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Early switch to oral amoxicillin (drug combination) for adults with vertebral osteomyelitis: a randomised non‑inferiority trial

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

The trial focuses on patients with pyogenic Vertebral Osteomyelitis, a type of bone and joint infection that affects the spine. The infection is usually treated with strong antibiotics given through a vein (intravenous) for several weeks. The study will compare the standard approach of giving IV antibiotics for two weeks with an approach that switches to pills taken by mouth (oral) after one week. A range of oral antibiotics that are commonly used for such infections, including amoxicillin, doxycycline, cefadroxil, and clindamycin, may be part of the treatment.

The purpose of the study is to show that switching to oral therapy after seven days is not worse than switching after fourteen days. Participants will receive IV antibiotics for either seven or fourteen days, then continue with oral medication for the remaining treatment period. After the antibiotics are stopped, health will be checked for up to 24 weeks to see if the infection returns, if additional spine surgery is needed, or if any serious problems occur. Quality of life and ability to perform daily activities will also be recorded during the follow‑up.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline assessment

    After joining the study, a baseline evaluation is performed to record health status, laboratory results, and imaging of the spine.

    Information collected at this visit is used to guide the choice of antibiotic therapy.

  2. Step 2

    Start intravenous antibiotic therapy

    The first treatment phase uses intravenous antibiotics selected from the study list.

    Each medication is given at the dose shown in the study documentation:

    amoxicillin – 6 g, cefadroxil – 4000 mg, doxycycline – 300 mg, rifampicin – 1200 mg, phenoxymethylpenicillin – 8 million IU, ciprofloxacin – 1500 mg, metronidazole – 2000 mg, moxifloxacin – 400 mg, clindamycin – 1800 mg, cefalexin – 4000 mg, flucloxacillin – 12 g, levofloxacin – 1000 mg, linezolid – 1200 mg, co‑trimoxazole – 640 mg.

    The medication is administered according to the dosing schedule defined by the protocol.

  3. Step 3

    Intravenous treatment period

    Participants are randomly assigned to one of two strategies:

    • early switch – intravenous therapy is continued for 7 days.

    • standard switch – intravenous therapy is continued for 14 days.

    During this period the infusion is given daily in the hospital setting.

  4. Step 4

    Switch to oral antibiotic therapy

    After the assigned intravenous period, treatment is changed to oral antibiotics.

    The oral options correspond to the same active substances used intravenously and are taken at the doses listed:

    amoxicillin – 6 g, cefadroxil – 4000 mg, doxycycline – 300 mg, rifampicin – 1200 mg, phenoxymethylpenicillin – 8 million IU, ciprofloxacin – 1500 mg, metronidazole – 2000 mg, moxifloxacin – 400 mg, clindamycin – 1800 mg, cefalexin – 4000 mg, flucloxacillin – 12 g, levofloxacin – 1000 mg, linezolid – 1200 mg, co‑trimoxazole – 640 mg.

    The oral medication is taken at home for the remainder of the prescribed course.

  5. Step 5

    Completion of antibiotic course

    Oral therapy continues until the total treatment duration defined by the study protocol is reached.

    The exact length of therapy is based on clinical response and the investigator’s judgment.

  6. Step 6

    Follow‑up assessments

    After stopping antibiotics, participants are monitored for 24 weeks.

    Follow‑up visits include clinical examination, laboratory tests, and imaging to detect any signs of infection recurrence or complications.

    Patient‑reported outcomes such as quality of life and functional status are collected during these visits.

Who can join the trial?

