In June 2024, the Centers for Disease Control and Prevention issued guidelines for the use of the oral antibiotic doxycycline as a post-exposure preventative treatment, known as DoxyPEP, against certain sexually transmitted infections. Like the morning-after pill to prevent pregnancy after unprotected sex, DoxyPEP is taken after unprotected sex to prevent STIs like chlamydia, gonorrhea, and syphilis. (That’s why some sources refer to it colloquially as a “morning-after pill” for STIs.)
Between 2017 and 2021 in the U.S., cases of syphilis increased by 74 percent, and cases of gonorrhea increased by 28 percent.
“DoxyPEP is a response to this rise in infections,” says Dr. Oliver Bacon, an infectious disease specialist and medical director of San Francisco City Clinic. “It offers people a new way to reduce their risk of getting and transmitting gonorrhea, chlamydia, and syphilis.”
Read on to learn more about DoxyPEP: how it works, which STIs it protects against, who should take it, and more.
How does DoxyPEP work?
Doxycycline is an antibiotic that treats and prevents some bacterial STIs. When taken orally within 72 hours after unprotected sex, DoxyPEP is very effective at protecting against chlamydia and syphilis. It is also somewhat effective at protecting against some strains of gonorrhea.
DoxyPEP does not protect against other viral diseases that can be transmitted sexually like HIV, HPV, mpox, or herpes.
Recent randomized controlled trials have demonstrated that for cisgender men who have sex with men and for transgender women, taking 200 mg of doxycycline within three days after unprotected sex decreased the incidence of syphilis and chlamydia by 70 to 85 percent and decreased the incidence of gonorrhea by around 50 percent.
A 2023 study found that DoxyPEP was not effective in cisgender women. However, while participant-reported adherence was high, random hair samples revealed that many participants may have not taken the antibiotic. More research is needed to determine the efficacy of DoxyPEP in cisgender women and transgender men.
Who should take DoxyPEP and when?
The CDC recommends DoxyPEP for cisgender men who have sex with cisgender men and transgender women with a history of at least one bacterial STI in the previous 12 months.
San Francisco City Clinic has been offering DoxyPEP to patients since November 2022.
“We offer DoxyPEP to cisgender men, transgender women, and [transgender] men who have either had gonorrhea, chlamydia, or syphilis in the last year or have had at least two condomless sexual partners in the last year,” says Bacon. “Even in the absence of studies that include trans men, we felt that the benefits-to-risk ratio of offering DoxyPEP came down in favor of offering it to them.”
DoxyPEP should be taken within 72 hours of having penetrative or oral sex without a safer sex barrier. But unlike the morning-after pill for pregnancy prevention, you need a prescription to get DoxyPEP.
How do you get a prescription for DoxyPEP, and how much does it cost?
You need to have DoxyPEP on hand before having unprotected sex in order to take the medication within the 72 hour time window. If you are a cisgender man who has sex with men, a transgender woman, or a transgender man, talk to a health care professional about whether DoxyPEP is right for you.
If you’re uninsured or if your insurance does not cover DoxyPEP, the out-pocket-cost for 200 mg of doxycycline is around $13, but you may be able to get it for less through discount programs, like GoodRx.
“Cost isn’t a barrier given that doxycycline is generic and quite inexpensive,” says Dr. Annie Luetkemeyer, a professor of medicine and infectious diseases at the University of California, San Francisco, who led a clinical trial on DoxyPEP.
How often can you safely take doxycycline to protect against STIs?
It’s safe to take doxycycline multiple days in a row, but you shouldn’t take more than 200 mg within a 24-hour period.
What are the side effects of doxycycline?
The most commonly reported side effects of doxycycline are headaches, nausea, vomiting, and diarrhea. Doxycycline may cause your skin to be more sensitive to sunlight, so it’s important to wear sunscreen and reduce sun exposure after taking this medication.
What are other practices that can reduce the risk of contracting an STI?
Anyone who has vaginal sex, anal sex, oral sex, or genital skin-to-skin contact or who shares sexual fluids with other people can contract an STI. There are other steps you can take to prevent a wider range of bacterial STIs and sexually transmitted viruses.
These prevention methods are effective in people of all genders:
- Use barriers like condoms and dental dams during vaginal, anal, and oral sex.
- Get vaccinated against hepatitis B and HPV, which can both be transmitted through sexual contact. The hepatitis B vaccine is recommended for everyone 59 and younger and for adults 60 or older with risk factors for hepatitis B infection. The HPV vaccine is recommended for adolescents of any gender. Anyone between the ages of 9 and 45 can receive it.
- Get tested for STIs regularly and ask your sexual partners to get tested regularly.
- Talk to your doctor about pre-exposure prophylaxis (PrEP), a daily medication that can reduce your risk of contracting HIV through sex by 99 percent.
“My hope is that DoxyPEP gets incorporated into a comprehensive sexual health package,” says Luetkemeyer. “This is a useful tool that people can add on at times of elevated risk when it makes sense for them.”
For more information, talk to your health care provider.