TL;DR
Doxy-PEP is 200mg of doxycycline taken within 72 hours after sex (ideally within 24 hours) to prevent bacterial STIs. Evidence shows roughly 70–90% reduction in chlamydia and syphilis, with modest protection against gonorrhea. The CDC formally endorsed doxy-PEP in June 2024 for cisgender men who have sex with men (MSM) and transgender women who had a bacterial STI in the past year. Doxycycline is a generic antibiotic that's cheap (~$10–$30 cash for a typical supply). Telehealth services like MISTR offer doxy-PEP prescriptions and can often coordinate $0 access.
What is doxy-PEP?
Doxy-PEP stands for doxycycline post-exposure prophylaxis. The protocol is simple: take a single 200mg dose of oral doxycycline (typically two 100mg tablets) within 72 hours after condomless oral, anal, or vaginal sex. The dose prevents the bacterial STIs — chlamydia, syphilis, and some strains of gonorrhea — from establishing infection.
Unlike daily PrEP for HIV or daily antibiotics for STI prophylaxis, doxy-PEP is event-driven. You only take it after sex, not every day. That makes it a practical addition to a broader sexual health toolkit for people with recurrent bacterial STIs.
Doxycycline has been a commonly prescribed antibiotic for decades — used for acne, Lyme disease, malaria prophylaxis, and many bacterial infections. Its safety profile is well-established. The doxy-PEP use is newer and still being studied, but it's now an established tool in the CDC's STI prevention guidelines.
How effective is doxy-PEP?
Clinical trial data is strong for MSM and transgender women. Here are the key results:
| STI | Risk reduction (MSM/trans women) |
|---|---|
| Chlamydia | ~88% reduction |
| Syphilis | ~87% reduction |
| Gonorrhea | ~55% reduction (variable by region) |
The gonorrhea numbers are less consistent across studies, largely because of tetracycline resistance in some gonorrhea strains. In regions where gonorrhea has higher baseline tetracycline resistance (including parts of the U.S.), doxy-PEP's gonorrhea protection is weaker. For chlamydia and syphilis — both of which remain doxycycline-susceptible nearly everywhere — protection is very strong.
For cisgender women, the evidence is mixed. A trial in Kenyan cisgender women (dPEP Kenya study) didn't show clear protection, possibly due to differences in STI type distributions, genital microenvironment, and adherence patterns. The CDC's current doxy-PEP guidance specifically endorses the protocol for MSM and transgender women — not cisgender women, until further evidence emerges.
Who should consider doxy-PEP?
The CDC's 2024 guidelines recommend doxy-PEP for:
- MSM (cisgender men who have sex with men) who've had a bacterial STI (chlamydia, gonorrhea, or syphilis) in the past 12 months
- Transgender women who've had a bacterial STI in the past 12 months
Many providers interpret this broadly, offering doxy-PEP to MSM and transgender women at elevated STI risk even if they haven't had a diagnosed STI in the past year. The risk-benefit balance generally favors offering it to people who would benefit clinically.
For cisgender women, bisexual women, and others not currently in CDC guidelines, doxy-PEP remains an off-label consideration to discuss with a provider.
Get doxy-PEP prescribed online in about 15 minutes
MISTR providers can prescribe doxy-PEP after a short intake. Doxycycline fills at any pharmacy for $10–$30 cash, or often $0 through MISTR's 340B partnerships.
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How do I take doxy-PEP?
The standard protocol:
- Dose: 200mg of doxycycline (typically two 100mg tablets or one 200mg hyclate/monohydrate tablet)
- Timing: Within 72 hours after condomless oral, anal, or vaginal sex. Within 24 hours is ideal; same-day is best.
