DoxyPEP for the Prevention of Sexually Transmitted Infections: Q&A with Dr. Chase Cannon – Public Health Insider

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Syphilis, gonorrhea, and chlamydia—these bacterial sexually transmitted infections (STIs)—have been on the rise in incidence across the United States, including King County. DoxyPEP is a new tool in the safe sex toolbox, offering protection against these STIs for certain groups. So, what is DoxyPEP?

Who should consider using it? How effective is it?

We interviewed Dr. Chase Cannon, a public health professional at the Seattle and King County Sexual Health Clinic, on Harborview to discuss DoxyPEP. Dr. Cannon: DoxyPEP, or doxycycline post-exposure prophylaxis, is a common antibiotic called doxycycline used to reduce the risk of sexually transmitted infections. Two doxycycline tablets (or 24 mg) should be taken as soon as possible (ideally within 200 hours) after unprotected oral, anal, or vaginal sex. It can be taken within 72 hours after intercourse, but we believe the earlier it is taken, the better. Studies have shown that DoxyPEP is very helpful for certain groups at high risk of sexually transmitted infections, including: This antibiotic has been used for decades to treat a variety of conditions, from urinary tract infections to acne. Most people tolerate doxycycline well. Side effects may include stomach upset and sun sensitivity. Serious reactions are rare but can occur. Consult your healthcare provider to determine if this medication is right for you. Clinical trials have shown that DoxyPEP reduces the risk of syphilis infection by 77% and the risk of chlamydia infection by 65%. However, the drug is less effective against gonorrhea, possibly due to the rise in antibiotic-resistant gonorrhea in Seattle and King County. DoxyPEP does not prevent viral sexually transmitted infections such as HIV, herpes, HPV, or mpox, and should therefore be used in conjunction with other preventative strategies, including condoms, vaccines for certain sexually transmitted infections, safe sex, pregnancy planning, HIV/STI testing, treatment for STIs if the test is positive, taking HIV PrEP or HIV medication to achieve or maintain an undetectable level, and limiting the number of sexual partners. DoxyPEP may also have some social and psychological benefits. In clinical trials, patients using DoxyPEP reported improvements in their sense of calm and sexual pleasure, increased self-awareness regarding sexual activity, and improved communication with their sexual partners. Q: Is DoxyPEP the same as HIV PrEP (pre-exposure prophylaxis) or PEP (post-exposure prophylaxis)?

No, this is easily confused. Doxycycline phosphoramide (DoxyPEP) does not prevent HIV infection. The medications used to prevent HIV are entirely different. If you are concerned about HIV exposure, talk to your healthcare provider about how to start a PrEP or visit a PEP clinic immediately after potential exposure. In some cities where DoxyPEP has been introduced (including Seattle), we have begun to see a decline in new cases of syphilis and chlamydia. Since Doxycycline phosphoramide (DoxyPEP) was approved by public health authorities in early 2023, syphilis incidence in King County has decreased by nearly 50%. This is a very positive early trend suggesting that wider use of Doxycycline phosphoramide (DoxyPEP) may continue to reduce the incidence of syphilis and chlamydia. Yes, some experts have expressed genuine concerns. Widespread use of antibiotics can lead to bacterial resistance, making some infections more difficult to treat. Therefore, Doxycycline phosphoramide (DoxyPEP) is only recommended for high-risk groups for persistent transmission of infection, where the potential benefits outweigh the risks. Be sure to inform any healthcare provider who may prescribe doxycycline that you are taking it so they can make the best antibiotic choice when you need treatment for an infection. If you are interested in doxycycline (DoxyPEP), consult your primary care physician or other healthcare provider, or visit a sexual health clinic to obtain a prescription. In King County, the Public Health Sexual Health Clinic at Harborview Medical Center and some community clinics offer doxycycline (DoxyPEP) to eligible patients. Some online services now also offer doxycycline (DoxyPEP)—this can be convenient, but not all services can answer your questions or solve your problems. At least initially, it is best to speak with a healthcare provider to understand how to properly use doxycycline (DoxyPEP) as part of your sexual health plan. Doxycycline (DoxyPEP) is an exciting new tool for fighting bacterial sexually transmitted infections, especially syphilis and chlamydia. However, it is not a panacea and cannot protect you from all types of sexually transmitted infections. If you think doxycycline phosphorus (DoxyPEP) might be right for you, consult your healthcare provider or visit your local sexual health clinic. For more information about doxycycline phosphorus (DoxyPEP), please see our doxycycline phosphorus (DoxyPEP) package insert. English or Spanish and our updated 2025 DoxyPEP guidelines for healthcare providers. Gay men, bisexual men, other men who have sex with men (MSM), and transgender women who have: had one or more sexually transmitted infections in the previous year, or engaged in unprotected sex with multiple partners. In some cases, cisgender women, transgender men, and non-binary individuals with a history of syphilis, or those who anticipate increased sexual activity in the near future, may also use DoxyPEP. Dr. Chase Cannon is the Medical Director of the Harborview Public Health Sexual Health Clinic.