When are antibiotics indicated for acute sinusitis and what are the first‑line antibiotic regimens for healthy adults and children, including alternatives for penicillin allergy and special populations?

When to Prescribe Antibiotics for Acute Sinusitis

Antibiotics are indicated only when acute bacterial rhinosinusitis (ABRS) is confirmed by one of three specific clinical patterns—not for routine viral upper respiratory infections, which account for 98–99.5% of acute sinusitis cases. 1

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Diagnostic Criteria: When Antibiotics Are Appropriate

Prescribe antibiotics only when the patient meets at least one of these three patterns:

1. Persistent Symptoms ≥10 Days Without Improvement

• Purulent nasal discharge plus nasal obstruction or facial pain/pressure/fullness lasting ≥10 days without any sign of improvement. 1, 2
• This is the most common presentation requiring antibiotics—symptoms plateau rather than resolve after the typical 7-day viral course. 3

2. Severe Symptoms ≥3–4 Consecutive Days

• High fever ≥39°C (102.2°F) plus purulent nasal discharge plus facial pain for at least 3–4 consecutive days at the onset of illness. 1, 2
• This dramatic presentation is uncommon but warrants immediate antibiotic therapy. 3

3. "Double Sickening" (Worsening After Initial Improvement)

• Initial improvement from a viral cold followed by new or worsening symptoms within 10 days—new fever, increased purulent discharge, or worsening cough. 1, 2
• This biphasic pattern strongly suggests secondary bacterial infection. 4

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First-Line Antibiotic Regimens

For Otherwise Healthy Adults

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5–10 days is the preferred first-line agent, providing 90–92% predicted efficacy against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1

• Standard dose: 875 mg/125 mg twice daily for most patients. 1
• High-dose regimen (2 g/125 mg twice daily) for patients with recent antibiotic use (past 4–6 weeks), age >65 years, daycare exposure, moderate-to-severe symptoms, or comorbidities. 1
• Duration: 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. 1, 5

Plain amoxicillin may be used only for mild disease in patients without recent antibiotic exposure, but amoxicillin-clavulanate is preferred due to increasing β-lactamase-producing organisms (30–40% of H. influenzae, 90–100% of M. catarrhalis). 1, 4

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For Penicillin-Allergic Adults

Non-Severe (Non-Type I) Allergy (e.g., Rash)

Second- or third-generation cephalosporins for 10 days—cross-reactivity is negligible. 1

• Cefuroxime-axetil, cefpodoxime-proxetil, cefdinir, or cefprozil. 1

Severe (Type I/Anaphylactic) Allergy

Respiratory fluoroquinolones provide 90–92% predicted efficacy against multidrug-resistant pathogens. 1

• Levofloxacin 500 mg once daily for 10–14 days or moxifloxacin 400 mg once daily for 10 days. 1
• Reserve fluoroquinolones for documented severe β-lactam allergy to prevent resistance development. 1

Doxycycline 100 mg once daily for 10 days is an acceptable but suboptimal alternative (77–81% predicted efficacy with 20–25% bacteriologic failure rate due to limited H. influenzae coverage). 1

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For Children

High-dose amoxicillin or amoxicillin-clavulanate is first-line therapy. 1

• Standard-dose amoxicillin: 45 mg/kg/day divided twice daily for uncomplicated disease. 1
• High-dose amoxicillin: 80–90 mg/kg/day divided twice daily for children <2 years, daycare attendance, recent antibiotic use, or high local resistance. 1
• High-dose amoxicillin-clavulanate: 80–90 mg/kg/day (amoxicillin component) plus 6.4 mg/kg/day clavulanate divided twice daily for children with risk factors. 1
• Duration: Minimum 10–14 days (longer than adult courses). 1
• Reassess at 72 hours; if no improvement, switch to high-dose amoxicillin-clavulanate. 1

For penicillin-allergic children: Cefpodoxime-proxetil 8 mg/kg/day in two doses or ceftriaxone 50 mg/kg as a single IM/IV dose for children unable to tolerate oral medication. 1

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Antibiotics to Avoid as First-Line Therapy

• Macrolides (azithromycin, clarithromycin): 20–25% resistance rates in S. pneumoniae and H. influenzae make them unsuitable. 1, 4
• Trimethoprim-sulfamethoxazole: 50% resistance in S. pneumoniae and 27% in H. influenzae. 1
• First-generation cephalosporins (cephalexin): Inadequate coverage against H. influenzae because ~50% of strains produce β-lactamase. 1

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Essential Adjunctive Therapies (Add to All Patients)

These therapies improve outcomes regardless of antibiotic use:

• Intranasal corticosteroids (mometasone, fluticasone, budesonide) twice daily—reduce mucosal inflammation and accelerate symptom resolution; supported by strong evidence from multiple randomized controlled trials. 1, 6
• Saline nasal irrigation 2–3 times daily—provides symptomatic relief and clears mucus. 1, 6
• Analgesics (acetaminophen or ibuprofen)—for pain and fever control. 1, 6
• Decongestants (oral or topical)—limit topical agents to ≤3 days to avoid rebound congestion. 1

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Watchful Waiting: When to Defer Antibiotics

For uncomplicated ABRS with reliable follow-up, initial observation without antibiotics is appropriate. 1

• Start antibiotics only if no improvement by day 7 or symptoms worsen at any time. 1
• Number needed to treat (NNT) with antibiotics is 10–15 to achieve one additional cure, reflecting high spontaneous recovery rates. 1
• Provide symptomatic treatment during observation period. 3, 6

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Monitoring and Reassessment Protocol

Reassess at 3–5 Days

• If no improvement: Switch to high-dose amoxicillin-clavulanate or a respiratory fluoroquinolone. 1
• If worsening at any time: Evaluate urgently for complications (orbital cellulitis, meningitis, intracranial abscess). 1

Reassess at 7 Days

• If symptoms persist or worsen: Reconfirm diagnosis, exclude complications, and consider imaging (CT) only when complications are suspected. 1
• By day 7,73–85% of patients show improvement even with placebo; lack of improvement suggests treatment failure or misdiagnosis. 1

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Critical 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—98–99.5% of acute rhinosinusitis is viral. 1, 3
• Purulent nasal discharge alone does not indicate bacterial infection—it reflects neutrophilic inflammation common to viral disease. 2
• Do not obtain routine imaging (X-ray or CT) for uncomplicated ABRS; up to 87% of viral URIs show sinus abnormalities on imaging, leading to unnecessary interventions. 1, 7
• Ensure adequate treatment duration (≥5 days for adults, ≥10 days for children) to prevent relapse. 1
• Do not use fluoroquinolones as first-line therapy in patients without documented β-lactam allergy—reserve them to prevent resistance development. 1

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When to Refer to Otolaryngology

Refer immediately if any of the following occur:

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