What is Doxy-PEP? A doctor explains the STD prevention pill taken within 72 hours of sex.
目次
June 8, 2026
What is Doxy-PEP? A Doctor Explains This STD Prevention Medication Taken Within 72 Hours of Sex
For the prevention of chlamydia, syphilis, and gonorrhea
Many people have anxieties and questions like, "I had sex without a condom," "I'm worried about STIs (sexually transmitted infections), but can I only do something after I'm infected?" or "I heard about a drug called Doxy-PEP, but I don't know what it is."
Doxy-PEP (Doxycycline Post-Exposure Prophylaxis) is a preventive medication that can significantly reduce the risk of chlamydia, syphilis, and gonorrhea infection when taken within 72 hours of risky sexual intercourse. In 2024, the CDC (U.S. Centers for Disease Control and Prevention) included it in its guidelines, and it is rapidly gaining attention in Japan.
In this article, a doctor from Mona Aoyama Clinic will provide a clear explanation, based on medical evidence, of what Doxy-PEP is, its effects, how to take it, side effects, cost, and how to get it prescribed online.
- Prescription available from the same day. Online consultation available nationwide.
- Consultation, prescription, and delivery completed via LINE or online.
- Consultation also available for combination with PrEP/PEP.
- Regular HIV/STD testing can also be done at the same time.
👉 If you wish to receive a Doxy-PEP prescription, please consult us here.
What is Doxy-PEP?
Doxy-PEP is a method of preventing sexually transmitted infections by taking the antibiotic "doxycycline" once within 72 hours after sexual intercourse. It is officially called "Doxycycline Post-Exposure Prophylaxis."
| Item | Content |
|---|---|
| Type of drug | Antibiotic (tetracycline class) |
| Active ingredient | Doxycycline 100mg × 2 tablets = 200mg |
| Timing of administration | As soon as possible, and within a maximum of 72 hours, after risky sexual intercourse |
| STIs that can be prevented | Chlamydia, Syphilis (Treponema pallidum), Gonorrhea (Neisseria gonorrhoeae) |
| Approximate preventive efficacy | Chlamydia: approx. 70-90%, Syphilis: approx. 70-80%, Gonorrhea: approx. 50-60% |
| Target audience | Primarily MSM (men who have sex with men), transgender women (TGW) |
| CDC guidelines | Recommended in 2024 (supports prescription for specific risk groups) |
⚠️ Doxy-PEP is not a "treatment for infection," but a "preventive medication" for infection. If symptoms suggesting infection are already present, separate STI testing and treatment are required.
STIs Doxy-PEP can and cannot prevent
Doxy-PEP does not prevent all sexually transmitted infections. It is important to accurately understand what it can and cannot prevent.
| STI | Doxy-PEP effect | Approximate prevention rate |
|---|---|---|
| Chlamydia | ✅ High preventive effect | approx. 70-90% |
| Syphilis | ✅ High preventive effect | approx. 70-80% |
| Gonorrhea (Gonococcal infection) | ⚠️ Some effect (however, resistant strains are increasing, so the preventive effect is limited) | approx. 50-60% |
| HIV | ❌ No preventive effect (PEP/PrEP required) | — |
| Herpes (HSV) | ❌ No preventive effect | — |
| Hepatitis B/C | ❌ No preventive effect (vaccine/other measures required) | — |
| HPV (Human papillomavirus) | ❌ No preventive effect (vaccine is effective) | — |
⚠️ If you are concerned about HIV infection, PEP (HIV Post-Exposure Prophylaxis) is needed, not Doxy-PEP. PEP also needs to be started within 72 hours. If you are concerned about both HIV and other STIs, Doxy-PEP and PEP can be combined. Our clinic supports prescriptions for both.
