Inclusion criteria:

• Patient weighs at least 40 kg.
• Younger than 16 years old (no older than their 16th birthday).
• Suspected acute bacterial sinusitis.
• Able to swallow amoxicillin/clavulanate tablets.

Exclusion criteria:

• Personal or family history of adverse reactions or hypersensitivity or allergy to any penicillin or cephalosporin antibiotics.
• History of reaction to multiple allergens (if considered clinically relevant by the principal investigator).
• Patient is participating in another clinical trial or has received or anticipates receiving an investigational drug, vaccine, or medical device prior to the first dose of study medication or during the conduct of the study.
• History or presence of gastrointestinal, hepatic or renal disease or other conditions known to or that may interfere with the absorption, distribution, metabolism or excretion of study medication.
• Treatment with probenecid or allopurinol within 7 days of study entry.
• Female patients with a positive urine hCG (human chorionic gonadotropin) test at screening, or who are lactating (breast feeding) or are unwilling to be abstinent until completion of the follow-up visit.
• History of diarrhea due to Clostridium difficile following treatment with antibiotics.
• History of hypersensitivity or allergy to heparin or related preparations (if the clinical research unit uses heparin to maintain intravenous cannula patency).
• Patient is diagnosed with mononucleosis.
• Estimated Glomerular Filtration Rate (GFR) <40 ml/min.