Doxycycline in STI Prophylaxis—A Literature Review

Background: Since the implementation of pre-exposure prophylaxis (PrEP) in HIV prevention, a significant increase in the prevalence of other sexually transmitted infections (STIs) has been reported, especially among men who have sex with men (MSM). Doxycycline is being examined as a potential pharmacological agent in preventing these infections. This review aims to summarize available data on the effectiveness and potential side effects of doxycycline for the prevention of bacterial STIs. Methods: We reviewed the National Library of Medicine and the National Center of Biotechnology Information in order to find clinical trials and relevant observational studies regarding doxycycline usage in STI prophylaxis. Results: Doxycycline prophylaxis reduced the risk of acquiring chlamydia, syphilis, and, in a majority of the trials, the risk of gonorrhea. The clinical trials on doxycycline STI prophylaxis were underpowered to determine if doxycycline promotes the selection of resistance in Neisseria gonorrhoeae and Chlamydia trachomatis. Additionally, no serious side effects of this preventive measure have been reported. None of the studies aimed to compare the efficacy of post- and pre-exposure prophylaxis of STDs with doxycycline. Conclusions: The preliminary results regarding STI prophylaxis with doxycycline seem to be promising. Further research is needed to determine the potential risk of doxycycline prophylactic prescription.