‘Doxy PEP’ can help prevent bacterial STIs in certain high-risk patients

The U.S. Centers for Disease Control (CDC) is now recommending the use of doxycycline postexposure prophylaxis (doxy PEP) as a strategy to prevent bacterial sexually transmitted infections (STIs) in men who have sex with men (MSM) and transgender women (TGW) who have had a bacterial STI (syphilis, chlamydia or gonorrhea) diagnosed in the past 12 months. These STIs are increasing in the United States and disproportionately affect gay, bisexual and other MSM, as well as TGW.1Following shared decision-making with their healthcare provider, MSM and TGW should be offered a prescription for doxy PEP to be self-administered within 72 hours after having oral, vaginal or anal sex. The recommended dose of doxy PEP is 200 mg (2 x 100 mg) and should not exceed a maximum of one 200 mg dose every 24 hours. Prescriptions should be written for enough doses, based on the person’s anticipated sexual activity until their next visit.1In three large randomized controlled trials in MSM and TGW, doxycycline 200 mg taken within 72 hours after sex has been shown to reduce syphilis and chlamydia infections by > 70% and gonococcal infections by about 50%.1The CDC recommends use of doxy PEP in combination with other risk reduction measures, including risk reduction counselling (e.g., use of condoms), STI screening and treatment, recommended vaccination and linkage to HIV pre-exposure prophylaxis (HIV PrEP), HIV care, or other services as appropriate. Persons prescribed doxy PEP should undergo bacterial STI testing at anatomic sites of exposure at baseline and every three to six months thereafter. Ongoing need for doxy PEP should be assessed every three to six months. HIV screening should be performed for HIV-negative MSM and TGW according to current recommendations.1Possible harms or unknowns from use of doxy PEP include:Gastrointestinal side effects/intoleranceFacilitation of antimicrobial resistance in bacterial STIs and other common bacterial pathogens (e.g., Staphylococcus aureus). Unknown impact on the human microbiome (i.e., the microorganisms performing essential functions for immune development, defense against pathogens, and nutrient metabolism).Potential harms appear low in the short term, but are unknown and potentially concerning in the long term. Ongoing studies are evaluating doxy PEP, including the risk for the development of antimicrobial resistance.1Although the CDC does not specifically recommend the use of doxy PEP in other populations, it could be discussed with MSM and TGW who have not had a bacterial STI diagnosed during the previous year, but who will be participating in sexual activities that are known to increase the likelihood of exposure to STIs. In addition, the pharmacokinetics of doxycycline and experience in treating bacterial STIs suggest that doxy PEP should be effective in other populations (e.g., cisgender women, cisgender heterosexual men, transgender men, and other queer and nonbinary persons assigned female at birth), but evidence is insufficient to assess the balance of benefits and harms in these populations. Therefore, the CDC has not made a recommendation for use in these groups and suggests that healthcare providers use their clinical judgement and shared decision-making to inform use of doxy PEP in these situations.1 Currently no Canadian national guidelines are available on the use of doxycycline for STI prophylaxis.2 However, the BC Centre for Disease Control (BCCDC) issued a position statement in October 2023, advising that doxy PEP can be considered for gay, bisexual and other MSM and transgender women who have had a bacterial STI in the previous year.3 The BCCDC statement suggests providing a prescription (with refills), with instructions to take doxycycline 200 mg (2 x 100 mg capsules) within 72 hours of condomless sex, with no more than one dose to be taken per day. BCCDC suggests that patients be counselled using the “3-2-1 rule”—take within 3 days of sex, 2 tablets, and no more than 1 dose per day. Patients should be advised to take doxycycline with a full cup of water, and to remain upright for at least 30 minutes following administration, to minimize gastrointestinal symptoms (e.g., reflux).3Overall, doxy PEP has the potential to benefit the health of MSM and TGW through STI prevention, reduced patient anxiety, and improved sexual health and well-being.3References: 1. Bachmann LH, Barbee LA, Chan P, et al. CDC clinical guidelines on the use of doxycycline postexposure prophylaxis for bacterial sexually transmitted infection prevention, United States, 2024. MMWR 2024;73(2);1-8. (accessed July 16, 2024).2. CATIE. Doxycycline to help prevent bacterial STIs. (accessed July 16, 2024).3. BC Centre for Disease Control. The BCCDC position statement on doxycycline as prophylaxis for sexually transmitted infections. October 27, 2023. (accessed July 16, 2024).

‘Doxy PEP’ can help prevent bacterial STIs in certain high-risk patients

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