Want to receive publications straight to your inbox?

  • Doxycycline taken after sex reduces the risk of developing some sexually transmitted infections
  • Researchers interviewed participants in a clinical trial of doxycycline post-exposure prophylaxis
  • The drug provided peace of mind and gave people a sense of control over their sexual health

A well-designed clinical trial in the U.S. has found that doxycycline taken within 72 hours of sexual exposure significantly reduced the risk for developing chlamydia, gonorrhea and syphilis. The drug was effective in people with and without HIV. Participants in this study were gay, bisexual and other men who have sex with men (gbMSM) and transgender women. As a result of the trial, the U.S. Centers for Disease Control and Prevention (CDC) is finalizing guidance for healthcare providers about the deployment of doxycycline in these populations. When doxycycline is taken after exposure it is called post-exposure prophylaxis (PEP) and is generally abbreviated as doxyPEP.

Researchers interviewed 44 people (43 cisgender men and 1 transgender woman) who took part in the larger study of doxyPEP. Their average age was 38 years.  


The researchers stated that participants in the sub-study perceived doxyPEP as effective against the three bacterial sexually transmitted infections (STIs) previously mentioned. Participants expressed “confidence” in the preventive effects of the antibiotic.

One participant stated: “I’m kind of used to getting something in my urethra at least once a year…the fact that never happened [while on doxyPEP] just gives me some sort of idea that something was protecting me.”

The researchers stated that participants expressed that preventing STIs via doxyPEP was “highly preferable to treating an acquired STI, which they all had experienced in the past.”

The researchers included in the theme of acceptability the concept of ease of use of doxyPEP. They stated that “most participants were already accustomed to the routine of taking daily medications [either daily HIV pre-exposure prophylaxis or treatment for HIV].” They also stated that “many participants interviewed in this study reported a high level of personal organization that extended to their sex lives, which facilitated adherence to doxyPEP. Descriptions of ‘diligence’, such as ‘having a set of pills in my gym bag at all times,’ were particularly common.” Thus, for highly organized people, taking doxyPEP was relatively easy.

The researchers found that people who were “less organized with respect to planning ahead…had more difficulty.”


Most participants found doxyPEP easy to adhere to. However, some people reported confusion about the timing of the dose, particularly when there were multiple sexual partners within a short period of time.

Despite being told to take doxyPEP after condomless sex, including oral sex, the researchers found that several interviewees “were under the impression that they did not need doxyPEP for oral sex.” In part, this confusion arose because some participants perceived oral sex as safer than intercourse.

Side effects

According to the researchers, more than 50% of participants reported no side effects from the use of doxycycline. Other people reported side effects—mainly upset stomach or diarrhea. Affected participants generally described these side effects as temporary. In some cases, taking doxyPEP with food helped to reduce side effects.

Acceptability to sex partners

According to the researchers, “the majority of participants reported feeling supported by sex partners when discussing the use of doxyPEP.” Participants felt that this support arose because the community has become used to the biomedical prevention of infections, beginning with the increasing use of HIV pre-exposure prophylaxis (PrEP) in the past decade. Another factor participants noted was the knowledge arising from studies that found that people with HIV whose virus is suppressed because of treatment do not pass on the virus to their sexual partners (commonly abbreviated in the phrase undetectable = untransmittable, or U=U). Education about PrEP and U=U has permeated the community and this paved the way for acceptance of doxyPEP.

Mental health and quality of life

The researchers stated that “nearly all participants reported that doxyPEP had a positive impact on mental health and their quality of life.” They added that participants used terms such as “peace of mind/relief from worry over contracting and/or transmitting bacterial STIs, increased sense of control over [STI] transmission, and having a sense of supporting their own, sex partners’ and community health.”

One participant stated: “…it feels like [doxyPEP] gives a particular sense of security. It allows for a decrease in worry, you know? I’m a really active guy out there sexually.”

Another person said: “I can go and have sex with a lot less apprehension that I will transmit something back to my partners. Taking the doxy helped me relax more about being a bottom.”

One participant described to researchers how he felt taking doxyPEP: “I feel a little bit more like I’m doing everything I can to protect myself without having to compromise having the fun that I want to have, and that feels good.”

DoxyPEP gave many participants a sense of control over their sexual health. One participant framed it this way: “So, this kind of let me take a little bit more control…I don’t really have to ask you [STI and testing-related] questions. I’m taking as much precaution as I can for myself…”

Another person stated: “By participating in the study, I feel like I am kind of helping the rest of the community and the population in general do something about [STIs]…”

Bear in mind

The sub-study about the psychological and other impacts of the use of doxyPEP revealed many things. Most importantly, the use of doxyPEP had an overall positive impact on different aspects of sexual health for many people.

The research team encouraged healthcare providers to “not only clearly define the sexual circumstances for which doxyPEP should be used, but [they] may also need to remind patients in subsequent visits as part of ongoing conversation.” The team also is concerned that stigma associated with the use of doxyPEP could potentially arise in the future. Healthcare providers need to be aware of this possibility and address it when they encounter it.

Note that the overall study population for the larger doxyPEP clinical trial was what the researchers described as “highly organized.” The researchers stated that these participants underwent frequent STI testing, discussed recent STI test results with sexual partners, and kept diaries of partners and their contact information. The researchers stated that “for these men with a pre-existing strategy to support sexual and HIV-related health, doxyPEP was easy to integrate into daily routine.” However, the researchers stated that “those with less-organized approaches, that is, only accessing STI testing when symptomatic, reported more difficulty using doxyPEP or were less vocal about its benefits.” The researchers noted that these findings may be important to address as more healthcare providers prescribe doxyPEP.

The sub-study enrolled gbMSM and transgender women from urban areas of the west coast of the U.S. (the location of the larger doxyPEP study). More studies about doxyPEP acceptability and its impact need to be done in other regions and with other populations. People enrolled in the present study were also using HIV PrEP or HIV treatment. This made integration of doxyPEP into their lives easier. The researchers encouraged other scientists to explore the use of doxyPEP in people who are new to daily medication-taking.

—Sean R. Hosein


Doxycycline to help prevent bacterial STIs CATIE

Exploring the impact of doxycycline to prevent sexually transmitted infectionsCATIE News

Sexually transmitted and blood-borne infections: Guides for health professionals – Public Health Agency of Canada

Guidelines for the Use of Doxycycline Post-Exposure Prophylaxis for Bacterial STI Prevention – U.S. Centers for Disease Control and Prevention (CDC)

Post-exposure doxycycline helps reduce the risk for some sexually transmitted infections – TreatmentUpdate 249

Sexually transmitted infection testing interventions: community and service provider preferences – CATIE


Fredericksen RJ, Perkins R, Brown CE, et al. Doxycycline as postsexual exposure prophylaxis: Use, acceptability, and associated sexual health behaviors among a multi-site sample of clinical trial participants. AIDS Patient Care STDs. 2024 Apr;38(4):155-167.