Doxy PEP: Can Doxycycline Actually Prevent STIs After Sex?
Key takeaways:
Taking a dose of doxycycline (Vibramycin, Monodox, Acticlate) after sex may help prevent chlamydia, gonorrhea, and syphilis. But it’s not effective for other infections, including HIV.
Doxycycline post-exposure prophylaxis (“Doxy PEP”) is recommended for certain men who have sex with men and transgender women. It’s best used among those who have had a bacterial sexually transmitted infection (STI) within the past 12 months. You can take it as a single 200 mg dose within 72 hours (3 days) of oral, anal, or vaginal sex.
Doxy PEP reduces the risk of infection from certain STIs. But it’s not always guaranteed to work. You should always try your best to practice safe sex to maximize your health.
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Table of contents
Sexual health is an important part of the human experience. And just like every form of health, knowing how to maintain your sexual health is key. This sometimes comes down to preventing and treating sexually transmitted infections (STIs).
Preventing STIs is always a better bet than treating them. Safe sex practices, such as using condoms, are highly recommended for everyone who has sex. But some people also benefit from medications that help prevent STIs. Pre-exposure prophylaxis (PrEP) medications for HIV are a common example.
More recently, an antibiotic called doxycycline has gained popularity as a way to prevent certain bacterial STIs. This strategy is called “Doxy PEP.” Here, we'll do a dive deep into Doxy PEP and if you should consider trying it.
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What is Doxy PEP?
Doxy PEP is a newer way to take an old medication. The term is a combination of two phrases, doxycycline and PEP.
Doxycycline (Vibramycin, Monodox, Acticlate) is a prescription antibiotic that’s used to treat bacterial infections.
PEP stands for post-exposure prophylaxis. PEP medications are helpful if you think you’ve been exposed to a germ that can make you sick.
If you’ve been exposed to an STI-causing bacteria during sex, the idea is that a dose of doxycycline will help prevent an infection. The type of doxycycline shouldn’t make a difference.
Good to know: Although PrEP and PEP can both prevent illness, there’s a difference between the two. You take PreP medications before being exposed to a germ that may make you sick. PEP is taken after you’re potentially exposed.
Making safe sex a priority: Condoms are an effective way to prevent unwanted pregnancies and STIs. Learn about the several types of condoms available to find one that works for you.
Test, treat, go: Many STIs today can be treated or cured with medication. Here’s what to do if you test positive for a STI.
Is anal sex safe? Yes, in general. Read on to discover best practices for anal sex safety.
Does research support taking doxycycline for STI prevention?
Yes. Current research suggests that Doxy PEP is effective for bacterial STI prevention. The CDC officially recommended Doxy PEP as a STI prevention tool in June 2024.
Several studies back up this recommendation. For instance, one study found that taking doxycycline after a sexual encounter reduced the risks of developing chlamydia and syphilis by over 70%. The risk of gonorrhea went down by more than 50%. Everyone in the study was either living with HIV or taking PrEP medications to prevent it.
Doxy PEP has been shown to benefit certain groups of people who have had a bacterial STI within the past 12 months (1 year). These include men who have sex with men and transgender women. However, in some cases, healthcare professionals may prescribe Doxy PEP even without a recent STI diagnosis. It may also benefit people within these groups who have multiple sexual partners.
Doxy PEP’s effectiveness for other people is less clear. There isn’t much supporting data for cisgender women, straight cisgender men, transgender men, and other nonbinary people. If you identify with one of these groups, your healthcare professional will make the final call on if Doxy PEP is worthwhile or not.
Doxycycline dosages for post-exposure prophylaxis
To use Doxy PEP, you’ll take one 200 mg dose of doxycycline. It’s best to take it within 72 hours (3 days) of oral, anal, or vaginal sex. But it’s most effective if you take it within 24 hours (1 day) of sex. This is different from how doxycycline is normally taken to treat bacterial infections.
