What is the best antibiotic (abx) for sinusitis?

Best Antibiotic for Sinusitis

Amoxicillin with or without clavulanate is the first-line antibiotic for acute bacterial sinusitis in most adults, dosed at 500 mg twice daily for uncomplicated cases or 875 mg twice daily for more severe infections, for 5-10 days. 1, 2

First-Line Treatment Selection

For uncomplicated maxillary sinusitis (the most common type):

• Amoxicillin 500 mg twice daily is the standard first-line choice 1, 2
• Amoxicillin-clavulanate 875/125 mg twice daily provides broader coverage against beta-lactamase-producing organisms and is preferred when initial therapy fails or in areas with high resistance 1, 2
• Treatment duration is 5-10 days for most cases 1, 2

The 2015 American Academy of Otolaryngology guideline emphasizes that amoxicillin with or without clavulanate offers comparable efficacy to broader-spectrum antibiotics while reducing resistance and costs. 1 Recent research confirms that high-dose amoxicillin (1750 mg twice daily) does not provide additional benefit over standard dosing and increases severe diarrhea risk. 3, 4

Alternative First-Line Options for Penicillin Allergy

If penicillin-allergic:

• Cefuroxime 250-500 mg twice daily 1, 2
• Cefpodoxime 200-400 mg twice daily 1, 2
• Cefdinir (dosing per standard protocols) 2
• Pristinamycin specifically for beta-lactam allergy 1, 2

Important caveat: Azithromycin and other macrolides should NOT be used due to high resistance rates among Streptococcus pneumoniae and Haemophilus influenzae. 2

Treatment Based on Sinusitis Location

For frontal, ethmoidal, or sphenoidal sinusitis (more serious locations with higher complication risk):

• Fluoroquinolones are preferred: levofloxacin 500 mg daily or moxifloxacin 400 mg daily 1, 2, 5
• These should be reserved for complicated cases or first-line treatment failure in maxillary sinusitis 1, 2
• Levofloxacin can be given as 750 mg daily for 5 days as an alternative regimen 5

The French guidelines specifically recommend fluoroquinolones for frontal, fronto-ethmoidal, and sphenoidal sinusitis due to the risk of major complications like meningitis or orbital involvement. 1

When to Switch Antibiotics

If no improvement after 3-5 days:

• Switch to amoxicillin-clavulanate if started on amoxicillin alone 2
• Switch to a respiratory fluoroquinolone (levofloxacin or moxifloxacin) if already on amoxicillin-clavulanate 1, 2
• Consider obtaining cultures or imaging before switching 2

Adjunctive Therapies

Intranasal corticosteroids are recommended as adjuncts to antibiotics for symptom relief, though the benefit is modest (number needed to treat = 14). 1, 2

Short-term oral corticosteroids (e.g., dexamethasone 4 mg) may be added for acute hyperalgic sinusitis (severe pain) or marked mucosal edema, but only as adjunctive therapy with antibiotics, never as monotherapy. 1, 2

Critical Pitfalls to Avoid

• Do not use azithromycin or clarithromycin as first-line therapy due to resistance 2
• Do not prescribe antibiotics for viral upper respiratory infections lasting <10 days without bacterial features 1
• Do not use first-generation cephalosporins (cephalexin, cefadroxil) as they lack adequate coverage for H. influenzae 1
• Do not use high-dose amoxicillin regimens (>875 mg twice daily) as they increase adverse effects without improving outcomes 3, 4

Special Populations

For children:

• Amoxicillin 45 mg/kg/day in 2 divided doses (standard) or 80-90 mg/kg/day (high-resistance areas) 2
• Amoxicillin-clavulanate 80-90 mg/kg/day (amoxicillin component) for children <2 years, daycare attendance, or recent antibiotic use 2