What is the first line treatment for acute sinusitis?

Acute Sinusitis: First-Line Treatment and Differential Diagnosis

First-Line Antibiotic Treatment

Amoxicillin 500 mg twice daily for 10-14 days is the first-line treatment for uncomplicated acute bacterial sinusitis in adults, with amoxicillin-clavulanate 875 mg/125 mg twice daily preferred when beta-lactamase-producing organisms are suspected or in patients with recent antibiotic exposure. 1, 2, 3

When to Initiate Antibiotics

Antibiotics should only be started when acute bacterial sinusitis is confirmed by one of three clinical patterns: 1, 2

• Persistent symptoms ≥10 days without improvement (purulent nasal discharge, facial pain, nasal congestion) 1, 2
• Severe symptoms for ≥3 consecutive days (fever >39°C, purulent discharge, severe facial pain) 1, 2
• "Double sickening" - worsening symptoms after initial improvement from a viral upper respiratory infection 1, 4

Critical pitfall: Most acute rhinosinusitis cases are viral and resolve spontaneously within 7 days without antibiotics. 1 Symptoms lasting fewer than 7 days are unlikely to represent bacterial infection. 1

Antibiotic Selection Algorithm

For uncomplicated cases without recent antibiotic use:

• Amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) for 10-14 days 1, 2, 3

For patients with recent antibiotic exposure or high local resistance:

• Amoxicillin-clavulanate 875 mg/125 mg twice daily for 7-10 days 3, 5, 6
• This provides coverage against beta-lactamase-producing H. influenzae and M. catarrhalis 3, 5

For penicillin-allergic patients:

• Second-generation cephalosporins: cefuroxime-axetil 1, 2, 5
• Third-generation cephalosporins: cefpodoxime-proxetil, cefdinir, or cefprozil 1, 2, 5
• The risk of cross-reactivity with cephalosporins in penicillin-allergic patients is negligible 2

Avoid azithromycin and macrolides due to 20-25% resistance rates against S. pneumoniae and H. influenzae. 2, 3

Treatment Duration

Standard therapy is 10-14 days, treating until symptom-free for 7 days. 1, 2, 3 Some cephalosporins (cefuroxime-axetil, cefpodoxime-proxetil) are effective in 5-day courses. 1, 5

Treatment Failure Protocol

If no improvement after 3-5 days: 1, 2, 3

• Switch to high-dose amoxicillin-clavulanate (90 mg/kg amoxicillin component with 6.4 mg/kg clavulanate, not exceeding 2 g every 12 hours) 1
• Alternative: respiratory fluoroquinolones (levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily) 1, 2, 3

Reserve fluoroquinolones for: 1, 2

• Treatment failures after first-line therapy
• Frontal, ethmoidal, or sphenoidal sinusitis (higher complication risk)
• Multi-drug resistant S. pneumoniae

Adjunctive Therapies

Recommended supportive measures: 1, 2, 3

• Intranasal corticosteroids as adjunct to antibiotics 1, 2, 3
• Analgesics (acetaminophen, NSAIDs) for pain relief 1
• Decongestants (systemic or topical) - limit topical use to ≤3 days to avoid rhinitis medicamentosa 5
• Saline nasal irrigation for symptomatic relief 2
• Short-term oral corticosteroids for acute hyperalgic sinusitis (severe pain) or marked mucosal edema 1, 2, 3

Comfort measures: adequate rest, hydration, warm facial packs, steamy showers, sleeping with head elevated 1

Differential Diagnosis

The following conditions must be distinguished from acute bacterial sinusitis: 1

Upper Respiratory Conditions

• Viral upper respiratory tract infection - most common mimic, symptoms <7 days, diffuse bilateral nasal symptoms 1
• Allergic rhinitis (AR) - seasonal pattern, clear rhinorrhea, sneezing, itching 1
• Non-allergic rhinitis (NAR) - perennial symptoms without allergic triggers 1

Structural/Anatomic Abnormalities

• Nasal polyps - bilateral nasal obstruction, anosmia 1
• Sinonasal tumors - unilateral symptoms, epistaxis, progressive obstruction 1
• Nasopharyngeal tumor - unilateral symptoms, cranial nerve involvement 1
• Enlarged or infected adenoids (in children) 1

Other Infectious Causes

• Dental infections - particularly for unilateral maxillary sinusitis with upper dental pain 1
• Granulomatous disease - chronic progressive symptoms 1

Clinical Features by Anatomic Site

Maxillary sinusitis (most common): 1

• Unilateral or bilateral infraorbital pain worsening when bending forward
• Pulsatile pain peaking in evening/night
• Purulent rhinorrhea (anterior and/or posterior)

Frontal sinusitis: 1

• Supraorbital headache
• Requires more aggressive therapy due to complication risk

Ethmoidal sinusitis: 1

• Filling of inner angle of eye
• Palpebral edema
• Retro-orbital headache

Sphenoidal sinusitis: 1

• Permanent retro-orbital headache radiating to vertex
• Purulent discharge on posterior pharyngeal wall
• May simulate intracranial hypertension

Red Flags Requiring Immediate Hospitalization

Signs of complicated sinusitis: 1

• Meningeal syndrome
• Exophthalmos
• Palpebral edema
• Ocular mobility disorders
• Severe pain preventing sleep

These require hospitalization, bacteriological testing, and parenteral antibiotic therapy. 1

Pediatric Considerations

Standard dosing: Amoxicillin 45 mg/kg/day in 2 divided doses 2, 3

High-dose therapy (for areas with resistant S. pneumoniae or risk factors): 2, 3

• Amoxicillin 80-90 mg/kg/day in 2 divided doses, OR
• Amoxicillin-clavulanate 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses

Risk factors requiring high-dose therapy: age <2 years, daycare attendance, recent antibiotic use 2

Follow-Up and Recurrent Disease

Patients should contact their physician if: 1

• Symptoms worsen (especially headache or high fever)
• No improvement within 3-5 days of treatment

For recurrent sinusitis (≥3 episodes per year): 1, 3

• Evaluate for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities
• Consider referral to allergist-immunologist or otolaryngologist