Short Course Amoxicillin for Children with Acute Streptococcal Pharyngotonsillitis: A Phase III Randomized Trial

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What is this study about?

The condition being studied is acute streptococcal pharyngotonsillitis, a common throat infection caused by a type of bacteria that leads to sore throat, fever, and swollen tonsils. The medication tested in the study is the oral antibiotic amoxicillin, which is used to kill the bacteria that cause the infection.

The purpose of the trial is to determine whether a shorter 5‑day course of the antibiotic is not worse than the standard 7‑day course in preventing a repeat infection, called a relapse, within about two weeks after treatment ends. Children between 2 and 17 years old will be assigned by chance to receive either the 5‑day or the 7‑day regimen, take the medicine at home, and then be followed for several weeks to see if fever goes away, if symptoms return, or if any complications develop. A relapse means the infection comes back after the prescribed antibiotics have been finished.

1 enrollment and consent

after joining the study, a written agreement is signed to confirm participation.

the study purpose, procedures, and possible risks are explained in simple language.

2 random assignment to treatment length

the participant is randomly placed into one of two groups:

5‑day course of oral amoxicillin or 7‑day course of oral amoxicillin.

the assigned length determines how many days the medication will be taken.

3 receiving the medication

the prescribed tablets contain amoxicillin 1000 mg each.

the medication is taken by mouth as instructed by the study doctor.

4 taking the medication

the participant takes one 1000 mg tablet each day for the assigned period:

if placed in the 5‑day course, the tablets are taken for five consecutive days.

if placed in the 7‑day course, the tablets are taken for seven consecutive days.

5 monitoring symptoms during treatment

fever is checked regularly; resolution within 48 hours is recorded as a cure.

any signs of complications, such as pain, swelling, ear problems, or breathing difficulty, are reported to the study doctor.

6 completion of medication and short‑term observation

after the last tablet is taken, the participant continues to observe for at least 15 days.

the study looks for a relapse, defined as a new streptococcal infection occurring within 15 days after finishing the medication.

7 follow‑up visit at 15 days

a clinical assessment is performed to determine whether a relapse has occurred.

the doctor also checks for any suppurative (pus‑forming) or non‑suppurative complications.

8 extended follow‑up period

the participant is followed for up to four months after the treatment ends.

during this time, any new episodes of streptococcal throat infection, as well as delayed complications, are recorded.

Who Can Join the Study?

You are a boy or girl who is at least 2 years old and younger than 18 years.
You have a new diagnosis of strep throat (a throat infection that can cause sore throat and swollen tonsils) that was confirmed by a lab test, and your symptoms began no more than 72 hours (3 days) before starting the study medicine.
Your score on the McIsaac scale (a simple checklist doctors use to guess the chance of strep throat) is 3 or higher and you have a fever higher than 38 °C (about 100.4 °F).
Your parent or legal guardian has signed a written informed consent to let you join the study, and if you are 12 years old or older, you have also given your own agreement, called assent.

Who Cannot Join the Study?

Already taking antibiotics that work against the bacteria, such as penicillin, amoxicillin, amoxicillin‑clavulanic acid, macrolides (a group of antibiotics), or any first‑, second‑ or third‑generation cephalosporins (another type of antibiotic).
Unable to be followed up for the study, meaning you cannot attend the required visits or cannot be contacted for check‑ins.
Allergic to amoxicillin, a common antibiotic used in the trial.
Parents, legal guardians, or the patient cannot understand or follow all the study instructions and requirements.
If the doctor finds anything during the physical exam, lab tests, or other medical, social, or emotional factors that could make participation unsafe for the patient’s health.
Have taken any of the following medicines in the past 48 hours: probenecid (helps the body keep certain antibiotics), allopurinol (used for gout), tetracyclines (a class of antibiotics), oral anticoagulants (blood thinners), or methotrexate (a drug that suppresses the immune system).
Showing signs of a viral infection, such as a runny nose, cough, eye redness (conjunctivitis), hoarse voice, mouth sores (stomatitis), blisters or ulcers in the mouth, or diarrhea.
Having frequent tonsillitis, defined as seven or more episodes in one year, five or more episodes per year for two years, or three or more episodes per year for three years, and each episode must include at least one of the following: pus on the tonsils (purulent exudate), fever higher than 38°C, swollen neck lymph nodes (anterior cervical lymphadenopathy), or a positive test for the bacteria.
Having a confirmed infection with the bacteria (a rapid diagnostic test or throat culture) within the last 28 days before starting the study.
Having a personal history of serious complications from streptococcal throat infection, whether they produce pus (suppurative) or do not (non‑suppurative).
Having a personal history of invasive disease caused by the bacteria, such as bacteria in the blood (bacteremia) or infection of the brain membranes (meningitis).
Being immunocompromised, meaning the immune system is weakened and cannot fight infections well.
Being pregnant or breastfeeding.

Where you can join this trial?

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Other Sites

Site Name	City	Country
Hospital General Universitario Gregorio Maranon	Madrid	Spain
Hospital Universitario Puerta De Hierro De Majadahonda	Majadahonda	Spain
Hospital Universitario 12 De Octubre	Madrid	Spain
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Trial status

Country	Status	Recruitment Start
Spain	Not yet recruiting	01.04.2026

Trial locations

Investigated drugs:

Amoxicillin

Amoxicillin is an oral antibiotic that works by stopping the growth of bacteria that cause infections. In this study, children with a throat infection caused by streptococcus bacteria are given amoxicillin for either five days or seven days. The trial is testing whether the shorter five‑day treatment works just as well as the longer seven‑day treatment in preventing the infection from coming back. The medication is taken by mouth and is meant to clear the bacterial infection quickly and safely.

Investigated diseases:

Streptococcal infection

Acute streptococcal pharyngotonsillitis – A sudden infection of the throat and tonsils caused by group A Streptococcus bacteria. It begins with a sore throat, pain when swallowing, and redness of the throat tissues. Within a few days the inflammation can spread, leading to fever, swollen lymph nodes, and sometimes a white coating on the tonsils. The condition usually peaks within three to five days and then gradually improves as the body’s immune response clears the bacteria.

Trial ID:

2026-525355-93-00

Protocol code:

FIBHNJ-2025-001

Trial Phase:

Therapeutic confirmatory (Phase III)

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Short Course Amoxicillin for Children with Acute Streptococcal Pharyngotonsillitis: A Phase III Randomized Trial

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?