- Frequency cap: Generally, no more than one 200mg dose per 24-hour period regardless of number of sexual encounters
- With food: Doxycycline can cause stomach upset. Take with food and a full glass of water. Don't lie down immediately after — sit upright for at least 30 minutes to prevent esophageal irritation
Doxycycline interacts with certain products. Specifically, dairy products, antacids containing calcium/magnesium/aluminum, and iron supplements can significantly reduce doxycycline absorption. Separate doses of these from doxy-PEP by 2 hours.
Side effects and safety
For event-driven use (not continuous daily dosing), doxy-PEP is generally well-tolerated. Common side effects include:
- Stomach upset, nausea (most common; take with food)
- Esophageal irritation or heartburn (prevented by taking upright with water)
- Photosensitivity (moderately increased sunburn risk; use sunscreen)
- Occasional yeast infections or GI disturbances
Doxycycline should not be used by:
- People allergic to tetracycline-class antibiotics
- Pregnant women and children under 8 (can affect developing bones and teeth)
- People with severe liver disease (discuss with your provider)
Concerns about antimicrobial resistance
The main scientific concern with widespread doxy-PEP use is antimicrobial resistance — the worry that regular doxycycline exposure will select for resistant bacterial strains, making these antibiotics less effective for STIs and other infections over time.
Evidence to date is mixed but mostly reassuring:
- Gonorrhea already has significant tetracycline resistance in many regions, so doxy-PEP doesn't dramatically change that landscape — but it may accelerate it
- Chlamydia and syphilis remain highly susceptible to doxycycline; resistance has not emerged meaningfully
- Concerns about Staphylococcus aureus (unrelated to STIs but relevant to overall antibiotic stewardship) have been raised, but effects appear modest so far
- Resistance surveillance is ongoing — CDC and state health departments are monitoring patterns closely
The current consensus: doxy-PEP's benefit for STI prevention in high-risk populations outweighs resistance concerns, but the protocol should be targeted (not universal) and paired with ongoing surveillance. People taking doxy-PEP should continue regular STI testing and follow clinical guidelines.
How to get doxy-PEP
Telehealth services (fastest)
Online telehealth services like MISTR provide doxy-PEP prescriptions after a brief intake and review by a licensed provider. Since doxycycline is a generic, widely-available antibiotic, a prescription can typically be filled at any pharmacy (CVS, Walgreens, Walmart) for cash or insurance. Many telehealth services can also coordinate $0 access through their 340B partnerships.
Your primary care physician
Any primary care provider can prescribe doxy-PEP. Bring the CDC's 2024 doxy-PEP guidelines to your appointment if your provider isn't familiar with the protocol. Many PCPs serving LGBTQ+ populations are increasingly comfortable prescribing it.
Sexual health clinics
LGBTQ+-focused clinics (Callen-Lorde in NYC, LA LGBT Center, Howard Brown in Chicago, Whitman-Walker in DC, Fenway Health in Boston) routinely offer doxy-PEP prescriptions. Many city sexual health clinics now include doxy-PEP in their standard STI prevention counseling.
FQHCs and Ryan White clinics
Federally Qualified Health Centers and Ryan White clinics offer doxy-PEP on a sliding-scale basis and can coordinate access for uninsured patients.
How much does doxy-PEP cost?
Doxycycline is one of the cheapest prescription antibiotics on the market. Cash pricing without insurance, with a GoodRx or Costco coupon, is typically:
| Supply | Typical cash price |
|---|---|
| 10 tablets (100mg) — about 5 doses | $5–$15 |
| 30 tablets (100mg) — about 15 doses | $10–$30 |
| 60 tablets (100mg) — about 30 doses | $15–$40 |
With insurance, doxy-PEP is typically a tier 1 generic with copays of $0–$15. Telehealth platforms that handle doxy-PEP through 340B partnerships can often provide it at $0 regardless of insurance status.
The consultation cost (through a telehealth platform or in-person provider) is a bigger variable than the drug itself. At most telehealth platforms, the consultation is free. At an in-person provider, it depends on your insurance.
