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Study Comparing Doxycycline and Benzathine Benzylpenicillin for Treating Early Syphilis in Adults

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the treatment of early syphilis, a sexually transmitted infection that can cause serious health problems if not treated. The study compares two treatments: doxycycline and benzathine benzylpenicillin (BPG). Doxycycline is an antibiotic taken orally in the form of a tablet, while benzathine benzylpenicillin is given as a single injection into the muscle.

The purpose of the study is to determine if taking doxycycline twice a day for 14 days is as effective as a single injection of benzathine benzylpenicillin for treating early syphilis. Participants in the study will be randomly assigned to receive either the doxycycline tablets or the benzathine benzylpenicillin injection. The effectiveness of the treatments will be evaluated by checking for a decrease in the level of the infection in the blood after six months.

Throughout the study, participants will have regular follow-up visits to monitor their health and the progress of the treatment. The study aims to provide valuable information on the effectiveness of these treatments for early syphilis, which could help improve future treatment options for this condition.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, the patient must provide written consent after understanding the study's nature.

    Eligibility includes being 18 years or older, having early syphilis, and being available for follow-up for 6 months.

  2. Step 2

    Initial assessment

    An initial assessment is conducted to confirm early syphilis through a positive non-treponemal assay result.

    The patient may have or not have an HIV infection.

  3. Step 3

    Treatment allocation

    The patient is randomly assigned to one of two treatment groups: doxycycline or BPG (benzathine benzylpenicillin).

  4. Step 4

    Doxycycline treatment

    If assigned to the doxycycline group, the patient takes 100 mg of doxycycline orally twice a day for 14 days.

    Adherence to the medication is monitored through a tablet count between weeks 1 and 2.

  5. Step 5

    BPG treatment

    If assigned to the BPG group, the patient receives a single intramuscular injection of 2.4 million IU of BPG.

  6. Step 6

    Follow-up visits

    The patient attends follow-up visits to monitor treatment response and any side effects.

    A non-treponemal assay is performed at month 3 to evaluate the evolution of the titer.

  7. Step 7

    Final assessment

    At month 6, a final assessment is conducted to determine the treatment's effectiveness.

    A successful response is defined as a four-fold decrease in titer in the non-treponemal assay compared to the initial result.

  8. Step 8

    Evaluation of other conditions

    The occurrence of other sexually transmitted diseases (STDs) is evaluated at month 6.

    Any serious adverse events (SAEs) are recorded and compared between the two groups.

Who can join the trial?

6 criteria

  • Patients must be **18 years or older**.
  • Patients must **understand the study** and **agree in writing** to participate before any study procedures begin.
  • Patients can have **HIV infection** or not, but must have **early syphilis**. This includes **primary syphilis**, **secondary syphilis**, or **early latent syphilis** that has lasted less than one year.
  • Patients must have a **positive result** on a specific blood test for syphilis, known as a **non-treponemal assay**.
  • Patients must be **available** to participate and attend follow-up visits for the **6 months** duration of the study.
  • Patients must be **covered by the French health insurance system**.

Who cannot join the trial?

4 criteria

  • Individuals who are not diagnosed with early syphilis cannot participate. Early syphilis is a stage of a sexually transmitted infection caused by bacteria.
  • Participants must be within the specified age range, which typically includes adults. If you are outside this age range, you cannot participate.
  • Both males and females are eligible, so gender is not a reason for exclusion.
  • Individuals who are considered part of a vulnerable population, such as those unable to give informed consent, are not eligible to participate.
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Investigated drugs

  • Doxycycline

    is an antibiotic used in this trial to treat early syphilis. It is taken orally and works by stopping the growth of bacteria. In this study, it is being compared to another treatment to see if it is just as effective.

  • BPG

    , or Benzathine Penicillin G, is an antibiotic given as an injection. It is used to treat early syphilis by killing the bacteria that cause the infection. In this trial, it serves as the standard treatment against which doxycycline is being compared.

What is already known about the treatment

  • Doxycycline

    Doxycycline is an antibiotic administered orally in tablet form, typically taken twice daily. It is currently used in medicine for various bacterial infections and is well-documented in medical literature. In this clinical trial, it is being evaluated for the treatment of early syphilis. Doxycycline works by inhibiting protein synthesis in bacteria, effectively stopping their growth. It belongs to the pharmacological class of tetracycline antibiotics.

  • Benzathine Penicillin G (BPG)

    Benzathine Penicillin G is an antibiotic administered through a single intramuscular injection. It is a well-established treatment in medical practice and literature for various bacterial infections, including syphilis. In this trial, it serves as a comparator for treating early syphilis. BPG works by interfering with the synthesis of bacterial cell walls, leading to the destruction of the bacteria. It is classified under the penicillin class of antibiotics.

Investigated diseases

Early Syphilis – Early syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. It typically begins with a painless sore at the site of infection, often on the genitals, rectum, or mouth. This sore, known as a chancre, appears about three weeks after exposure and can last for several weeks. If untreated, the infection progresses to a secondary stage, characterized by skin rashes and mucous membrane lesions. These symptoms may be mild and can resolve without treatment, but the infection remains in the body. Without intervention, syphilis can progress to more severe stages, affecting various organs over time.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-513532-23-00Protocol codeAPHP180588Estimated enrolment200 patientsSponsorAssistance Publique Hopitaux De Paris

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