Doxycycline for Sexually Transmitted Infections

Overseen By Colleen Kelley, MD, MPH

Age: 18 - 65

Sex: Any

Trial Phase: Phase 4

Sponsor: Emory University

Must not be taking: Immunomodulators, Steroids, Chemotherapy, others

Disqualifiers: Liver disease, Allergic reaction, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Prior Safety Data This treatment has passed at least one previous human trial

Approved in 5 Jurisdictions This treatment is already approved in other countries

Compensation: Varies

Number of Visits: 3

Duration: 1 week

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial examines how doxycycline, an antibiotic, behaves in the body after daily use for a week. The study focuses on individuals assigned male or female sex at birth and aims to gather data that could help protect against bacterial sexually transmitted infections (STIs) in the future. Participants will take doxycycline for seven days. The trial may suit those in good health, not currently taking similar antibiotics, and willing to use condoms during the study. Participants must be comfortable providing samples like blood and urine and undergoing a few medical procedures. As a Phase 4 trial, this research seeks to understand how this already FDA-approved and effective treatment benefits more patients.

Will I have to stop taking my current medications?

The trial requires that you do not take doxycycline or other tetracycline-derived antibiotics during the study. Additionally, you cannot use certain medications like systemic immunomodulatory agents, high doses of steroids, chemotherapy, or experimental drugs within 90 days before joining the study.

What is the safety track record for doxycycline?

Research shows that doxycycline is generally safe for use. Studies have found that taking 200 mg of doxycycline within 72 hours after sex can lower the risk of infections like syphilis and chlamydia by over 70%. The Centers for Disease Control and Prevention (CDC) suggests using doxycycline to prevent bacterial sexually transmitted infections (STIs) in people at high risk.

Doxycycline, like any medication, can have side effects. Common ones include an upset stomach and increased sensitivity to sunlight, which can lead to sunburn more easily. These side effects are usually mild and manageable. Doxycycline is already approved by the FDA for treating various infections, indicating it has passed strict safety tests.

These findings can reassure prospective trial participants about doxycycline's safety. ^{1 2 3 4 5}

Why are researchers enthusiastic about this study treatment?

Doxycycline is unique because it offers a potential preventive approach for sexually transmitted infections (STIs) by using a short, seven-day course of daily doses. Unlike standard treatments for STIs, which typically focus on treating an infection after it occurs, doxycycline is being explored for its ability to prevent infections in the first place. This could be a game-changer, especially for individuals at high risk of recurrent STIs, as it might reduce the frequency and impact of these infections in a proactive manner. Researchers are excited about doxycycline's potential to offer a new layer of protection.

What is the effectiveness track record for doxycycline in treating sexually transmitted infections?

Studies have shown that doxycycline can significantly lower the risk of certain bacterial sexually transmitted infections (STIs). Specifically, taking 200 mg within 72 hours after sex can reduce the chances of contracting syphilis and chlamydia by more than 70% and also help prevent gonorrhea. Research indicates that doxycycline is particularly effective for men who have sex with men (MSM) and transgender women. In this trial, participants will take 7 consecutive daily doses of 100 mg of doxycycline to evaluate its effectiveness in preventing STIs. While doxycycline appears promising for STI prevention, more information is needed to understand its efficacy across different groups. Overall, doxycycline is a well-known antibiotic proven effective for treating various infections. ^{1 5 6 7 8}

Who Is on the Research Team?

Colleen Kelley, MD, MPH

Principal Investigator

Emory University

Are You a Good Fit for This Trial?

This trial is for adults assigned male or female at birth, in good health, and willing to use condoms. It includes HIV positive individuals with undetectable viral loads and CD4 counts over 300. Pregnant individuals or those planning pregnancy are excluded, as well as anyone planning to take doxycycline outside the study.

Inclusion Criteria

In good general health

Able to provide informed consent

I am willing to consistently use condoms during the study.

Exclusion Criteria

I have a history of liver disease.

I haven't used strong immune system drugs, high-dose steroids, chemotherapy, radiation, or experimental treatments for cancer in the last 90 days.

Any other clinical condition or prior therapy that, in the opinion of the investigator, would make the patient unsuitable for the study or unable to comply with the study requirements

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

1 week

1 visit (in-person)

Treatment

Participants receive daily doses of 100mg doxycycline for 7 days

1 week

1 visit (in-person) for enrollment, 5 doses at home, 1 visit (in-person) for sample collection

Sample Collection

Rectal and vaginal swab samples collected 2 to 4 hours after the final dose; biopsy tissue collected 24 hours after the last dose

1 day

1 visit (in-person)

Follow-up

Participants are monitored for safety and effectiveness after treatment

1 week

What Are the Treatments Tested in This Trial?