Combine doxy-PEP with PrEP through one platform
Most patients who benefit from doxy-PEP also benefit from PrEP. MISTR coordinates both through a single service — one intake, one provider, $0 medication.
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Doxy-PEP vs other STI prevention strategies
Doxy-PEP is one tool in a broader STI prevention toolkit, not a replacement for others:
| Strategy | What it does |
|---|---|
| Condoms | Prevent bacterial STIs and HIV. Best-in-class for comprehensive protection, but usage is inconsistent in many communities. |
| PrEP (for HIV) | Prevents HIV. Does not prevent bacterial STIs. |
| Regular STI testing | Detects infections early for treatment. Doesn't prevent infection but reduces transmission. |
| Meningococcal vaccine (4CMenB) | Recent evidence suggests partial cross-protection against gonorrhea. CDC is reviewing for wider use. |
| Doxy-PEP | Prevents chlamydia, syphilis, and some gonorrhea after exposure. Doesn't prevent HIV. |
The best approach combines multiple strategies: condoms when possible, PrEP for HIV prevention, regular STI testing, and doxy-PEP as post-exposure bacterial STI prevention for those who qualify. None of these is all-or-nothing — most people benefit from a layered approach.
Frequently asked questions
How much does doxy-PEP cost?
The medication itself is cheap — typically $10–$30 cash for a supply of 30 tablets with a GoodRx coupon. Many insurance plans cover doxy-PEP at $0–$15 as a tier 1 generic. Telehealth platforms that coordinate 340B access can often provide it at $0.
Can I get doxy-PEP online?
Yes. Services like MISTR prescribe doxy-PEP after a brief online intake and provider review. Doxycycline is a generic widely available at all major pharmacies, so filling the prescription is straightforward. Many platforms coordinate $0 access through 340B partnerships.
Is doxy-PEP safe?
For short-term, event-driven use, doxy-PEP has an excellent safety profile. Doxycycline has been widely prescribed for decades. The most common side effects are mild stomach upset and increased sun sensitivity. The main scientific concerns are antimicrobial resistance (discussed above) and long-term microbiome effects, which are being actively studied.
Does doxy-PEP work for cisgender women?
The evidence for cisgender women is mixed. The most rigorous trial in Kenyan cisgender women (dPEP Kenya) didn't show clear benefit. The CDC's current guidelines do not formally endorse doxy-PEP for cisgender women. Some providers offer it off-label; research is ongoing. Discuss with a provider who understands your specific situation.
Can I take doxy-PEP every day?
The standard doxy-PEP protocol is event-driven: 200mg within 72 hours after sex, not more than once per 24 hours. Daily doxycycline prophylaxis (doxyPrEP) is a different approach with its own evidence base and is less commonly used due to higher resistance and side effect concerns. Discuss with your provider if you're considering continuous prophylaxis.
Can I use doxy-PEP with PrEP?
Yes. PrEP (for HIV) and doxy-PEP (for bacterial STIs) are complementary. They prevent different infections and don't interact problematically. Many telehealth platforms prescribe both together as part of a comprehensive sexual health approach.
What if I had sex more than 72 hours ago?
If you're outside the 72-hour doxy-PEP window, the intervention has much less evidence of benefit. Instead, focus on STI testing: chlamydia and gonorrhea can be tested about 1–2 weeks after exposure; syphilis typically tests positive 3–4 weeks post-exposure. Early detection and treatment of confirmed infections is effective even without prophylaxis.
Where can I find the CDC's doxy-PEP guidelines?
The CDC published "Guidelines for the Use of Doxycycline Postexposure Prophylaxis for Bacterial STI Prevention" in June 2024. Search for "CDC doxy-PEP guidelines" on CDC.gov or ask your provider for a copy.
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MISTR prescribes doxy-PEP alongside PrEP, creating a combined bacterial STI + HIV prevention strategy. Both prescriptions, one platform, most patients pay $0. Available in all 50 states.
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