Online Dermatologist > ‘Post-Sex Pill’ for STDs Shows Potential in Reducing Infections

‘Post-Sex Pill’ for STDs Shows Potential in Reducing Infections

by | Oct 3, 2023 | Blog, Sexual Health, STD, STD Treatment

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Sexually transmitted infections (STI) are one of the most common infectious diseases worldwide. The Sexually Transmitted Disease Surveillance 2021 conducted by Centers for disease control (CDC) provides evidence of an increase in several STIs including chlamydia, gonorrhea, and syphilis in the US.1 It shows that in 2021, there were over 2.5 million newly reported cases of chlamydia, gonorrhea, and syphilis combined. Despite the existing preventive methods such as using condoms during sexual intercourse, regular screening, vaccination and treatment, there is a high number of STIs reported each year. These diseases can give rise to serious complications, including infertility, cancer, and death. Therefore, STIs are a major ongoing problem in the current society that needs a better solution.

“Post-sex pill for STI” brings a promising solution to this enormous public health issue. A recent study done by the University of California, San Francisco (UCSF) and University of Washington shows the potential of using the medication ‘Doxycycline’ to reduce the risk of bacterial sexually transmitted infections from person to person.2 Doxycycline is an antibiotic of the tetracycline group, that can kill the bacteria which cause gonorrhea and chlamydia, when taken within 72 hours of condomless sex. It comes in the form of a 200mg single dose tablet that you can swallow after sexual intercourse. It is just like the morning after pill that is widely used to prevent unwanted pregnancies, except here it prevents the transmission of STIs.


Past attempts to utilize Doxycycline

There have been several studies done to assess the efficacy of various pre-exposure and post exposure medication to prevent STIs in the past as well. The use of doxycycline postexposure prophylaxis was linked with a 47% decrease in the incidence of sexually transmitted infections in the IPERGAY (Intervention Préventive de l’Exposition aux Risques avec et pour les Gays) study.3 G. La Rouche et al observed an approximate 70% decrease in the prevalence of syphilis and chlamydia, but no reduction was observed in the occurrence of gonorrhea with Doxycycline prophylaxis.4


Study method

A total number of 501 people, consisting of men who have sex with men (MSM) and transgender women from Seatle and San Francisco were chosen for the study. They all had a history of STIs, and were either living with HIV or taking pre-exposure prophylaxis for HIV. They were divided into two groups and one was provided with Doxy-PEP, (Doxycycline post-exposure tablet) to be taken ideally within 24 hours, and no later than 72 hours from each unprotected sexual activity. The other group was given standard care without Doxy-PEP. This was done so that multiple aspects such as drug safety, biologic effects of the drug, side effects, adherence to the drug, antimicrobial resistance and potential change in the sexual behavior of the participants can be monitored and compared.

Participants had quarterly visits for a period of one year, with additional visits schedules as needed. The evaluation of drug safety was conducted using the Division of AIDS (DAIDS) system for reporting adverse events.5 Different methods were used to check the bacterial levels in the bodies of the participants. Pharyngeal, rectal and urine samples were taken to look for the presence of bacteria that cause gonorrhea and chlamydia with a technique called nucleotide amplification. Blood samples were collected to conduct syphilis serologic studies in accordance with the Centers for Disease Control and Prevention (CDC) guidelines for diagnosing the disease.6 During the doxycycline treatment, the participants had their complete blood counts and liver-enzyme levels measured at 3 and 9 months. Doxycycline resistance was also assessed by measuring the levels of the bacteria called Staphylococcus aureus.


The research indicated that individuals who took the pill had significantly reduced the risk of contracting STIs: chlamydia by about 90%, syphilis by approximately 80%, and gonorrhea by more than 50% when compared to those who did not take the pill after unprotected sexual activity. Overall, individuals who took doxycycline had a much lower likelihood of being diagnosed with a STI or HIV compared to the control group. The difference was about two-thirds, with only 10.7% of patients on doxycycline prophylaxis being diagnosed with an STI, and 11.8% with HIV.

Out of the 3 diseases assessed, Gonorrhea was the most frequently seen STI in both study and control groups. Still, the people who took Doxycycline showed less cases of Gonorrhea compared to the control group with no prophylaxis, proving the efficacy of the drug even against Gonorrhea.

The side effects reported were mild, which consisted of few cases of transaminitis, diarrhea and headache. 89% people who took the medication had a favorable opinion towards the drug.


Implications and challenges of the pill for STI prevention

This pill provides an easy and convenient method to prevent STIs for an affordable price. It is widely available and safe to use with only minimum side effects and minimal drug interactions with other medications. Therefore, this pill can reduce the STI burden and their complications, uplifting individual the public health status without causing considerable harm. This is especially important for areas with low facilities for regular screening, vaccination or treatment.

One major challenge of Doxycycline pill is the inadequate data on long term complications. For example, long term use of antibiotics is known to alter the bacteria present in your body, sometimes making them resistant to the antibiotics given, so that killing them is not easy.7 Also, there are the social factors to be considered, such as stigma and continued compliance to the medication.

Also, there are several unanswered questions that heighten the requirement of more research. Optimal dosage and timing of doxycycline treatment, the efficacy of this medication against other non-bacterial transmitted STIs such as HIV, time duration the protective effect of the pill lasts and the long-term effects of it on health and fertility of the users are some examples.