Interventions

• Doxycycline

Trial Overview The study tests how daily doses of doxycycline concentrate in mucosal tissues over a week to prevent bacterial STIs. Participants will provide various biological samples and undergo biopsies to gather data.

How Is the Trial Designed?

Group I: Doxycycline Experimental Treatment 1 Intervention

Study participants taking 7 consecutive, daily doses of 100mg of Doxycycline.

Doxycycline is already approved in United States, European Union, Canada, Japan for the following indications:

Approved in United States as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Approved in European Union as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Approved in Canada as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Approved in Japan as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Who Is Running the Clinical Trial?

Emory University

Lead Sponsor

Trials

1,735

Recruited

2,605,000+

Centers for Disease Control and Prevention

Collaborator

Trials

902

Recruited

25,020,000+

Published Research Related to This Trial

Doxycycline has been shown to lower the risk of sexually transmitted diseases (STDs), making it a potentially effective preventive treatment.

Concerns exist regarding the possibility that widespread use of doxycycline could lead to increased drug resistance, which may undermine its effectiveness in treating infections in the future.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Antibiotic after sex could help curb infections. Cohen, J.[2022]

Doxycycline is an effective antibiotic for treating various infections, particularly respiratory tract diseases like pneumonia, as demonstrated in a study involving 49 patients.

The drug shows good safety and compatibility, especially in children, and achieves effective serum levels when administered at a dose of 4 mg/kg in two injections.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Clinical and pharmacokinetic researches of doxycyclin vibravenös in childhood (author's transl)]. Weingärtner, L., Straube, D., Baum, W., et al.[2013]

A systematic review of 7 studies involving oral tetracycline-class antibiotics, including doxycycline, indicated that these antibiotics can increase resistance to tetracyclines in normal flora, particularly in subgingival, gastrointestinal, and upper respiratory tract bacteria.

While some studies showed a transient increase in non-tetracycline resistance, the overall impact on non-tetracycline AMR was minimal, suggesting that the use of doxycycline for STI prophylaxis may require careful monitoring of antimicrobial resistance in commensal bacteria.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A systematic review of the impacts of oral tetracycline class antibiotics on antimicrobial resistance in normal human flora. Truong, R., Tang, V., Grennan, T., et al.[2022]

In a study of 50 uncomplicated male gonorrhea cases treated with doxycycline, the treatment showed an 88% success rate, with 44 out of 50 patients responding well to the therapy.

The treatment regimen involved a total of 400 mg of doxycycline administered intravenously over three days, and side effects were minimal, indicating a favorable safety profile.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Doxycycline in the Treatment :uncomplicated Gonorrohea. Wadhwa, SL., Marquis, L.[2019]

In a study involving 111 healthy volunteers, enteric-coated doxycycline hyclate pellets in capsules were found to cause significantly fewer gastrointestinal adverse reactions compared to doxycycline monohydrate tablets, with only 43% of participants reporting side effects versus 66% for monohydrate.

The new formulation demonstrated improved tolerability, particularly reducing incidents of abdominal pain, nausea, and vomiting, making it a safer option for patients requiring doxycycline therapy.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Enteric Coating Reduces Upper Gastrointestinal Adverse Reactions to Doxycycline. Järvinen, A., Nykänen, S., Paasiniemi, L., et al.[2018]

Doxycycline hyclate (DH) has a favorable safety profile, especially in its delayed-release form (Doryx), compared to the standard powder form (Vibramycin), making it a safer option for treating conditions like acne and rosacea.

Despite historical safety concerns associated with tetracyclines, including gastrointestinal issues and effects on tooth development, subantimicrobial dosing of DH has shown to be effective and safe for acne treatment, supporting its continued use in dermatology.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The use and safety of doxycycline hyclate and other second-generation tetracyclines. Sloan, B., Scheinfeld, N.[2022]

In a study of 367 patients with Chlamydia trachomatis infections, both doxycycline (100 mg) and spiramycin (1 g) were found to be highly effective, with cure rates of 100% for doxycycline and 98% for spiramycin, indicating that both treatments are viable options.

Spiramycin was associated with a higher incidence of dysethesias in female patients, although these side effects resolved after treatment, suggesting that while effective, further research is needed to explore its safety profile, especially in shorter treatment durations and during pregnancy.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Comparison of spiramycin and doxycycline for treatment of Chlamydia trachomatis genital infections. Dylewski, J., Clecner, B., Dubois, J., et al.[2021]

Doxycycline is a well-established, broad-spectrum antibiotic that is effective against various bacterial infections, including sexually transmitted infections (STIs), and is particularly beneficial due to its high tissue diffusion and long half-life, allowing for convenient oral dosing.

