NIH-funded study finds doxycycline reduces sexually transmitted infections by two-thirds

April 10, 2023
Participants were randomly assigned to receive either doxy-PEP or standard of care.

The oral antibiotic doxycycline prevented the acquisition of sexually transmitted infections (STIs) when tested among men who have sex with men (MSM) and transgender women who took the medication within 72 hours of having condomless sex, according to findings published in the New England Journal of Medicine.

Specifically, the post-exposure approach, termed doxy-PEP, resulted in a two-thirds reduction in the incidence of syphilis, gonorrhea, and chlamydia among the study participants, all of whom reported having an STI within the previous year. However, the research also revealed a slight increase in antibacterial resistance that requires further exploration the authors found. The research was funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

The study was led by researchers at the University of California at San Francisco (UCSF) and the University of Washington, Seattle. It enrolled 501 adults at four clinic sites in San Francisco and Seattle who were at least 18 years of age; assigned male sex at birth; reported sexual activity with a man in the previous year; diagnosed with HIV or taking or planning to take pre-exposure prophylaxis (PrEP) medication to prevent HIV acquisition; and diagnosed with gonorrhea, chlamydia or early syphilis in the prior year. Of those enrolled, 327 participants were taking HIV PrEP medications, and 174 participants were people living with HIV.

NIH release