped 55.3% from 2020 to 2021, and 217.4% from 2017 to 2021, which has led to the birth of more babies with the disease.
People with syphilis often don’t have symptoms, Foltz said, and when they finally visit a doctor, they may have been infected for months—or even years—without knowing it. Undiagnosed long-term infections can lead to permanent complications, including blindness and permanent neurologic damage.
“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.”
Old Drug, New Use
Doxycycline has long been a go-to treatment for acne, skin infections, illnesses spread by tics and pneumonia. The drug had been on the radar of physicians treating STIs for years, but previous clinical trials hadn’t shown it would be effective as a preventive therapy. Physicians have become increasingly hesitant to prescribe antibiotics when they’re not needed amid a rise in antibiotic-resistant bugs.
“Bacteria can figure out how to avoid being killed by antibiotics,” explained clinical pharmacist Greg Marks, PharmD, coordinator of the Antimicrobial Stewardship program at Cedars-Sinai Medical Center, which closely tracks the use of antibiotics in the hospital. “In general, the more we use antibiotics, the more concerned we are about resistance.”
But new trial results showed doxycycline could be an effective new tool to limit the spread of syphilis and chlamydia if taken as a single 200-milligram dose within 72 hours after unprotected sex, Marks said. Using doxycycline to prevent gonorrhea showed some promise but yielded mixed results.
Only one dose of the antibiotic is necessary in a three-day period to help avoid these bacterial infections, even if having sex with multiple partners. The strategy, dubbed “Doxy on Demand” or “Doxy-PEP” (post-exposure prophylaxis), is similar to taking the morning-after pill to prevent pregnancy after unprotected sex. But this new treatment isn’t a reason to ditch condoms.
“This by no means is a way to offset the use of condoms,” Foltz cautioned. “We absolutely encourage condom use to prevent against other STDs and HIV [human immunodeficiency virus] as an added barrier of protection for prevention.”
Foltz said the people most likely to benefit from this new strategy are those who have had STDs recently, those taking HIV medications or medications to prevent the spread of HIV, and members of the LGBTQ+ community, which tends to experience higher rates of certain STIs.
Pregnant women should generally avoid the drug, Marks said, as well as people allergic to tetracyclines, a class of antibiotics. He and Foltz encouraged patients to speak with a physician about whether doxycycline might be right for them.
“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,” Foltz said. “It comes down to each person’s individual risk level, something that you should discuss with your physician.”
Read more on the Cedars-Sinai Blog: Gaining Ground on HIV/AIDS