You should take doxycycline with a glass of water and avoid lying down for 1 hour afterwards. If you know doxycycline upsets your stomach, you can take it with food to make your symptoms less intense. Don’t take more than 200 mg in a 24-hour period, either.
Good to know: You’ll likely need to see a healthcare professional every 3 to 6 months while taking Doxy PEP. They’ll want to do routine testing and make sure that you’re still benefiting from doxycycline before offering another refill.
Are there any downsides to Doxy PEP?
Doxy PEP isn’t perfect. It doesn’t work for every type of STI. It’s most helpful for preventing chlamydia, syphilis, and gonorrhea. Doxy PEP can’t prevent infection from other types of STIs. This includes viruses such as HIV, Mpox, herpes simplex, and more.
Some evidence also suggests that Doxy PEP may increase the risk of antibiotic resistance. This means that it could make infections harder to treat in the future because bacteria learn to adapt to antibiotics. These stronger bacteria — dubbed “superbugs” — can cause harder-to-treat infections.
Doxycycline side effects are possible, too. These include stomach upset, a burning feeling in the throat, and sun sensitivity. The good news is that these side effects go away when you aren’t taking the medication, and they tend to be short lived. Most people can take doxycycline without experiencing any problems at all.
What’s more, Doxy PEP isn’t 100% effective. It simply lowers the risk of infection. For that reason, it shouldn’t replace other safe sex practices.
How to get Doxy PEP
If you’re curious about how to get Doxy PEP, the best place to start is with your healthcare professional. Together, the two of you can decide if Doxy PEP is the right option for you based on your lifestyle and medical history.
If you don’t have a designated healthcare professional (or if they’re not available), other options are available too. Several companies offer Doxy PEP prescriptions online through telehealth services. Plus, some health clinics may provide Doxy PEP for free or at a low cost, depending on your ability to pay.
Can any other antibiotics prevent STIs?
No. At this time, no other antibiotics are widely recommended to prevent STIs. They haven’t been studied the same way as doxycycline. In fact, taking antibiotics other than how they should be prescribed is a potential public health risk. Improper use can increase the rate of antibiotic resistance.
How can you prevent STIs without medication?
Not having sex (abstinence) is the only guaranteed way of preventing an STI. But if you’re sexually active, barriers such as condoms are effective in preventing the transmission of STIs, too.
There are also actions you can take before having sex that reduce the risk of STIs. Limiting your number of sexual partners helps lower the odds of being exposed to an STI. And if you change sexual partners, try having a conversation about safe sexual practices and testing for STIs before you have sex. Knowledge and transparency is your best protection against a surprise diagnosis.
The bottom line
Doxy PEP, or taking a preventative dose of doxycycline after sex, is an effective and CDC-recommended way to reduce the risk of illness from chlamydia, syphilis, and gonorrhea. It doesn’t reduce the risk of other infections, such as HIV. It has been studied most in men who have sex with men and transgender women. It’s generally safe to take, but it can cause side effects such as stomach upset. Doxy PEP isn’t 100% effective at preventing STIs, either. But it can be a helpful option if other safe sex practices fall through.
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References
Bachmann, L. H., et al. (2024). CDC clinical guidelines on the use of doxycycline postexposure prophylaxis for bacterial sexually transmitted infection prevention, United States, 2024. Centers for Disease Control and Prevention.
Centers for Disease Control and Prevention. (2024). Primary prevention methods.
Gonzalez, L. L. (2023). Don’t take chances: Why doxycycline is a great bet against STIs. University of California San Francisco.
Kenyon, C., et al. (203). Doxycycline PEP can induce doxycycline resistance in Klebsiella pneumoniae in a Galleria mellonella model of PEP. Frontiers in Microbiology.
Traeger, M. W., et al. (2023). Potential impact of doxycycline post-exposure prophylaxis prescribing strategies on incidence of bacterial sexually transmitted infections. Clinical Infectious Diseases.
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