8 criteria

  • You must be 18 years old or older.
  • You must sign and date a written consent form before any study procedures.
  • You must have vertebral osteomyelitis (an infection of the spine bone) that your doctor and an infectious‑disease (ID) specialist have confirmed using symptoms and imaging tests such as MRI, PET/CT, or PET/MRI.
  • Your treating doctor and the ID consultant must both decide to treat you for this infection.
  • When you are chosen for the study, your blood test for CRP (C‑reactive protein, a marker of inflammation) must have dropped to less than 75 % of its highest level or be lower than 20 mg/L.
  • You must have received appropriate intravenous (IV) antibiotic treatment for the infection for no more than 7 days before randomisation (being assigned to a study group). If you had surgery, the count starts after the first IV dose given after surgery.
  • A written recommendation from the ID specialist about which IV and oral antibiotics to use and how long the treatment should last must be available.
  • The oral antibiotic you will take must be on the approved “list of antibiotics” provided by the ID specialist.

Who cannot join the trial?

17 criteria

  • If the infection is caused by Actinomyces (a type of bacteria), Nocardia (another kind of bacteria), a fungal infection, brucellar infection (caused by Brucella bacteria), or a mycobacterial infection (such as tuberculosis), you cannot join the study.
  • If the doctor believes you are unlikely to follow the study’s requirements after you start, you will be excluded.
  • If you have taken part in any other interventional clinical trial in the 30 days before this study starts, you cannot participate.
  • If you are unable to understand what the study involves and what could happen because of it, you will be excluded.
  • If your expected life expectancy is less than six months, you cannot join.
  • If you have any kind of dependency on the study doctor or are employed by the study sponsor or the doctor, you are not eligible.
  • If you are being held in an institution by a legal or official order (for example, incarcerated or detained), you cannot take part.
  • Women who have the potential to become pregnant (called childbearing potential) are excluded unless they are permanently sterile (such as after a hysterectomy) or are post‑menopausal (no periods for 12 months and no other medical reason).
  • If you cannot give informed consent (meaning you cannot agree to join the study after it is explained to you) at the screening visit, you are not eligible.
  • If a test shows the presence of Pseudomonas aeruginosa (a type of bacteria) and you have any spinal foreign material (such as an implant or hardware), you cannot participate.
  • If you have had a previous episode of vertebral osteomyelitis (infection of the spine bones) within the past 24 months, you are excluded.
  • If you have a suspected or confirmed bacterial endocarditis (infection of the heart lining), you cannot join the study.
  • If you have severe immunocompromise (a weakened immune system), such as being a transplant recipient, having a blood cancer (hematological malignancy) or solid‑organ cancer that is currently being treated with drugs that suppress the immune system, being at risk for febrile neutropenia (fever with very low white‑blood‑cell count), or having received an IL‑6 inhibitor medication in the last three months, you are not eligible.
  • If you have signs or symptoms of an uncontrolled infection, or another infection that would require intravenous (IV) antibiotics for longer than seven days at the time you would be randomized, you cannot take part.
  • If you have clinical problems that make oral medication unsafe or ineffective—such as poor gastrointestinal absorption (your gut cannot absorb the medicine well), inability to swallow oral drugs, or expected drug toxicity (harmful side effects)—you are excluded.
  • If you have persistent Staphylococcus aureus (a common bacteria) in your blood, defined as a positive blood culture taken more than 48 hours after starting appropriate treatment, you cannot join.
  • If there are no reasonable oral antibiotic options—meaning the bacteria causing the infection can only be treated with IV antibiotics, or the only oral antibiotics available have poor bioavailability (they do not get into the bloodstream well) or are known to be ineffective—you are not eligible.
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Investigated drugs

  • Amoxicillin

    is a common oral antibiotic that works by stopping the growth of bacteria. In this study it is given after an initial IV treatment to see if switching to a pill early is as safe and effective as staying on IV longer.

  • Cefadroxil

    is an oral antibiotic that belongs to the cephalosporin family. It fights a wide range of bacteria and is used in the trial as a possible early‑switch option after the first week of IV therapy.

  • Amoxicillin and Clavulanic Acid

    (often called amoxicillin/clavulanic acid) combines a regular antibiotic with a substance that blocks bacterial resistance mechanisms. This combo is tested to determine if it can safely replace IV antibiotics sooner.

  • Doxycycline

    is a tablet that belongs to the tetracycline class of antibiotics. It can treat many types of bacterial infections and is evaluated in the trial as an early oral step after IV treatment.

