Short 5‑day versus 7‑day amoxicillin treatment in children aged 2‑17 with acute streptococcal pharyngotonsillitis: a phase III open‑label randomized trial

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What is this study about?

The study looks at children who have Acute streptococcal pharyngotonsillitis, a common throat infection caused by bacteria that can cause sore throat, fever, and swollen tonsils. The medication being tested is amoxicillin, an antibiotic taken by mouth that kills the bacteria. Participants will receive either a short 5‑day course or a standard 7‑day course of the medicine, both given at home.

The purpose of the trial is to find out whether the shorter treatment works as well as the longer one in preventing the infection from coming back. Children aged 2 to 17 will be randomly placed into one of the two treatment groups and will be followed for a short period after finishing the medication to see if they experience a relapse (return of the infection). Researchers will also record how quickly a cure (fever gone within 48 hours) occurs and will watch for any serious health problems. Suppurative complications are infections that produce pus, such as ear infections or abscesses, while non-suppurative complications are immune‑related problems like rheumatic fever or kidney inflammation. The study follows each child for several weeks to collect this information.

1 randomization and assignment

after you join the study, a computer will place you randomly into one of two groups. one group receives a 5‑day course of amoxicillin, the other receives a 7‑day course. the assignment is not chosen by you or the doctor.

2 baseline assessment

a brief medical check is performed. this includes a throat swab to confirm acute streptococcal pharyngotonsillitis, the infection the study is treating. the result helps determine eligibility for the trial.

3 start of medication

you begin taking amoxicillin orally. the dose is 1000 mg per intake. the medication is taken exactly as instructed, usually once each day.

4 daily medication intake

for the assigned duration, you swallow the tablet each day. if you are in the 5‑day group, you continue for five days; if you are in the 7‑day group, you continue for seven days. do not miss a dose and do not stop early.

5 symptom monitoring

while taking the medicine, you watch for changes in fever and throat pain. the study defines cure as the disappearance of fever within 48 hours after the first dose. note the time when fever resolves.

6 completion of treatment

after the assigned number of days, you finish the medication course. no further doses are taken unless instructed by the study doctor.

7 relapse observation period

for the next 15 days after finishing the medication, you remain alert for a return of infection. a relapse is a new streptococcal infection that occurs within this period. if symptoms reappear, you report them to the study doctor.

8 follow‑up visits

a visit is scheduled at the end of the 15‑day observation to check for relapse and any complications. another visit occurs four months after treatment to evaluate new episodes of streptococcal infection and any long‑term complications.

Who Can Join the Study?

Be a boy or girl who is at least 2 years old but not yet 18 years old.
Have a new case of strep throat (called group A streptococcal infection or FAA) that is confirmed by a quick lab test (a rapid diagnostic test or TDR) and whose symptoms started no more than 72 hours before beginning the study medicine.
Score 3 or higher on the McIsaac scale (a checklist doctors use to decide if a sore throat is likely strep) and have a fever higher than 38°C (about 100.4°F).
Have written permission from a parent or legal guardian, and if you are 12 years old or older, also agree to take part in the study.

Who Cannot Join the Study?

Currently taking antibiotics such as penicillin, amoxicillin, amoxicillin‑clavulanic acid, macrolides, or any type of cephalosporin (first, second, or third generation).
Unable to attend follow‑up visits or cannot be contacted for later check‑ups.
Having an allergy to amoxicillin (a common penicillin‑type antibiotic).
If you or your caregiver cannot understand or follow the study instructions.
If the doctor thinks any health problem, test result, or personal situation could make participation unsafe.
Having taken any of the following medicines in the past 48 hours: probenecid, allopurinol, tetracycline antibiotics, oral blood‑thinners (anticoagulants), or methotrexate (a medication that suppresses the immune system).
Showing signs of a viral infection such as runny nose (rhinorrhoea), cough, pink eye (conjunctivitis), hoarse voice (dysphonia), mouth sores (acute stomatitis), ulcerated lesions or blisters (vesicles) in the mouth, or diarrhea.
Having many repeated episodes of sore throat (acute tonsillitis) in recent years, for example:
- seven or more episodes in the last year, or
- five or more episodes per year in the last two years, or
- three or more episodes per year in the last three years,
and each episode includes 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 throat test for the bacteria.
Already diagnosed with a streptococcal throat infection (EbhGA) by a rapid test or throat culture within the past 28 days.
Having a personal history of serious complications from a streptococcal throat infection, whether pus‑forming (suppurative) or other types.
Having a personal history of severe invasive disease caused by the bacteria, such as infection of the blood (bacteremia) or infection of the brain coverings (meningitis).
Having a weakened immune system (immunocompromised), for example due to disease or medication.
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
Fbmwggzqr Pxit Lz Ixlubxkjlxjup Bnxjpvkgw Dfi Hdzurjyl Ujqvgfcbbhfrp Lz Ppp	Madrid	Spain

Trial status

Country	Status	Recruitment Start
Spain	Not yet recruiting	01.04.2026

Trial locations

Investigated drugs:

Amoxicillin

Amoxicillin is an oral antibiotic that is used to treat infections caused by bacteria, such as strep throat. In this study, children aged 2 to 17 years with acute streptococcal pharyngotonsillitis receive amoxicillin by mouth. The trial compares a short 5‑day treatment plan with the usual 7‑day plan to see if the shorter course works just as well at preventing the infection from coming back. The medication is being tested to make sure it is safe and effective for children when taken for either length of time.

Investigated diseases:

Streptococcal infection

Acute streptococcal pharyngotonsillitis – This is a bacterial infection that affects the throat and the tonsils, caused by group A streptococcus. It usually begins with a sore throat, pain when swallowing, and fever. The inflammation can cause the tonsils to become red and swollen, sometimes with white spots. As the infection continues, the throat may become more painful and the person may feel tired or have a headache. The condition typically 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 5‑day versus 7‑day amoxicillin treatment in children aged 2‑17 with acute streptococcal pharyngotonsillitis: a phase III open‑label randomized trial

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?