With the rise of antibiotic resistance in first-line STI treatments, doxycycline is being reconsidered as a safe and effective option for managing STIs, especially in populations at higher risk, such as men who have sex with men (MSM) and those living with HIV.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Doxycycline in the management of sexually transmitted infections. Peyriere, H., Makinson, A., Marchandin, H., et al.[2019]

Doxycycline (200 mg/day for 2 weeks) effectively eradicated Chlamydia trachomatis in 89% of patients by the 3rd day and maintained a 100% eradication rate by the 14th day, demonstrating its efficacy in treating nongonococcal urethritis.

The treatment was well-tolerated with no reported side effects, and a significant reduction in symptoms was observed, with 83% of patients symptom-free by the 7th day and 100% by the 14th day.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Clinical studies on doxycycline in the treatment of nongonococcal urethritis by Chlamydia trachomatis]. Ito, Y., Katoh, N., Takeda, A., et al.[2020]

Doxycycline is effective against a wide range of bacterial infections and is particularly notable for its safety profile, as it does not require dosage adjustments in patients with renal failure.

It is well tolerated with common side effects like stomach upset and nausea, but new formulations are available to minimize these issues; however, it is contraindicated in children and pregnant or breastfeeding women.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Doxycycline]. Aupee, O., Almeras, D., Le Garlantezec, P., et al.[2013]

Doxycycline (Doxy-PEP) has been shown to effectively prevent bacterial sexually transmissible infections (STIs) like chlamydia, gonorrhoea, and syphilis in men who have sex with men with a history of multiple STIs.

Concerns remain regarding potential adverse effects of Doxy-PEP, including the risk of developing antimicrobial resistance and disrupting the microbiome, which clinicians need to discuss with patients considering this preventive treatment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Interim position statement on doxycycline post-exposure prophylaxis (Doxy-PEP) for the prevention of bacterial sexually transmissible infections in Australia and Aotearoa New Zealand - the Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM). Cornelisse, VJ., Ong, JJ., Ryder, N., et al.[2023]

Citations

1. cdc.gov cdc.gov/mmwr/volumes/73/rr/rr7302a1.htm

CDC Clinical Guidelines on the Use of Doxycycline .. ... 200 mg of doxycycline taken within 72 hours after sex has been shown to reduce syphilis and chlamydia infections by >70% and gonococcal infections by ...

2. ncbi.nlm.nih.gov ncbi.nlm.nih.gov/books/NBK597440/

Doxycycline Post-Exposure Prophylaxis to Prevent Bacterial ... Doxy-PEP is not 100% effective in preventing bacterial STIs. There is insufficient evidence to recommend doxy-PEP to protect against STI ...

3. nature.com nature.com/articles/s41467-025-64261-w

Bacterial sexually transmitted infections and related ... Recent trials have demonstrated that doxyPEP reduces the incidence of chlamydia and syphilis infections among MSM, TGW, and PLWH by ...

4. academic.oup.com academic.oup.com/cid/article/70/6/1247/5557867

Doxycycline Prophylaxis for Bacterial Sexually Transmitted ... Doxycycline prophylaxis for bacterial STIs shows promise. Better and more robust data are needed on efficacy; target population; community acceptability.

5. sciencedirect.com sciencedirect.com/science/article/pii/S2352396424000720

Pharmacokinetics of single dose doxycycline in the rectum ... Clinical trials showed a single oral dose of doxycycline taken after sex protects against STIs among men who have sex with men (MSM) but not women.

6. ncbi.nlm.nih.gov ncbi.nlm.nih.gov/books/NBK555888/

Doxycycline Hyclate - StatPearls - NCBI Bookshelf - NIH The Centers for Disease Control now recommends doxycycline as postexposure prophylaxis (Doxy PEP) for preventing bacterial STIs in high-risk ...

7. drugs.com drugs.com/doxycycline.html

Doxycycline: Uses, Dosage, Side Effects, Warnings Doxy PEP significantly protects against 3 STDs, syphilis, chlamydia, and gonorrhea, in high-risk, sexually active adults. STDs may also be ...

8. mayoclinic.org mayoclinic.org/drugs-supplements/doxycycline-oral-route/description/drg-20068229

Doxycycline (oral route) - Side effects & dosage It works by killing bacteria or preventing their growth. However, this medicine will not work for colds, flu, or other virus infections.