What antibiotics are recommended for treating bacterial sinusitis?

Antibiotic Treatment for Bacterial Sinusitis

For uncomplicated acute bacterial sinusitis in adults, amoxicillin-clavulanate is the preferred first-line antibiotic, while levofloxacin or moxifloxacin should be reserved for penicillin-allergic patients or treatment failures. 1, 2

First-Line Therapy for Adults

• High-dose amoxicillin-clavulanate is the preferred first-line agent for complicated sinusitis due to its effectiveness against common pathogens including resistant bacteria, S. pneumoniae, H. influenzae, and M. catarrhalis 1
• Treatment duration should be 10-14 days to ensure complete eradication of pathogens 1
• Nearly 100% of M. catarrhalis isolates are beta-lactamase positive and nonsusceptible to amoxicillin alone, making amoxicillin-clavulanate essential for coverage 2
• Plain amoxicillin should be avoided as it is ineffective against 90-100% of M. catarrhalis strains that produce beta-lactamase 2

First-Line Therapy for Children

• Standard-dose amoxicillin (45 mg/kg/day divided twice daily) is recommended for children aged ≥2 years with no recent antibiotic exposure, not attending daycare, and with mild-to-moderate disease 3, 4
• High-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day of clavulanate in 2 divided doses) is indicated for children with risk factors: age <2 years, daycare attendance, recent antibiotic use within 4 weeks, or high local prevalence of resistant S. pneumoniae 3, 4
• Treatment duration is 10-14 days total 4

Alternative Therapy for Penicillin-Allergic Patients

• For non-severe penicillin allergy, second or third-generation cephalosporins are appropriate: cefuroxime axetil, cefpodoxime, or cefdinir 1
• Recent evidence indicates the risk of serious allergic reactions to second- and third-generation cephalosporins in penicillin-allergic patients is almost nil 3
• For severe penicillin allergy (Type I hypersensitivity), respiratory fluoroquinolones are recommended: levofloxacin 500 mg once daily for 5-10 days or moxifloxacin 400 mg once daily for 5-10 days 1, 2, 5

Management of Treatment Failures

• Reassess at 72 hours - if symptoms worsen or fail to improve, change to second-line therapy 1, 4
• For children failing amoxicillin monotherapy, switch to high-dose amoxicillin-clavulanate 4
• For adults or children failing amoxicillin-clavulanate, respiratory fluoroquinolones (levofloxacin or moxifloxacin) have 90-92% predicted clinical efficacy and are the preferred second-line agents 1, 6
• The 72-hour threshold is evidence-based: only 9% of placebo-treated patients who failed at day 3 showed improvement between days 3-10 without intervention 4

Severe Cases Requiring Parenteral Therapy

• For children who are vomiting, unable to tolerate oral medication, or unlikely to be adherent, ceftriaxone 50 mg/kg IM/IV once daily can be used initially, then switch to oral therapy after improvement 3, 4
• For patients appearing acutely ill or toxic, consider inpatient therapy with IV cefotaxime or ceftriaxone 1
• For suspected orbital or intracranial complications, initiate IV vancomycin plus ceftriaxone or cefotaxime immediately and obtain urgent imaging and specialist consultation 4

What NOT to Use

• Plain amoxicillin should not be used even at high doses for M. catarrhalis infections, as beta-lactamase production cannot be overcome by dose escalation 2
• First-generation cephalosporins (cephalexin, cefadroxil) have poor coverage for M. catarrhalis and should be avoided 2
• Cefaclor has inadequate activity against beta-lactamase-producing M. catarrhalis and carries high risk of serum sickness-like reactions 2
• Azithromycin or clarithromycin have only 77-81% predicted clinical efficacy with bacterial failure rates of 20-25%, and should not be used as first-line therapy 2

Risk Factors Requiring High-Dose Therapy

• Age <2 years or >65 years 2
• Daycare attendance 3, 2
• Recent antibiotic use within 4-6 weeks 3, 2
• Diabetes or chronic comorbidities 2
• Immunocompromised status 2
• High local prevalence of resistant S. pneumoniae (>10%) 3

Special Considerations

• Nosocomial sinusitis is commonly caused by gram-negative bacilli, S. aureus, and anaerobes, requiring broader coverage 1
• Fungal sinusitis should be considered in immunocompromised patients and may require specific antifungal therapy and surgical debridement 1
• Intranasal corticosteroids can reduce inflammation and may provide additional benefit when used alongside antibiotics 1, 4
• Saline irrigation can improve mucociliary clearance 1

Critical Pitfalls to Avoid

• Do not reserve fluoroquinolones as first-line therapy for uncomplicated cases to prevent promoting resistance - use them only for treatment failures or true penicillin allergy 2
• Inadequate spectrum of antibiotic coverage for polymicrobial infections in complicated sinusitis leads to treatment failure 1
• Insufficient duration of therapy (less than 10-14 days) leads to incomplete eradication of pathogens 1
• Delayed recognition of treatment failure at 72 hours can lead to complications - reassessment is mandatory 1, 4