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Clarithromycin to prevent secondary infections in adult patients with community-acquired pneumonia-related sepsis

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What is this trial about?

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

The study focuses on patients who have developed Community-acquired pneumonia related sepsis, a serious condition where a lung infection spreads and triggers a dangerous body-wide response called sepsis. Some of these patients also show signs of Sepsis Induced Immunoparalysis, which means their immune system becomes weakened and less able to fight infections. The trial tests whether adding the antibiotic Clarithromycin, given either through an IV (a drip placed into a vein) or as a tablet taken by mouth, can help prevent new infections during the first month after the initial illness. Participants will receive either the active drug or a matched placebo, which looks the same but does not contain the medication.

The purpose of the trial is to see if the additional antibiotic reduces the number of secondary infection episodes, including further episodes of sepsis, within 28 days. After enrollment, patients will continue their standard antibiotic treatment while receiving the study medication or placebo for up to seven days, followed by routine medical care and follow‑up visits to monitor health outcomes for the remainder of the month.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and baseline assessment

    After giving informed consent, basic health information is recorded, including a review of the recent lung infection and any signs of sepsis, which is the body’s extreme response to infection.

    Blood samples are taken to measure the immune status and to confirm the presence of sepsis‑induced immunoparalysis (sii).

  2. Step 2

    Randomization to study medication

    You are assigned, by chance, to receive either clarithromycin (the active drug) or a matching placebo. the assignment also determines the route of administration: either intravenous (iv) injection or oral tablet.

  3. Step 3

    First dose of study medication (day 1)

    If assigned to the iv group, a single bolus of clarithromycin 1000 mg is given through a vein, mixed in 20 ml of sterile water for injection. the same volume is used for the iv placebo.

    If assigned to the oral group, a film‑coated tablet containing clarithromycin 1000 mg is swallowed with water. a matching tablet without active drug is used for the oral placebo.

  4. Step 4

    Daily dosing (days 2‑7)

    The same dose (1000 mg) is taken once each day for a total of seven days.

    The iv formulation continues as a daily infusion; the oral formulation continues as a daily tablet.

    The placebo follows the identical schedule, using either the iv solution or the tablet that contains no active drug.

  5. Step 5

    Daily monitoring during treatment

    Each day, vital signs (temperature, heart rate, blood pressure) are checked.

    Blood samples are collected to monitor organ function and to look for signs of new infection.

    Any new symptoms, such as worsening cough or fever, are reported to the study team.

  6. Step 6

    Stop of study medication (day 8)

    After the seventh dose, the study medication is discontinued. day 8 marks the end of the treatment period.

  7. Step 7

    Follow‑up period (days 8‑28)

    Regular visits or telephone checks are scheduled to detect any secondary infection or new episode of sepsis that may occur after the drug is stopped.

    Additional blood tests may be performed to assess immune markers and organ function.

    The study records whether any new infection develops, whether the original lung infection worsens, and any need for additional antibiotics.

  8. Step 8

    Final assessment (day 28)

    A comprehensive evaluation is performed at the end of the 28‑day period.

    Outcomes recorded include survival, any new infections, and overall health status using a questionnaire.

  9. Step 9

    Optional long‑term follow‑up (day 90)

    A final check may be made around day 90 to record any later hospital readmission or death.

    This information contributes to the secondary outcomes of the trial.

Who can join the trial?

8 criteria

  • Be at least 18 years old.
  • Be of any gender.
  • Provide a written informed consent; if you cannot decide for yourself, a legally authorized representative must give consent.
  • If you are a woman of child‑bearing age, have a negative pregnancy test (blood or urine).
  • If you are a woman of child‑bearing age, agree to use a reliable form of birth control during the study and for seven days after the last dose of the study medication.
  • Have community‑acquired pneumonia – a lung infection that you got outside of a hospital.
  • Have sepsis as defined by the Sepsis‑3 criteria, meaning your overall organ function score (SOFA‑1 score) is at least 2 points higher than your normal baseline.
  • Have an absolute lymphocyte count (a type of white blood cell) of less than 1000 per cubic millimeter.

Who cannot join the trial?

