What is DoxyPEP?

Published on Nov 14, 2023 | 2:19 PM

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Every year, it's estimated that around 374 million people are infected with curable sexually transmitted infections, most notably syphilis, gonorrhea, and chlamydia. (1) Just in the United States alone, the number of annual infections concerning the same STIs hovers between 1.5 million and just below 2 million. (2) Such rising numbers, alongside concerns for antibiotic resistance STDs, have driven the scientific and healthcare communities towards advancing new methods of cures and spread prevention. That’s where the recent development of DoxyPEP has made such an impact on doctors and patients alike. 

Designed to function similarly to a morning-after pill, DoxyPEP is an oral antibiotic that has proven effective against immediate exposure to bacterial sexually transmitted diseases. Most effective if taken within 24 hours of exposure, DoxyPEP is also known to reduce bacterial STDs if taken within 72 hours.  

Is DoxyPEP the same as doxycycline?

A shortened version of Doxycycline Post Exposure Prophylaxis, DoxyPEP is a single dose of the antibiotic doxycycline. Put another way, the long version means a dose of doxycycline after exposure or unprotected sex. The name in itself is the antibiotic and how to take it. (3)

What does DoxyPEP protect against?

As an antibiotic, DoxyPEP is most effective against bacterial sexually transmitted diseases. (3) More specifically, the medication has proven effective against: 

Gonorrhea: Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. It primarily affects the genital and reproductive tract but can also occur in the throat, eyes, and rectum. Common symptoms in men include painful urination, discharge from the penis, and testicular pain, while women may experience vaginal discharge, pelvic pain, and painful urination. However, it's important to note that many infected individuals, especially women, may not display noticeable symptoms. If left untreated, gonorrhea can lead to severe complications such as pelvic inflammatory disease, infertility, and an increased risk of HIV transmission. 

Chlamydia: Chlamydia is a common sexually transmitted infection caused by the bacterium Chlamydia trachomatis. It can affect both men and women and is often asymptomatic.  When symptoms do occur, they can include pain or a burning sensation during urination, genital discharge, and abdominal pain. In women, untreated chlamydia can lead to serious complications such as pelvic inflammatory disease, which may result in infertility or ectopic pregnancy. In men, it can cause inflammation of the urethra and, in rare cases, lead to infertility. 

Syphilis: Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. The disease progresses through stages, each with distinct symptoms. In the primary stage, a painless sore or ulcer, known as a chancre, develops at the site of infection, often on the genitals, anus, or mouth. If left untreated, syphilis progresses to the secondary stage, characterized by skin rashes, mucous membrane lesions, and flu-like symptoms. The infection can then enter a latent stage, during which no symptoms are evident, but the bacteria remain in the body. Without treatment, syphilis can advance to the tertiary stage, potentially causing severe damage to organs such as the heart, brain, and nerves, leading to serious health complications. 

What does DoxyPEP not treat? 

At the time of writing, DoxyPEP is known to be effective in the treatment of bacterial STDs like gonorrhea, chlamydia, and syphilis. It does not treat viral or parasitic STDs, including: 

  • Herpes: Herpes is a viral infection caused by the herpes simplex virus (HSV), primarily HSV-1 and HSV-2. It manifests as painful sores or blisters on the mouth or genitals. Unlike bacterial infections, herpes is not susceptible to antibiotics because antibiotics target bacteria, not viruses. Antiviral medications, such as acyclovir, valacyclovir, and famciclovir, are commonly used to manage herpes outbreaks by suppressing viral replication and alleviating symptoms, but they do not eliminate the virus from the body. Herpes infections can persist for life, with the virus remaining dormant and periodically reactivating, leading to recurrent outbreaks.
  • Human Immunodeficiency Virus (HIV): HIV is a retrovirus that attacks the immune system, specifically CD4 cells (T cells), weakening the body's ability to fight off infections and diseases. Unlike bacterial infections, HIV is not susceptible to antibiotics because antibiotics target bacteria, not viruses. Antiretroviral drugs are the mainstay of HIV treatment, working to inhibit the virus's replication and slow the progression of the disease. These medications help control the virus but do not cure HIV, and lifelong adherence to antiretroviral therapy is essential for managing the infection and maintaining immune function.
  • Trichomoniasis: Trichomoniasis is a sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis. Unlike bacteria, which antibiotics can treat, trichomoniasis is a parasitic infection, and standard antibiotics may not be effective. The recommended treatment for trichomoniasis is usually the antiparasitic medication metronidazole or tinidazole. These drugs work by disrupting the DNA of the parasite, leading to its death. 

