What is the recommended treatment for an acute bacterial sinus infection in an otherwise healthy adult?

Treatment for Acute Bacterial Sinus Infection

For an otherwise healthy adult with acute bacterial sinusitis, prescribe amoxicillin-clavulanate 875 mg/125 mg twice daily for 5–10 days as first-line therapy, achieving 90–92% predicted clinical efficacy against the major pathogens. 1, 2

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Confirm the Diagnosis Before Prescribing Antibiotics

Before initiating antibiotics, verify that the patient meets at least one of three diagnostic criteria for acute bacterial rhinosinusitis (ABRS):

• Persistent symptoms ≥10 days without improvement: purulent nasal discharge plus either nasal obstruction or facial pain/pressure/fullness. 1, 2
• Severe symptoms ≥3–4 consecutive days: fever ≥39°C (102.2°F) with purulent nasal discharge and facial pain at illness onset. 1, 2
• "Double sickening": initial improvement from a viral upper respiratory infection followed by new or worsening fever, nasal discharge, or cough within 10 days. 1, 2

Critical context: Approximately 98–99.5% of acute rhinosinusitis episodes are viral and resolve spontaneously within 7–10 days without antibiotics. 1, 2 Do not prescribe antibiotics for symptoms lasting <10 days unless the severe criteria above are met. 1, 2

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First-Line Antibiotic Regimen

• Amoxicillin-clavulanate 875 mg/125 mg orally twice daily for 5–10 days (or until symptom-free for 7 consecutive days, typically 10–14 days total). 1, 2, 3
• This regimen provides 90–92% predicted clinical efficacy against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1, 2, 4
• The clavulanate component is essential because 30–40% of H. influenzae and 90–100% of M. catarrhalis produce β-lactamase, rendering plain amoxicillin ineffective. 2

High-dose regimen (2 g amoxicillin/125 mg clavulanate twice daily) is indicated when any of the following risk factors are present: recent antibiotic use within the past 4–6 weeks, age >65 years, daycare exposure, moderate-to-severe symptoms, comorbidities (diabetes, chronic cardiac/hepatic/renal disease), or immunocompromised state. 2, 4

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Alternatives for Penicillin-Allergic Patients

Non-Severe (Non-Type I) Penicillin Allergy

• Use a second- or third-generation cephalosporin for 10 days: cefuroxime-axetil, cefpodoxime-proxetil, cefdinir, or cefprozil. 1, 2, 3
• Cross-reactivity with penicillins is negligible (<1%). 2

Severe (Type I/Anaphylactic) Penicillin Allergy

• Levofloxacin 500 mg once daily for 10–14 days or moxifloxacin 400 mg once daily for 10 days. 1, 2, 5, 4
• Both achieve 90–92% predicted efficacy against multidrug-resistant S. pneumoniae and β-lactamase-producing organisms. 2, 4
• Reserve fluoroquinolones for severe penicillin allergy or documented treatment failure to limit resistance development. 1, 2

Suboptimal Alternative

• Doxycycline 100 mg once daily for 10 days offers lower efficacy (77–81%) and a 20–25% bacteriologic failure rate due to limited activity against H. influenzae. 2, 3
• Use only when cephalosporins and fluoroquinolones are contraindicated. 2
• Contraindicated in children <8 years due to tooth enamel discoloration. 2

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Essential 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. 1, 2
• Saline nasal irrigation 2–3 times daily provides symptomatic relief and aids mucus clearance. 1, 2, 6
• Analgesics (acetaminophen or ibuprofen) for pain and fever control. 1, 2, 6

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Watchful-Waiting Strategy

• For uncomplicated ABRS with reliable follow-up, initial observation without antibiotics is appropriate. 1, 2
• Initiate antibiotics only if no improvement by day 7 or if symptoms worsen at any time. 1, 2
• The number needed to treat (NNT) with antibiotics is 10–15 to achieve one additional cure compared with placebo. 2

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Monitoring and Reassessment

• Reassess at 3–5 days: If no clinical improvement (persistent purulent drainage, unchanged facial pain, or worsening), switch to high-dose amoxicillin-clavulanate (2 g/125 mg twice daily) or a respiratory fluoroquinolone (levofloxacin or moxifloxacin). 1, 2, 4
• Reassess at 7 days: Persistent or worsening symptoms warrant confirmation of diagnosis, exclusion of complications (orbital cellulitis, meningitis, intracranial abscess), and consideration of imaging or ENT referral. 1, 2
• Expected timeline: Noticeable improvement within 3–5 days of appropriate therapy, with complete resolution by 10–14 days or when symptom-free for 7 consecutive days. 2

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Antibiotics to Avoid

• Macrolides (azithromycin, clarithromycin): 20–25% resistance rates in S. pneumoniae and H. influenzae; the American Academy of Pediatrics explicitly contraindicates azithromycin for ABRS. 1, 2, 3
• Trimethoprim-sulfamethoxazole: ≈50% resistance in S. pneumoniae and ≈27% in H. influenzae. 2
• First-generation cephalosporins (e.g., cephalexin): Inadequate coverage since ≈50% of H. influenzae strains produce β-lactamase. 2

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Referral to Otolaryngology

Refer immediately if any of the following occur:

• No improvement after 7 days of appropriate second-line antibiotic therapy. 1, 2
• Worsening symptoms at any point (increasing facial pain, fever, purulent drainage). 1, 2
• Signs of complications: severe headache, visual changes, periorbital swelling/erythema, proptosis, diplopia, altered mental status, or cranial nerve deficits. 1, 2
• Recurrent sinusitis (≥3 episodes per year) requiring evaluation for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities. 1, 2

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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. 1, 2
• Avoid routine imaging (X-ray or CT) for uncomplicated ABRS; up to 87% of viral upper-respiratory infections show sinus abnormalities on imaging, leading to unnecessary interventions. 2
• Ensure adequate treatment duration (≥5 days for adults) to prevent relapse. 2, 7
• Fluoroquinolones should not be used as first-line therapy in patients without documented β-lactam allergy to limit resistance development. 1, 2
• Gastrointestinal adverse effects with amoxicillin-clavulanate are common: diarrhea in 40–43% of patients, severe diarrhea in 7–8%. 2