  • Rifampicin

    is an oral drug that works by interfering with bacterial DNA. It is included in the study to see if it can be part of an early oral regimen for vertebral bone infection.

  • Phenoxymethylpenicillin

    (also called penicillin V) is a narrow‑spectrum oral antibiotic that targets certain common bacteria. The trial tests whether it can replace IV therapy after seven days.

What is already known about the treatment

  • AMOXICILLIN

    This medicine is taken by mouth and belongs to the penicillin class of antibiotics; it works by stopping bacteria from building a protective cell wall, which kills them. It is an approved drug that has been used for many years to treat a wide range of infections, including bone and joint infections. Its main use is for infections caused by susceptible bacteria such as streptococci and some staphylococci. It is classified as a bactericidal penicillin antibiotic.

  • CEFADROXIL

    Given orally, cefadroxil is a first‑generation cephalosporin that destroys bacteria by interfering with their cell wall formation. It is a well‑established, approved antibiotic used for many common infections and can be used for bone infections when the bacteria are sensitive. The drug is mainly prescribed for skin, urinary‑tract and bone infections caused by susceptible organisms. It belongs to the cephalosporin class of bactericidal antibiotics.

  • AMOXICLAV BASICS 875 mg/125 mg Filmtabletten

    This oral film‑coated tablet combines amoxicillin with clavulanic acid, a substance that blocks bacterial enzymes that would otherwise destroy amoxicillin; together they stop bacteria from making their cell wall. The combination is an approved, widely used treatment for many infections, including those of bone and joint when the bacteria produce beta‑lactamase. It is indicated for a broad range of bacterial infections such as respiratory, sinus, and orthopedic infections. It is classified as a penicillin antibiotic with a beta‑lactamase inhibitor.

  • DOXYCYCLINE

    Doxycycline is taken by mouth and belongs to the tetracycline family; it stops bacteria from making proteins needed for growth, which limits their spread. It is an established, approved drug used for many infections, including certain bone infections caused by atypical bacteria. Its main uses include respiratory, skin, and some bone infections where the bacteria are susceptible. It is classified as a bacteriostatic tetracycline antibiotic.

  • RIFAMPICIN

    This oral medication belongs to the rifamycin group and works by blocking the bacterial enzyme that makes RNA, which stops the bacteria from reproducing. Rifampicin is an approved drug widely used for tuberculosis and for other serious infections, sometimes including bone infections when combined with other antibiotics. It is mainly indicated for infections caused by susceptible Gram‑positive and some Gram‑negative bacteria. It is classified as a bactericidal rifamycin antibiotic.

  • PHENOXYMETHYLPENICILLIN

    Taken orally, phenoxymethylpenicillin (penicillin V) is a penicillin‑type antibiotic that kills bacteria by preventing them from forming a cell wall. It is an approved, long‑standing treatment for many mild to moderate infections and can be used for bone infections when the organism is sensitive. Its primary uses are for streptococcal infections, throat infections, and certain orthopedic infections. It belongs to the bactericidal penicillin class.

Investigated diseases

  • Pyogenic Vertebral Osteomyelitis

    It is an infection that affects the bones of the spine. The infection usually starts when bacteria spread to the vertebrae, causing inflammation. Over time the affected bone can become damaged and the surrounding tissue may become swollen. Patients often feel back pain that can become more intense as the infection progresses. The condition can spread to nearby muscles such as the iliopsoas if not resolved.

  • Bone and Joint Infection

    This term refers to infections that involve bones, joints, or the tissues around them. Bacteria can enter these areas through the bloodstream, a wound, or after surgery. As the infection develops, the affected bone may become painful and the joint may become stiff. Swelling and warmth may appear around the site as inflammation increases. If the infection continues, it can lead to damage of the bone or joint structure.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-526270-17-00Protocol codeUni-Koeln-5780Estimated enrolment280 patientsSponsorUniversity Of Cologne

sourced from the EU Clinical Trials Register and site verification

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