Why is doxycycline so powerful?

Doxycycline is considered a powerful antibiotic due to its broad-spectrum activity against a wide range of bacteria, including both Gram-positive and Gram-negative bacteria, as well as certain parasites and atypical microorganisms. It belongs to the tetracycline class of antibiotics and works by inhibiting bacterial protein synthesis. Additionally, doxycycline is often effective against bacteria that have developed resistance to other classes of antibiotics. Its versatility, oral administration, and ability to penetrate tissues make doxycycline a valuable and widely used antibiotic for treating various bacterial infections, including respiratory, urinary tract, skin, and sexually transmitted infections. (4)

How effective is DoxyPEP?

At the time of writing, DoxyPEP lowers the chance of catching chlamydia, syphilis, and gonorrhea by two-thirds when taken immediately after exposure through unprotected sex. (5) Alongside the ease of use and the lack of heavy side effects, DoxyPEP has proven exceedingly effective for those who use it immediately after exposure. 

How do you take doxycycline for STDs?

DoxyPEP is taken orally, with there being two doses per three days. Ideally, the first dose should be taken within 24 hours after exposure or unprotected sex and the second the next day or day after. Under no circumstances should two doses be taken within the same day or 24-hour window. 

What should I avoid while taking doxycycline?

Birth control has been reported to be less effective when taken around the same time as doxycycline. Additionally, antacids and certain supplements are known to decrease the effectiveness of the antibiotic. (6) These supplements include: 

  • Calcium
  • iron 
  • Magnesium
  • Zinc
  • Sodium Bicarbonate

In the case of such minerals and antacids, it's recommended to separate the taking of either with at least two hours. Additionally, there are some foods that should be avoided when taking doxycycline or DoxyPEP, including: 

  • Milk 
  • Butter 
  • Cheese 
  • Eggs 
  • Kale
  • Spinach

If any of these need to be consumed, it is best to do so at minimum two hours before or four hours after taking doxycycline. (6) Additionally, alcohol should be avoided entirely when taking DoxyPEP or doxycycline, as it can reduce the effectiveness of the antibiotic. 

Get DoxyPEP through CallonDoc today!

Alongside our testing and treatment of common sexually transmitted diseases, CallonDoc offers DoxyPEP for those looking to get immediate treatment for STD exposure. With one in five Americans on average having an STD, the risk of developing an STD after condomless intercourse is high. Call-On-Doc recommends safe sex practices but can help lower your risk of and treat STDs with DoxyPEP online today if you have had or are unsure of STD exposure.


  1. “Sexually transmitted infections (STIs).” World Health Organization (WHO), 10 July 2023, https://www.who.int/news-room/fact-sheets/detail/sexually-transmitted-infections-(stis).
  2. “Sexually Transmitted Disease Surveillance, 2021.” CDC, https://www.cdc.gov/nchs/covid19/index.htm.
  3. “DoxyPEP for STI Prevention.” LA County Public Health, 5 5 2023, http://publichealth.lacounty.gov/dhsp/DPHSexualHealthClinics/HealthEducationLibrary/DoxyPEP/DoxyPEP_Factsheet-EN_FINAL_05.05.2023.pdf.
  4. Patel, Reema S., and Mayur Parmar. “Doxycycline Hyclate - StatPearls.” NCBI, 22 May 2023, https://www.ncbi.nlm.nih.gov/books/NBK555888/.
  5. Luetkemeyer, Anne F., et al. “Postexposure Doxycycline to Prevent Bacterial Sexually Transmitted Infections.” NEJM, The New England Journal of Medicine, 06 04 2023, https://www.nejm.org/doi/full/10.1056/NEJMoa2211934.
  6. “What is Doxycycline?” Poison Control, https://www.poison.org/articles/what-is-doxycycline.

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Wayne C. Hahne,

English graduate and Call-On-Doc’s medical resource guide, Wayne C. Hahne is an experienced and passionate medical education content expert. Through diligent research, provider interviews and utilizing the industry's leading resources for wellness information, it is Mr. Hahne’s personal mission to educate the general public on medical conditions with in-depth and easy-to-understand written guides.

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