What is the recommended antibiotic treatment for acute uncomplicated sinusitis?

Antibiotic Treatment for Acute Uncomplicated Sinusitis

For acute uncomplicated bacterial sinusitis in adults, amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic, with plain amoxicillin 500-875 mg twice daily reserved for patients without recent antibiotic exposure or risk factors for resistant organisms. 1, 2

When to Prescribe Antibiotics (Not All Sinusitis Needs Treatment)

Before prescribing any antibiotic, confirm the diagnosis meets one of three criteria for bacterial sinusitis:

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

Critical pitfall: 98-99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7-10 days without antibiotics. 1 Do not prescribe antibiotics for symptoms lasting <10 days unless severe symptoms are present. 1

First-Line Antibiotic Selection

Standard First-Line: Amoxicillin-Clavulanate

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is preferred over plain amoxicillin because 50% of Haemophilus influenzae and 90-100% of Moraxella catarrhalis produce β-lactamase, rendering plain amoxicillin ineffective against these organisms. 4, 1, 2

When Plain Amoxicillin Is Acceptable

Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable for:

• Uncomplicated cases without recent antibiotic exposure (within past 4-6 weeks) 1, 2
• Patients without risk factors for resistant organisms 1

High-Dose Regimen for Resistant Organisms

Use high-dose amoxicillin-clavulanate (2 g amoxicillin/125 mg clavulanate twice daily) for patients with: 1, 2

• Recent antibiotic use within past month
• Age >65 years
• Moderate-to-severe symptoms
• Comorbid conditions or immunocompromised state
• High local prevalence of penicillin-resistant Streptococcus pneumoniae (25-50% of strains) 4

Treatment Duration

Standard duration is 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days (typically 10-14 days total). 1, 2 Shorter 5-7 day courses have comparable efficacy with fewer side effects. 1, 5

Reassess at 3-5 days: If no improvement, switch antibiotics or re-evaluate the diagnosis. 1, 2

Penicillin-Allergic Patients

Non-Severe Allergy (Rash, Delayed Reactions)

Second-generation cephalosporins are first-line alternatives: 1, 2

• Cefuroxime-axetil 250-500 mg twice daily for 10 days

Third-generation cephalosporins provide superior activity against H. influenzae: 1, 2

• Cefpodoxime-proxetil 200-400 mg twice daily for 10 days
• Cefdinir 300 mg twice daily for 10 days

The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible (<1%). 1

Severe Allergy (Anaphylaxis/Type I Hypersensitivity)

Respiratory fluoroquinolones are the treatment of choice: 1, 6

• Levofloxacin 500 mg once daily for 10-14 days 1, 7
• Moxifloxacin 400 mg once daily for 10 days 1

These provide 90-92% predicted clinical efficacy against drug-resistant S. pneumoniae and β-lactamase-producing organisms. 1, 7

Critical pitfall: Do NOT use azithromycin or other macrolides—resistance rates exceed 20-25% for both S. pneumoniae and H. influenzae. 1 Do NOT use trimethoprim-sulfamethoxazole—50% resistance for S. pneumoniae. 1

Second-Line Treatment for Treatment Failure

If no improvement after 3-5 days of first-line therapy, switch to: 1, 2

High-dose amoxicillin-clavulanate (if not already used): 2 g amoxicillin/125 mg clavulanate twice daily for 10-14 days 1

OR

Respiratory fluoroquinolones: 1, 6

• Levofloxacin 500 mg once daily for 10-14 days
• Moxifloxacin 400 mg once daily for 10 days

Reserve fluoroquinolones for treatment failures, severe penicillin allergy, or complicated sinusitis (frontal, ethmoidal, sphenoidal involvement) to prevent resistance development. 1, 6

Adjunctive Therapies to Enhance Outcomes

Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) are strongly recommended as adjuncts to antibiotics—they reduce mucosal inflammation and improve symptom resolution. 1, 2

Short-term oral corticosteroids (typically 5 days) may be considered for: 1

• Patients with marked mucosal edema
• Failure to respond to initial antibiotic treatment
• Acute hyperalgic sinusitis (severe facial pain)

Supportive measures: 1

• Analgesics (acetaminophen, NSAIDs) for pain relief
• Saline nasal irrigation for symptomatic relief
• Adequate hydration
• Sleeping with head elevated

Watchful Waiting Option

For adults with uncomplicated acute bacterial sinusitis, watchful waiting without immediate antibiotics is appropriate when reliable follow-up can be assured. 1, 2 Instruct patients to start antibiotics only if no improvement by 7 days or if symptoms worsen at any time. 1

The number needed to treat with antibiotics is 10-15 to achieve one additional clinical cure, as 90% of patients improve naturally within 7-15 days. 1

Pediatric Dosing Considerations

Standard-dose amoxicillin: 45 mg/kg/day divided into 2 doses 1

High-dose amoxicillin: 80-90 mg/kg/day divided into 2 doses for: 1

• Age <2 years
• Daycare attendance
• Recent antibiotic use (within 4-6 weeks)
• High local prevalence of resistant S. pneumoniae

High-dose amoxicillin-clavulanate: 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses 1

For penicillin-allergic children: Cefpodoxime-proxetil 8 mg/kg/day in 2 doses 1

Reassess pediatric patients at 72 hours—if no improvement, switch to high-dose amoxicillin-clavulanate or consider complications. 1

When to Refer to a Specialist

Refer to otolaryngology or allergy/immunology for: 1

• Symptoms refractory to two courses of appropriate antibiotics
• Recurrent sinusitis (≥3 episodes per year)
• Suspected complications (orbital cellulitis, meningitis, brain abscess)
• Need for sinus aspiration/culture in immunocompromised patients
• Evaluation for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities

Critical Pitfalls to Avoid

• Never use first-generation cephalosporins (cephalexin, cefadroxil)—they have inadequate coverage against H. influenzae. 4, 1
• Never use ciprofloxacin—it has poor activity against S. pneumoniae (AUC:MIC ratio only 10-20 vs. target of 25-30). 6
• Never use clindamycin as monotherapy—it lacks activity against H. influenzae and M. catarrhalis. 1
• Never use doxycycline as first-line—it has 20-25% predicted bacteriologic failure rate and limited activity against H. influenzae. 1
• Do not continue ineffective therapy beyond 3-5 days—reassess and switch antibiotics if no improvement. 1, 2
• Do not use topical decongestants >3 days—risk of rhinitis medicamentosa. 2
• Complete the full antibiotic course even after symptoms improve to prevent relapse. 1