How and when to take Doxy-PEP
The timing of Doxy-PEP administration greatly influences its effectiveness. It's crucial to understand the correct way to use it.
| Item | Content |
|---|---|
| Dosage | One single dose of Doxycycline 200mg (2 tablets of 100mg) |
| Timing | As soon as possible, and within a maximum of 72 hours (3 days), after risky sexual intercourse |
| Frequency of administration | One dose per sexual act. If there are multiple acts, take at least 30 hours after the previous dose. |
| Relation to meals | Taking with food can reduce stomach irritation. |
| Water intake | Drink with 1-2 glasses of water (to prevent adhesion to the esophagus). |
| Precautions after administration | Do not lie down for 30 minutes after taking (to prevent esophagitis). |
| Photosensitivity | Avoid direct sunlight and UV radiation during administration (risk of photosensitivity). |
⏱️ "Within 72 hours" is crucial. The longer the time after sexual intercourse, the lower the preventive effect. If you have had risky sexual intercourse, start taking the medication as soon as possible. Our online clinic offers same-day prescription and same-day shipping.
Side Effects of Doxy-PEP
Doxycycline is an antibiotic that has been used for many years and is generally considered safe. However, the following side effects have been reported:
| Side effect | Frequency | Management |
|---|---|---|
| Gastrointestinal symptoms (nausea, stomach discomfort, diarrhea) | Relatively common | Reduced by taking with food |
| Photosensitivity (skin reddening when exposed to sunlight) | Rare | Avoid direct sunlight/UV exposure during administration |
| Esophagitis (inflammation due to adhesion to the esophagus) | Rare | Take with plenty of water, do not lie down after administration |
| Candida (vaginal/oral) | Rare | Due to changes in gut/vaginal flora. Consult if symptoms appear. |
| Allergic reaction | Very rare | If rash/hives appear, stop taking immediately and seek medical attention. |
Regarding the concern of antibiotic resistance with regular use, the risk can be minimized by combining appropriate usage with regular STI testing. For more details, please refer to "Doxy-PEP and Antibiotic Resistance – Understanding for Safe Use."
Who should and should not use Doxy-PEP
| Category | Who it applies to |
|---|---|
| People who can consider using it | ・Have been infected with syphilis, chlamydia, or gonorrhea in the past 12 months ・Have had unprotected sexual intercourse (especially MSM/TGW) ・Have sexual intercourse with multiple partners ・Are using PrEP but are concerned about other STIs |
| People who cannot use it or need to be cautious | ・Pregnant or potentially pregnant individuals (risk to fetus) ・Individuals with an allergy to tetracycline antibiotics ・Children under 8 years old (risk of tooth discoloration) ・Individuals with severe liver dysfunction ・Individuals concurrently using certain medications (e.g., warfarin, antacids) *Consultation required |
Important Regular Testing While Using Doxy-PEP
Doxy-PEP does not 100% prevent infection. Even with use, regular STI testing every 1 to 3 months is recommended.
- Regular testing allows for early detection of infection.
- Allows for early detection of resistant strains.
- Confirms that Doxy-PEP is working properly.
- Contributes to early detection of other sexually transmitted infections (HIV, hepatitis B, etc.).
At our clinic, we offer online and mail-order regular STI testing in conjunction with Doxy-PEP prescriptions.
Differences between Doxy-PEP, PrEP, and PEP
There are multiple options for STI/HIV prevention medications. It is important to understand the role of each.
| Type of drug | Purpose | Timing of administration | Target infections |
|---|---|---|---|
| Doxy-PEP | STI prevention (post-exposure) | Within 72 hours of sexual intercourse | Chlamydia, Syphilis, Gonorrhea |
| PEP | HIV prevention (post-exposure) | Within 72 hours of sexual intercourse, continued for 28 days | HIV |
| PrEP | HIV prevention (pre-exposure) | Daily continuous administration before sexual intercourse | HIV |
If you are concerned about both HIV and STIs, simultaneous prescription of Doxy-PEP + PEP is possible. Our clinic offers prescriptions for each or in combination.
Frequently Asked Questions
A doctor's consultation is required for prescription. There are cases where it cannot be used, such as for pregnant individuals or those with an allergy to tetracycline antibiotics. If you complete the medical questionnaire through an online consultation, same-day prescription is possible.
The standard is to take it within 72 hours (3 days) after sexual intercourse. The earlier it is taken, the higher the effectiveness, so if you have had risky sexual intercourse, take it as soon as possible. Preventive effects cannot be expected after 72 hours.
