A study of more than 2,000 patients in Los Angeles who were prescribed doxycycline post-exposure prophylaxis (DP) found it was highly effective in preventing sexually transmitted infections (STIs), researchers reported last week in Open Forum Infectious Diseases.
For the study, conducted at the Los Angeles LGBT Center from April 2019 to July 2024, researchers analyzed electronic health record data on 2,083 patients who were prescribed DP over the study period. The center issued formal clinician guidance on DP use in October 2022. The aim of the study was to review patient demographics, STI testing history, use patterns, and short-term effectiveness of DP.
Nearly half of the patients were between 31 and 40 years of age (48.1%), over half were white (55.9%), 85.2% were gay or bisexual men, and 41.4% had a history of one or more STI diagnoses in the year prior to DP initiation. Nearly a quarter (24.5%) of DP patients received a prescription from January 1 to April 15, 2024.
Real-world efficacy matches clinical trial results
Among 1,115 patients with 6 months or more of DP use, cases of syphilis fell by 86.4%, chlamydia cases declined by 89.7%, and gonorrhea cases decreased by 54.7%. There was similar effectiveness for chlamydia and gonorrhea regardless of anatomic site (rectal or throat swabs or urine sample).
The study authors note that the reduction in bacterial STIs observed among DP users is similar to the results of the DoxyPEP trial conducted in San Francisco and Seattle. Results from that trial and another in France resulted in the Centers for Disease Control and Prevention recommending DP in 2024 for gay men and transgender women with a history of STIs.
The authors say that while DP has become "an important and ever more widely used tool" for bacterial STI transmission, important questions about possible tradeoffs or consequences of consistent use remain.
"Researchers should closely examine use patterns and establish quality improvement programs in all settings where DP use is recommended in order to minimize adverse outcomes while trying to achieve population impact on the STI and HIV syndemics," they concluded.