Comparative Effectiveness of Available Treatments for Sinus and Ear Infections in Children (Acute Sinusitis)

This is a multi-center, randomized, double-blind, placebo-controlled study designed to better understand whether the choice of antibiotic affects symptom burden in children with acute sinusitis (AS). Children enrolled in the study are randomly assigned to receive amoxicillin, amoxicillin-clavulanate, or a matching placebo. Neither the families nor the study team know which treatment a child is receiving during the study period. The primary objective is to compare average daily symptom severity across treatment groups using validated caregiver-reported symptom scales collected through daily electronic diaries. Analyses will assess whether symptoms suggestive of allergy (sneezing or itchy eyes) or more severe nasal findings (such as marked congestion or perinasal crusting) influence treatment response. The goal is to provide rigorous, comparative evidence on antibiotic use in this common pediatric infection to support more informed clinical decision-making and responsible antimicrobial prescribing. The study will also examine whether factors such as the severity of the child's illness and signs of allergies affect how well antibiotics work. The results will help guide better treatment decisions for children with sinus infections

• Amoxicillin (Drug): Amoxicillin administered orally at protocol-specified, weight-based dosing consistent with standard pediatric treatment guidelines for AS, for the defined treatment duration.
• Amoxi Clavulanate (Drug): Amoxicillin-clavulanate administered orally at protocol-specified, weight-based dosing consistent with standard pediatric treatment guidelines for AOM or AS, for the defined treatment duration.
• Amoxicillin Placebo (Drug): Matching placebo administered orally according to the same dosing schedule and treatment duration as the active comparator arms
• Amoxicillin-Clavulanate Placebo (Drug): Matching placebo administered orally according to the same dosing schedule and treatment duration as the active comparator arms.

Primary outcomes

• Average Daily Symptom Burden [Days 1-10]: Symptom burden measured daily using the Pediatric Rhinosinusitis Symptom Scale (PRSS Version 2.0). PRSS scores range from 0 to 40, with higher scores indicating worse symptoms. Daily scores are averaged over Days 1-10

Secondary outcomes

• Safety Outcome: Diarrhea [Randomization through Day 10]: Occurrence of diarrhea, defined as at least 3 watery stools in one day or at least 2 watery stools per day on two consecutive days.
• Recurrence of Acute Sinusitis or Acute Otitis Media [Days 11-90]: Occurrence of one or more new episodes of clinically diagnosed acute sinusitis or acute otitis media following resolution of the index episode.

Sex: All, ages: 2 Years to 12 Years

Inclusion Criteria:

* Age 2 years to <12 years.
* Clinical diagnosis of AS.

Exclusion Criteria:

* Known allergy or other contraindication to oral amoxicillin or clavulanate
* Prior use of systemic antibiotics in the last 7 days
* History of renal impairment
* History of hepatic impairment
* Phenylketonuria or allergy to aspartame
* History of craniofacial abnormalities
* Concurrent bacterial infection requiring systemic antibiotic therapy (e.g., pneumonia, streptococcal pharyngitis)
* Ill appearance, systemic toxicity, or immunodeficiency
* Incomplete pneumococcal vaccination, defined as receipt of fewer than three doses of a pneumococcal conjugate vaccine
* Parent or caregiver unable to complete study surveys in English or Spanish
* Previous randomization into either MEASURE trial within the last 6 months
* Periorbital redness and/or swelling, proptosis, or swelling of the forehead
* Individuals who qualify for both the AS and AOM trials (to avoid dual enrollment) will be excluded from the AS trial.

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• Nader Shaikh, MD, Principal investigator, University of Pittsburgh