Doxycycline effectiveness against STIs

Doxycycline effectiveness against STIs | Image Credit: © Kzenon - © Kzenon - stock.adobe.com.

Doxycycline postexposure prophylaxis is effective at reducing sexually transmitted infections (STIs) among transgender women and men who have sex with men (MSM), according to a recent study published in The New England Journal of Medicine.

In the open-label, randomized study, participants were divided into 2 groups. The first was comprised of those taking preexposure prophylaxis (PrEP) to prevent human immunodeficiency virus (HIV) infection and the other those living with HIV infection who had Neisseria gonorrhoeae (gonorrhea), Chlamydia trachomatis (chlamydia), or syphilis within the past year.

Patients from both cohorts were randomly assigned 2:1 to receive either doxycycline 200 mg or standard care without doxycycline within 72 hours following condomless sex. Incidence of 1 or more STI was the primary outcome of the study, measured through quarterly STI testing.

There were 501 participants overall, 327 in the PrEP group and 174 in the HIV infection cohort. Sixty-seven percent of participants were White, 30% Hispanic or Latino, 11% Asian or Pacific Islander, and 7% Black.

An STI was diagnosed during 10.7% of quarterly visits for individuals in the PrEP cohort taking doxycycline and 31.9% for individuals in the PrEP cohort receiving standard care. This data measured an absolute difference of -21.2% and a relative risk of 0.34.

For those living with HIV, 11.8% of quarterly visits led to an STI diagnosis for individuals taking doxycycline and 30.5% for individuals receiving standard care. This data measured an absolute difference of -18.7% and a relative risk of 0.38.

Doxycycline was associated with a decreased incidence of gonorrhea, chlamydia, and syphilis compared to standard care. In the PrEP cohort, gonorrhea had a relative risk of 0.45, chlamydia 0.12, and syphilis 0.13. In the living with HIV cohort, gonorrhea had a relative risk of 0.43, chlamydia 0.26, and syphilis 0.23.

There were 5 grade 3 adverse events linked to doxycycline, none of which were severe. Doxycycline postexposure prophylaxis lowered gonorrhea, chlamydia, and syphilis incidence by two-thirds, supporting use in MSM and transgender women with recent bacterial STIs.

Reference

Luetkemeyer AF, Donnell D, Dombrowski JC, et al.Postexposure Doxycycline to Prevent Bacterial Sexually Transmitted Infections. N Engl J Med. 2023;388:1296-1306. doi:10.1056/NEJMoa2211934