Medically reviewed on October 12, 2023 by Morgan Spicer, Medical Communications Manager. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
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Doxycycline is an antibiotic medication that is used to manage and treat many different infections.  Doxycycline has been used for acne, malaria, skin infections, inflammation, Lyme disease, and often for sexually transmitted infections (STIs) like chlamydia, syphilis, gonorrhea, and pelvic inflammatory disease (PID), a complication that can develop from an STI. 
Doxycycline is typically prescribed to those who have already tested positive for an infection. Doxycycline is often given in the form of an oral tablet or capsule, however intravenous (IV) delivery is possible if necessary.  When treating most STIs, the World Health Organization (WHO) recommends taking 100 mg orally twice a day for seven days.  Because of the growing number of STIs in the United States, some healthcare providers are finding new ways to prescribe doxycycline to high-risk patients. 
Post-exposure prophylaxis (PEP) is a form of treatment that is given after exposure to a potential pathogen in hopes of preventing the infection from occurring.  PEP is frequently associated with HIV prevention, but new research is also focused on the use of doxycycline PEP, or doxyPEP, in order to prevent bacterial infections. [3-4] A study focused on the post-exposure approach found that prescribing doxycycline within 72 hours of unprotected sex helped to lower the combined incidence of multiple bacterial STIs by nearly 67% when compared to standard care.  Current research is highly focused on men who have sex with men (MSM) and transgender women, as these groups are disproportionately impacted by rising STI cases. A study of 400 cisgender women reported that the use of doxyPEP didn’t show much of a difference in bacterial STI incidence when compared to the control group.  More research surrounding the use of doxyPEP in other groups, such as cisgender women, transgender men, and other people assigned female at birth (AFAB) is still needed. While studies have shown promising results, formal clinical guidelines are still lacking. The CDC has put together some considerations for providers and individuals interested in doxyPEP, and some local health departments have already begun prescribing and recommending doxycycline as a post-exposure prevention option.  Most recently, the CDC has proposed guidelines to provide updated clinical guidance for healthcare providers. These proposed guidelines only apply to men who have sex with men and transgender women.  Interested persons are able to provide comments and feedback on these guidelines until November 16 2023.  The ability to hear from the public and providers allows the CDC to gather important input before any formal guidance is finalized. 
Doxycycline requires a prescription, so you’ll need to speak to a healthcare provider if you’re interested in doxyPEP. While there is promising evidence that doxyPEP is effective for certain groups, there isn’t currently any official clinical guidance for healthcare providers to follow.  Because some providers and local health departments have begun prescribing and recommending doxyPEP, the CDC has put together some considerations for the off-label use of doxycycline.  Off-label use refers to a provider prescribing an FDA-approved drug for unapproved use to treat a disease or condition.  The CDC strongly recommends that anyone offering Doxycyline PEP do so alongside risk reduction counseling. This includes comprehensive education on reducing the spread of sexually transmitted infections, STI screening and treatment, recommended vaccinations, linkage to HIV prevention or care, and other services where appropriate.  Keep in mind that most studies have only applied to gay and bisexual men and transgender women. If you do not fall into one of these demographics, your healthcare provider may not be comfortable prescribing you doxycycline for PEP. As more information is gathered and governing organizations update any recommended guidelines, we at Everlywell will continue to provide up-to-date information and services.
According to the CDC’s considerations, doxyPEP should be administered as a 200 mg dose within 72 hours of condomless sex, as was followed in the 2022 study. [5,7] The CDC recommends against using any other dose or antibiotic for PEP. 
So why are some healthcare providers prescribing medication before a confirmed infection? While it may sound strange, this method of prevention isn’t new. Prescribing medications after exposure to a potential pathogen but before an infection takes place is also used to prevent HIV, hepatitis B, rabies, Lyme disease, and many other infections. [9-11] In some ways, taking doxyPEP or other types of post-exposure precautions can be compared to getting a vaccine. We get vaccinated in order to prevent infections or complications from various diseases, just like those taking PEP, PrEP, doxyPEP, etc. do to prevent HIV and other infections. [12-13] Preventing an infection from occurring in the first place can decrease someone’s risk of transmitting the infection to others and developing complications from an untreated infection.  While doxycycline can be administered after an infection has developed, some STIs may not cause symptoms, which can result in the spread of an untreated infection rather easily.  When left untreated, STIs also have the potential to cause lifelong complications such as infertility, organ damage, PID, chronic pelvic pain, and others.  The bottom line is the number of STI cases in the United States is continuing to rise, and other prevention methods don’t seem to be reducing the numbers.  Giving patients a prescription that can actually stop an infection from occurring is a new option that has been proven effective in certain high-risk groups. 
While there are some potential benefits to using doxycycline as a post-exposure medication, there are some negatives to consider. For one, many safe medications can still cause negative side effects.  If someone was not exposed to a bacterial STI but was still prescribed doxycycline, taking an antibiotic may actually do more harm than good. Additionally, prescribing antibiotics to someone who doesn’t need them can lead to antimicrobial-resistant infections. 
Doxycycline is considered a safe medication, but there is a potential for adverse effects. Some common reactions include :
Severe adverse effects are rare but possible. Examples include :
This isn’t an exhaustive list and other side effects may arise from doxycycline use. If you’re concerned about any side effects or have questions about taking doxycycline, reach out to your healthcare provider.
As previously mentioned, the overuse or misuse of antibiotics can actually lead to antimicrobial (antibiotic) resistant infections. [15-16] Antibiotic resistance happens when certain bacteria and fungi evolve enough to defeat antibiotics. We have already witnessed a slight increase in antimicrobial-resistant gonorrhea in one doxyPEP study.  Researchers concluded that more research and longer follow-up periods are needed to better understand the potential antibiotic resistance effect of intermittent doxyPEP use.
At Everlywell, we believe everyone has the right to healthcare, which is why we’re proud to offer a healthcare and wellness suite that includes supplements, at-home health tests, and virtual care visits. If you’re in need of STD testing or would like to speak to a healthcare provider about any symptoms you’re experiencing, shop our selection of at-home STD tests or make an online appointment with a licensed provider. Everlywell products and services are personalized, easy to understand, and evidence-backed.