Condoms are the most effective means of preventing STIs, but the risk is not zero due to slipping, tearing, or forgetting to remove them during use. Combining Doxy-PEP with condoms can provide higher preventive effects. If you have had unprotected sexual intercourse and are concerned, consider taking Doxy-PEP.
The impact of regular use on antibiotic resistance is an ongoing area of research. Since using it when already infected carries a higher risk of developing antibiotic resistance, our clinic recommends STI testing before prescription. Appropriate use combined with regular testing is crucial.
Yes. Our clinic offers fully online consultation, prescription, and medication delivery. Same-day prescription is possible via LINE or online medical questionnaire, and if payment is completed by 4 PM, we will ship the same day.
No significant interaction with alcohol has been reported, but it may increase the likelihood of gastrointestinal symptoms. It is recommended to take it with or after a meal if possible.
Current CDC guidelines primarily target MSM and transgender women, and research on recommendations for cisgender women is limited. Additionally, it cannot be used by pregnant or lactating individuals. Please consult your doctor about your specific situation.
Yes, it is necessary. Doxy-PEP does not 100% prevent infection, and there are STIs it cannot prevent, such as HIV and herpes. Regular testing every 1 to 3 months is recommended. Our clinic also offers mail-in test kits.
Flow of Prescription at Our Clinic (Online Consultation)
- Book an online consultation or visit on the same day Fill out a medical questionnaire via LINE or web. Reservations are not required.
- Fill out the medical questionnaire Please include the time elapsed since sexual intercourse, your medical history, allergies, current symptoms, and any other medications you are taking.
- Online consultation with a doctor The doctor will review the contents of the medical questionnaire. They will determine if Doxy-PEP is appropriate for you.
- Prescription and medication guidance If a prescription is decided, we will provide information on the necessary dosage and usage. If you wish for regular use, a bulk prescription is also possible.
- Payment and Shipping Payment completed by 4 PM will be shipped the same day. Late-night immediate delivery options (10 PM to 9 AM) are also available.
- Home care and guidance for regular follow-ups We will explain how to take the medication and precautions. We will also advise on the timing of regular tests.
Fees
| Plan | Price (incl. tax) | Content |
|---|---|---|
| Doxy-PEP 3 doses | ¥7,500/month (subscription) | 100mg × 6 tablets. Monthly subscription plan |
| Doxy-PEP 5 doses | ¥10,000/month (subscription) | 100mg × 10 tablets. Monthly subscription plan |
| Doxy-PEP 10 doses | ¥14,000 | 100mg × 20 tablets |
| Doxy-PEP 20 doses | ¥24,000 | 100mg × 40 tablets |
| Doxy-PEP 30 doses | ¥30,000 | 100mg × 60 tablets |
| Late-night immediate delivery option | ¥10,000 | Delivery between 10 PM and 9 AM. For emergencies. |
※ Prices are subject to change. Please check the shop page for the latest information.
Related Columns
Doxy-PEP's Effectiveness: Prevention Rates and Limitations for Syphilis, Chlamydia, and Gonorrhea How to Take Doxy-PEP: Timing, Dosage – A Complete Guide for Correct Use Doxy-PEP Side Effects and Precautions | What You Need to Know for Safe Continued Use Doxy-PEP and Antibiotic Resistance – Understanding for Safe Use Differences between Doxy-PEP, PrEP, and PEP? A Comparative Explanation of HIV and STI Prevention MedicationsClinic Hours and Access
| Clinic Name | Mona Aoyama Clinic |
| Consultation Format | Online Consultation (nationwide) / In-person Consultation (Tokyo, Aoyama) |
| Location | D Building 3F, 1-10-3 Minami-Aoyama, Minato-ku, Tokyo 107-0062 |
| Nearest Station | 5-minute walk from "Aoyama-itchome Station" on the Tokyo Metro Ginza Line and Hanzomon Line |
| Online Consultation | 24-hour reception, same-day shipping available (for payments made by 4 PM) |
| Official LINE | Medical questionnaire, consultation, and prescription requests possible via LINE |
For Doxy-PEP prescriptions, contact Mona Aoyama Clinic
Online consultation available nationwide. Same-day prescription and same-day shipping (for payments by 4 PM). Feel free to contact us via LINE.