What is the best antibiotic for treating sinus infections?

Best Antibiotic for Sinus Infections

Amoxicillin-clavulanate (Augmentin) 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults. 1, 2

First-Line Treatment Selection

• Amoxicillin-clavulanate is preferred over plain amoxicillin due to increasing prevalence of beta-lactamase-producing organisms (H. influenzae and M. catarrhalis), which now represent a significant proportion of sinusitis pathogens. 2

• Plain amoxicillin (500 mg twice daily for mild infections, 875 mg twice daily for moderate infections) remains acceptable only for uncomplicated cases in patients without recent antibiotic exposure (within past 4-6 weeks). 1, 2

• The standard treatment duration is 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days (typically 7-10 days total). 1, 2

Treatment Based on Anatomic Location

• For maxillary sinusitis (the most common type, presenting with infraorbital pain worsening when bending forward): Use standard first-line antibiotics (amoxicillin-clavulanate). 1, 2

• For frontal, ethmoidal, or sphenoidal sinusitis: Reserve respiratory fluoroquinolones (levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily) due to higher risk of serious complications like meningitis or orbital cellulitis. 1, 2, 3

Penicillin-Allergic Patients

• Second-generation cephalosporins (cefuroxime-axetil) or third-generation cephalosporins (cefpodoxime-proxetil, cefdinir, cefprozil) are appropriate alternatives for documented penicillin allergy. 1, 2

• Recent evidence demonstrates the risk of serious cross-reactivity between penicillins and second/third-generation cephalosporins is negligible (<1%), making these safe alternatives. 1

• Avoid azithromycin and other macrolides as first-line therapy due to 20-25% resistance rates among S. pneumoniae and H. influenzae. 1, 3

Second-Line Treatment for Treatment Failure

• If no improvement within 3-5 days, switch to high-dose amoxicillin-clavulanate (if not already used) or consider respiratory fluoroquinolones. 1, 2

• Levofloxacin (500 mg once daily for 10-14 days or 750 mg once daily for 5 days) or moxifloxacin (400 mg once daily for 10 days) are second-line options with 90-92% predicted clinical efficacy and excellent coverage against multi-drug resistant S. pneumoniae (MDRSP). 1, 4

• Never use ciprofloxacin for sinusitis—it has inadequate coverage against S. pneumoniae (AUC-to-MIC ratio of only 10-20 vs. target of 25-30). 3

Adjunctive Therapies

• Intranasal corticosteroids should be used as an adjunct to antibiotic therapy in both acute and chronic sinusitis to reduce mucosal inflammation. 1, 2

• Short-term oral corticosteroids (e.g., dexamethasone 4 mg) may be considered for acute hyperalgic sinusitis (severe pain) or marked mucosal edema when patients fail initial treatment. 1, 2

Pediatric Dosing

• Standard therapy: Amoxicillin 45 mg/kg/day in 2 divided doses. 1

• High-dose therapy (for areas with high prevalence of resistant S. pneumoniae, age <2 years, daycare attendance, or recent antibiotic use): 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. 1, 2

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

Critical Pitfalls to Avoid

• Do not use fluoroquinolones as routine first-line therapy—reserve them for treatment failures, complicated sinusitis (frontal/ethmoidal/sphenoidal), or multi-drug resistant organisms to prevent resistance development. 1, 3

• Ensure adequate treatment duration (minimum 5 days, typically 7-10 days) to prevent relapse; some patients require treatment until symptom-free for 7 days. 1, 2

• Reassess at 3-5 days if no improvement to avoid treatment failure—this is when you should switch antibiotics, not wait longer. 1, 2

• Complete the full antibiotic course even after symptoms improve to prevent relapse and resistance development. 1

• Fluoroquinolones carry risks of Achilles tendon rupture and other serious adverse effects, particularly in patients with renal dysfunction—another reason to reserve them for second-line use. 3

Watchful Waiting Option

• For adults with uncomplicated acute bacterial sinusitis, watchful waiting without immediate antibiotics is appropriate when follow-up can be assured, with antibiotics started if no improvement by 7 days or worsening at any time. 1

• The number needed to treat with antibiotics for persistent symptoms is 3-5, meaning many cases resolve spontaneously. 1