What are the diagnostic criteria for acute bacterial rhinosinusitis and the recommended first‑line treatment, including adult and pediatric dosing of amoxicillin‑clavulanate, and alternative regimens for penicillin‑allergic, pregnant, or children under eight years old?

Acute Bacterial Rhinosinusitis: Diagnosis and Treatment

Diagnostic Criteria

Acute bacterial rhinosinusitis is diagnosed when a patient presents with any one of the following three patterns:

• Persistent illness: Nasal discharge (of any quality) or daytime cough lasting ≥10 days without improvement. 1
• Severe onset: Concurrent fever ≥39°C (102.2°F) and purulent nasal discharge for at least 3 consecutive days. 1
• Worsening course: New onset or worsening of nasal discharge, daytime cough, or fever after initial improvement from a viral upper respiratory infection. 1

The diagnosis is entirely clinical; routine imaging is not required. Sinus X-rays are not recommended for uncomplicated acute bacterial sinusitis because imaging does not change management, and more than 50% of children with viral upper respiratory infections show abnormal sinus radiographs. 2

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First-Line Antibiotic Treatment

Adults

Amoxicillin-clavulanate 875 mg/125 mg orally twice daily for 5–10 days is the preferred first-line regimen, providing 90–92% predicted clinical efficacy against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 2, 3, 4

• Standard dosing: 875 mg/125 mg twice daily for most patients. 3
• High-dose regimen (2 g/125 mg twice daily) is indicated when any of the following risk factors are present: recent antibiotic use (within 4–6 weeks), age >65 years, daycare exposure, moderate-to-severe symptoms, comorbidities (diabetes, chronic cardiac/hepatic/renal disease), or immunocompromised state. 2, 3
• Treatment duration: Continue for 5–10 days or until symptom-free for 7 consecutive days (typically 10–14 days total). Recent evidence supports shorter 5–7 day courses with comparable efficacy and fewer adverse effects. 2, 3

Pediatric Patients

Standard-dose amoxicillin 45 mg/kg/day divided twice daily is recommended for uncomplicated cases in children ≥3 months. 1, 2

High-dose amoxicillin 80–90 mg/kg/day divided twice daily (or high-dose amoxicillin-clavulanate 80–90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate divided twice daily) is required for children with any of the following risk factors: 1, 2, 4

• Age <2 years
• Daycare attendance
• Antibiotic use within the prior 4–6 weeks
• Residence in areas with high prevalence of penicillin-resistant S. pneumoniae

Treatment duration: Minimum 10–14 days for children, or continue for 7 days after becoming symptom-free. 1, 2

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Alternative Regimens for Penicillin-Allergic Patients

Non-Severe (Non-Type I) Penicillin Allergy

Second- or third-generation cephalosporins for 10 days are appropriate because cross-reactivity with penicillins is negligible (<1%). 2, 3, 4

• Options include: cefuroxime-axetil, cefpodoxime-proxetil, cefdinir, or cefprozil. 2, 3

Severe (Type I/Anaphylactic) Penicillin Allergy

Respiratory fluoroquinolones provide 90–92% predicted efficacy against multidrug-resistant S. pneumoniae and β-lactamase-producing organisms: 2, 3, 4

• Levofloxacin 500 mg once daily for 10–14 days (adults)
• Moxifloxacin 400 mg once daily for 10 days (adults)

Fluoroquinolones should be reserved for severe penicillin allergy or treatment failure to limit resistance development. 2, 3

Pediatric Penicillin-Allergy Alternatives

• Cefpodoxime proxetil 8 mg/kg/day in two doses for children with non-severe penicillin allergy. 3
• Ceftriaxone 50 mg/kg as a single IM/IV dose for children unable to tolerate oral medication. 1, 3

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Special Populations

Pregnant Patients

Amoxicillin or amoxicillin-clavulanate remains the first-line choice, as these are pregnancy category B. 3

• Avoid fluoroquinolones and doxycycline during pregnancy due to fetal risks. 2
• Cephalosporins (cefuroxime, cefpodoxime, cefdinir) are safe alternatives for penicillin-allergic pregnant patients. 3

Children Under 8 Years

Doxycycline is contraindicated in children <8 years due to risk of permanent tooth enamel discoloration. 2, 3

• Use high-dose amoxicillin-clavulanate or cephalosporins instead. 1, 2

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Monitoring and Reassessment

Pediatric Patients

Mandatory reassessment at 72 hours after initiating antibiotics is required to detect treatment failure or complications. 1, 2, 4

• Indicators of failure: New or worsening fever, increased purulent discharge, severe headache, or lack of improvement. 1, 2
• If failure occurs on high-dose amoxicillin-clavulanate: Consider a single dose of IM ceftriaxone 50 mg/kg, evaluate for complications, or consult pediatric infectious disease/ENT. 1, 4

Adult Patients

Reassess at 3–5 days: If no improvement (persistent purulent drainage, unchanged facial pain, or worsening), switch to high-dose amoxicillin-clavulanate or a respiratory fluoroquinolone. 2, 3

Reassess at 7 days: Persistent or worsening symptoms warrant confirmation of diagnosis, exclusion of complications, and possible imaging or ENT referral. 2, 3

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Adjunctive Therapies (Add to All Patients)

Intranasal corticosteroids (mometasone, fluticasone, or budesonide) twice daily significantly reduce mucosal inflammation and accelerate symptom resolution; supported by strong evidence from multiple randomized controlled trials. 2, 3

Saline nasal irrigation 2–3 times daily provides symptomatic relief and aids mucus clearance. 2, 3

Analgesics (acetaminophen or ibuprofen) for pain and fever control. 2, 3

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Complications Requiring Urgent Evaluation

Orbital complications (periorbital swelling, proptosis, restricted eye movements, visual changes) or intracranial complications (altered mental status, severe headache, seizures, focal neurologic deficits) require: 1, 2, 4

• Urgent contrast-enhanced CT imaging
• Intravenous antibiotics (e.g., vancomycin + ceftriaxone or cefotaxime)
• Immediate ENT and/or neurosurgery consultation

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Common Pitfalls to Avoid

• Do not prescribe antibiotics for symptoms <10 days unless severe features (fever ≥39°C with purulent discharge for ≥3 consecutive days) are present. 2, 3
• Do not obtain sinus imaging for uncomplicated cases; reserve imaging for suspected complications. 2, 4
• Do not use azithromycin or other macrolides as first-line therapy due to 20–25% resistance rates. 2, 3
• Do not use first-generation cephalosporins (e.g., cephalexin) because ~50% of H. influenzae strains produce β-lactamase. 2, 3
• Do not delay the 72-hour reassessment in children; early detection of failure prevents progression to complications. 1, 2, 4
• Ensure adequate treatment duration (≥5 days for adults, ≥10 days for children) to prevent relapse. 2, 3