20 criteria

  • Age under 18 years old.
  • Female patients who do not agree to use birth control during the study drug period and for seven days after.
  • Known HIV infection with a CD4 cell count (a type of immune cell) of 200 or less.
  • Having had a solid organ transplant (such as kidney or liver) or a bone‑marrow transplant.
  • Taking oral or IV corticosteroids equivalent to more than 0.4 mg per kilogram of prednisone each day for the past 15 days, or using other medicines that suppress the immune system (except steroids given for the current infection).
  • Use of a biological agent (a special type of medicine that affects the immune system) in the last month.
  • Having an active cancer or any serious illness that is expected to shorten life to less than six months.
  • Severe low potassium (hypokalemia) or low magnesium (hypomagnesemia) levels, unless these are corrected before enrollment.
  • Any condition that makes taking a macrolide antibiotic (the study drug clarithromycin) unsafe.
  • Participation in another interventional clinical trial within the past 30 days.
  • Having already taken part in the CLASSIFY study.
  • Neutropenia (a very low number of neutrophils, a type of white blood cell, defined as less than 500 per microliter).
  • Severe liver failure (hepatic failure) or severe kidney failure (renal dysfunction) as judged by the treating doctor.
  • Already receiving a macrolide antibiotic for the current pneumonia episode.
  • A corrected QT interval on an ECG of 500 milliseconds or more, or a known history of long QT syndrome (a heart rhythm problem).
  • Allergy to macrolide antibiotics.
  • Use of medicines that should not be taken with clarithromycin because they can cause harmful interactions, such as certain heart‑rhythm drugs, ergot drugs, some cholesterol medicines, colchicine, ticagrelor, ranolazine, etc.
  • History of torsades de pointes arrhythmia (a dangerous irregular heart rhythm).
  • Failure to sign the written informed consent form.
  • Pregnancy (confirmed by test) or breastfeeding for female patients.
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Investigated drugs

  • KLARICID® (intravenous solution)

    is a medicine that contains clarithromycin, an antibiotic that fights bacterial infections. In this trial it is given directly into a vein through an IV infusion. The purpose of using this IV form is to see if giving clarithromycin early and directly into the bloodstream can help lower the chance of patients developing new infections, such as sepsis, after they have already been treated for a lung infection that caused sepsis.

  • KLARICID® (oral tablets)

    is the same antibiotic, clarithromycin, but in a tablet that is taken by mouth. The tablets are coated so they are easy to swallow. This form is used in the study to find out whether taking clarithromycin by mouth, in addition to standard care, can also reduce the risk of later infections in patients who have had sepsis from a lower respiratory tract infection.

What is already known about the treatment

  • KLARICID® 500 mg/vial

    This medication is given as a sterile liquid that is injected directly into a vein, either as a quick push or slow infusion. Clarithromycin is a well‑known antibiotic that is already approved and widely described in medical literature for treating bacterial lung infections. It is mainly used to treat community‑acquired pneumonia and related infections, helping to stop bacterial growth. It works by binding to bacterial ribosomes, which blocks the bacteria’s ability to make proteins needed for survival; it belongs to the macrolide antibiotic class.

  • KLARICID® 500 mg film‑coated tablets

    The tablets are taken by mouth, swallowed with water, and dissolve to release clarithromycin into the bloodstream. Clarithromycin is an established antibiotic that has been used for many years and is well documented for treating respiratory infections. The main use is for community‑acquired pneumonia and other bacterial infections of the lungs and throat. It acts by attaching to bacterial ribosomes and preventing protein production, classifying it as a macrolide antibiotic.

Investigated diseases

  • Community-acquired pneumonia

    An infection of the lung that is acquired outside a hospital setting. It usually begins with cough, fever, and difficulty breathing. Inflammation spreads through the air spaces, causing fluid and pus to fill the lungs. Symptoms can gradually worsen over several days if the infection is not resolved.

  • Sepsis

    A severe, body‑wide response to an infection that triggers widespread inflammation. It often starts with fever, chills, and rapid heart rate. As the response spreads, it can affect the function of multiple organs. The condition can progress as the inflammatory process intensifies.

  • Sepsis-induced immunoparalysis

    A state in which the immune system becomes less active after a severe septic episode. This reduced immune activity develops over days following the initial infection. It makes the body less able to fight new infections, allowing secondary infections to appear more easily.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-525058-20-00Protocol codeCLASSIFYEstimated enrolment252 patientsSponsorHellenic Institute For The Study Of Sepsis

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