Patients who took the antibiotic doxycycline after sexual exposures saw a “dramatic” decline in syphilis and chlamydia, according to a new Kaiser Permanente study.
The analysis, published in JAMA Internal Medicine, looked at a program offering the antibiotic to Kaiser Permanente Northern California patients for the prevention of sexually transmitted infections (STIs). Using doxycycline as a preventive measure for STIs is a method known as doxyPEP.
The study included those who also receive HIV preexposure prophylaxis (PrEP) medication to prevent HIV, since many of these patients are also at increased risk for other STIs.
Since being introduced in late 2022, doxyPEP has become the standard of care for preventing STIs for Kaiser Permanente patients on PrEP or with an HIV diagnosis.
“Our patients have enthusiastically embraced this proactive approach to reduce their STI risk,” said study co-author Jonathan Volk, MD, MPH, an infectious diseases physician with Kaiser Permanente Northern California. “After doxyPEP became available for our PrEP patients, we have seen a dramatic decline in positive STI tests and less need for treatment after STI exposures.”
Almost 1 in 5, or 2,253 eligible people, filled prescriptions for doxyPEP since November 2022. The study compared bacterial STI infections in the patients before they received a doxyPEP prescription and after. The researchers found incidence declined 79% for chlamydia, 80% for syphilis, and 12% for gonorrhea.
Gonorrhea cases didn’t decline as much as cases of chlamydia and syphilis. The initial clinical trials for doxyPEP saw a bigger reduction in gonorrhea cases, Dr. Volk pointed out. The reasons for this difference were not immediately clear, but the lower results may reflect changes in antibiotic resistance.
“These modest reductions in gonorrhea rates reinforce the importance of regular STI testing for patients on doxyPEP and the need for novel strategies for gonorrhea prevention, such as the vaccines that are currently in development,” he said.
New approaches are needed to counter a worrying increase in STIs in recent years, said co-author Michael Silverberg, PhD, MPH, an HIV epidemiologist with the Kaiser Permanente Division of Research.
“Rising syphilis rates highlight the urgent need for innovative tools like doxyPEP,” Silverberg said.
Prevention is one important way to tackle the problem, Dr. Volk noted. “The rise in STIs has been an ongoing challenge. Having more tools at our disposal to reduce incidence is critical.”