Key takeaways

Doxycycline post-sex tablet is a pill that can reduce transmission of STIs when taken ideally within 24 hours from unprotected sexual activity. This pill is a safe and effective way to reduce the STI burden and their complications. New England Journal of Medicine published a study with promising results, with an overall STI reduction by two thirds among people who took the doxycycline prophylaxis tablet, compared to the group that underwent standard treatment without prophylaxis. More research is needed to assess long term outcomes and other challenges this intervention brings.

Prevention before treatment: Doxycycline post-exposure prophylaxis brings us one step closer to safer sex and healthy life.


U.S. Health Officials Plan to Endorse – Antibiotic Doxycycline Hyclate as a Morning-After Pill Against STDs

Building upon the promising findings from the studies discussed earlier in this article, U.S. health officials have now taken a substantial step toward endorsing doxycycline hyclate as a morning-after pill for reducing the risk of STDs. The proposed guideline from the Centers for Disease Control and Prevention (CDC) is backed by four studies exploring the effectiveness of doxycycline against bacterial STDs. This guideline is primarily aimed at gay and bisexual men, as well as transgender women, who have had an STD in the previous 12 months and are at high risk for re-infection.

This endorsement highlights the practical application and broader acceptance of doxycycline, reinforcing the results of the earlier mentioned studies that demonstrated the antibiotic’s efficacy in significantly reducing the incidence of chlamydia, syphilis, and gonorrhea when taken post-sex. The CDC’s guideline was informed by a collection of studies, including a notable one published in the New England Journal of Medicine, which aligns with the research findings shared in this article regarding doxycycline’s potential in STD prevention.

In line with the results discussed here, the CDC’s endorsement also emphasizes the significant protective effects of doxycycline, including about a 90% reduction in chlamydia infections, about an 80% reduction in syphilis, and more than a 50% reduction in gonorrhea for individuals who took the antibiotic post-sex.

The endorsement comes at a critical time when STD rates are soaring to record levels, echoing the urgent call for more preventive measures highlighted in this article. The proactive steps taken by health departments in San Francisco and other regions on the West Coast are now gaining broader acknowledgment and support from national health officials.

This endorsement not only validates the encouraging data on doxycycline’s preventive potential against STDs but also paves the way for more widespread adoption and discussion of this preventive measure among healthcare providers and individuals at higher risk for STDs.

The concerns regarding antibiotic resistance and the specific side effects of doxycycline, such as stomach problems and sun-induced rashes, remain pertinent. However, the endorsement by U.S. health officials underscores the growing consensus within the medical community regarding the benefits and practical utility of doxycycline as a post-sex prophylactic measure against STDs.



  1. Sexually Transmitted Disease Surveillance, 2021. (n.d.). Retrieved May 11, 2023, from
  2. Luetkemeyer, A. F., Donnell, D., Dombrowski, J. C., Cohen, S., Grabow, C., Brown, C. E., Malinski, C., Perkins, R., Nasser, M., Lopez, C., Vittinghoff, E., Buchbinder, S. P., Scott, H., Charlebois, E. D., Havlir, D. v, Soge, O. O., Celum, C., & DoxyPEP Study Team. (2023). Postexposure Doxycycline to Prevent Bacterial Sexually Transmitted Infections. The New England Journal of Medicine, 388(14), 1296–1306.
  3. Molina, J. M., Charreau, I., Chidiac, C., Pialoux, G., Cua, E., Delaugerre, C., Capitant, C., Rojas-Castro, D., Fonsart, J., Bercot, B., Bébéar, C., Cotte, L., Robineau, O., Raffi, F., Charbonneau, P., Aslan, A., Chas, J., Niedbalski, L., Spire, B., … Lorente, N. (2018). Post-exposure prophylaxis with doxycycline to prevent sexually transmitted infections in men who have sex with men: an open-label randomised substudy of the ANRS IPERGAY trial. The Lancet. Infectious Diseases, 18(3), 308–317.
  4. la Ruche, G., Goubard, A., Berçot, B., Cambau, E., Semaille, C., & Sednaoui, P. (2014). Gonococcal infections and emergence of gonococcal decreased susceptibility to cephalosporins in France, 2001 to 2012. Euro Surveillance : Bulletin Europeen Sur Les Maladies Transmissibles = European Communicable Disease Bulletin, 19(34).
  5. National Institutes of Health. DAIDS adverse event grading tables. February 1, 2018 ( -research-sites/daids-adverse-event-grading -tables).
  6. Workowski, K. A., Bachmann, L. H., Chan, P. A., Johnston, C. M., Muzny, C. A., Park, I., Reno, H., Zenilman, J. M., & Bolan, G. A. (2021). Sexually Transmitted Infections Treatment Guidelines, 2021. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports, 70(4), 1–187.
  7. Jo, J. H., Harkins, C. P., Schwardt, N. H., Portillo, J. A., Zimmerman, M. D., Carter, C. L., Hossen, M. A., Peer, C. J., Polley, E. C., Dartois, V., Figg, W. D., Moutsopoulos, N. M., Segre, J. A., & Kong, H. H. (2021). Alterations of human skin microbiome and expansion of antimicrobial resistance after systemic antibiotics. Science Translational Medicine, 13(625).
  8. Patel RS, Parmar M. Doxycycline Hyclate. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. Updated May 22, 2023. Accessed October 4, 2023.
  9. Centers for Disease Control and Prevention. Guidelines for the Use of Doxycycline Post-Exposure Prophylaxis for Bacterial Sexually Transmitted Infection (STI) Prevention. Published October 2, 2023. Accessed October 4, 2023.


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