When should antibiotics (abx) be prescribed for acute bacterial sinusitis?

When to Prescribe Antibiotics for Sinusitis

Antibiotics should be prescribed for acute bacterial sinusitis when patients present with one of three specific clinical patterns: persistent symptoms lasting ≥10 days without improvement, severe symptoms (fever ≥39°C with purulent nasal discharge for ≥3 consecutive days), or "double-sickening" (worsening after initial improvement from a viral URI). 1

Diagnostic Criteria for Antibiotic Initiation

The decision to prescribe antibiotics hinges on recognizing these three distinct presentations:

1. Persistent Symptoms (Most Common)

• Nasal discharge or daytime cough lasting more than 10 days without any clinical improvement 2, 1
• This is the most frequent presentation requiring antibiotics, as most viral rhinosinusitis resolves within 7-10 days 3, 4

2. Severe Onset

• Concomitant fever of at least 102.2°F (39°C) AND purulent nasal discharge for at least 3 consecutive days 2, 1
• Unilateral facial pain or pressure with purulent discharge also suggests bacterial infection 3, 4

3. Worsening Course ("Double-Sickening")

• Initial improvement from viral URI symptoms followed by worsening or new onset of nasal discharge, daytime cough, or fever 2, 1
• This pattern suggests secondary bacterial superinfection 5

Watchful Waiting as an Alternative Strategy

For patients with persistent but mild-to-moderate symptoms, watchful waiting for up to 7 days after diagnosis is an appropriate initial approach, delaying antibiotics while providing symptomatic treatment only. 1

• This strategy reduces unnecessary antibiotic use, adverse events, and bacterial resistance 1
• Most acute bacterial rhinosinusitis cases resolve spontaneously, with antibiotics benefiting only 1 in 10-15 patients compared to placebo 1
• Cure or improvement rates at 7-15 days are 91% with antibiotics versus 86% with placebo 1
• Watchful waiting requires assured patient follow-up 1

When to Start Antibiotics After Watchful Waiting

• Begin antibiotics if no improvement occurs after 7 days of observation 1
• Start antibiotics immediately if symptoms worsen at any time during observation 1

Critical Pitfalls to Avoid

Do NOT Prescribe Antibiotics When:

• Symptoms have lasted less than 10 days without severe features 1, 3
• The presentation is consistent with viral rhinosinusitis (98-99.5% of acute rhinosinusitis cases) 6, 3
• Mucus color alone is used to determine bacterial infection—color reflects neutrophils, not bacteria 1

Do NOT Use Imaging Routinely

• Plain radiography, CT, or MRI should not be performed to differentiate bacterial from viral sinusitis 2
• Imaging is reserved for suspected orbital or CNS complications (proptosis, impaired extraocular movements, severe headache, photophobia, seizures, focal neurologic findings) 2

First-Line Antibiotic Selection

When antibiotics are indicated:

• Amoxicillin alone (500-875 mg twice daily) or amoxicillin-clavulanate (875 mg/125 mg twice daily) for 5-10 days 1, 6
• For mild disease without recent antibiotic use: standard-dose amoxicillin (1.5-4 g/day) 1
• For risk factors (recent antibiotics, age <2 years, daycare attendance): high-dose amoxicillin-clavulanate (4 g/250 mg per day) 1

Penicillin-Allergic Patients

• Second- or third-generation cephalosporins (cefuroxime, cefpodoxime, cefdinir) 2, 1
• Respiratory fluoroquinolones (levofloxacin, moxifloxacin) reserved for severe allergy or treatment failure 1
• Do NOT use azithromycin or trimethoprim-sulfamethoxazole due to resistance rates of 20-25% 2, 1

Adjunctive Symptomatic Treatment During Observation

• Acetaminophen or ibuprofen for pain and fever 1
• Saline nasal irrigation for symptomatic relief 1, 3
• Nasal decongestants (limit topical use to 3 days to avoid rebound congestion) 1
• Intranasal corticosteroids (require at least 15 days of use for benefit) 1

Reassessment Timeline

• Evaluate patients at 3-5 days after starting antibiotics 1, 7
• If no improvement after 72 hours (pediatrics) or 3-5 days (adults), switch to second-line antibiotics or re-evaluate diagnosis 1, 7
• Consider complications, alternative diagnosis, or otolaryngology referral if symptoms worsen or fail to improve 7