What is the best antibiotic for acute bacterial sinusitis?

Best Antibiotic for Acute Bacterial Sinusitis

For most adults with acute bacterial sinusitis, amoxicillin with or without clavulanate is the first-line antibiotic, prescribed for 5 to 10 days. 1

Initial Antibiotic Selection

Standard First-Line Therapy

Amoxicillin alone (1.5-4 g/day) is appropriate for mild disease in patients without recent antibiotic use (past 4-6 weeks). 1 This provides 87-88% clinical efficacy and 91-92% bacteriologic efficacy against the primary pathogens Streptococcus pneumoniae and Haemophilus influenzae. 1

Amoxicillin-clavulanate (875 mg twice daily) should be chosen over amoxicillin alone when:

• Recent antibiotic use within the past 4-6 weeks 1
• Moderate to severe symptoms 1
• Age >65 years 1
• Diabetes or other chronic comorbidities 1
• Immunocompromised status 1
• High local prevalence (>10%) of penicillin-resistant S. pneumoniae 1
• Close contact with daycare children 1
• Smoking or household smoker 1

High-Dose Regimens

High-dose amoxicillin-clavulanate (4 g amoxicillin/250 mg clavulanate daily, given as 2 g twice daily) is recommended for patients at high risk of resistant organisms. 1 This formulation achieves 91% clinical efficacy and 99% bacteriologic efficacy. 1 However, a 2021 randomized trial found no additional benefit of high-dose over standard-dose formulations in adults, though this study was stopped early for futility. 2

Penicillin-Allergic Patients

For patients with true penicillin allergy (Type I hypersensitivity), respiratory fluoroquinolones are the preferred alternative. 1

Recommended alternatives include:

• Levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 5-10 days 1
• Doxycycline 100 mg twice daily (81% clinical efficacy, but lower bacteriologic efficacy at 80%) 1

For non-Type I reactions (e.g., rash), cephalosporins are acceptable:

• Cefpodoxime proxetil, cefuroxime axetil, or cefdinir 1
• These achieve 83-87% clinical efficacy 1

Macrolides (azithromycin, clarithromycin) should be avoided when possible due to limited effectiveness (77% clinical efficacy, 73% bacteriologic efficacy) and 20-25% bacterial failure rates. 1 Use only when no other options exist due to allergy. 1

Duration of Therapy

Treatment duration of 5-7 days is as effective as 10 days for most patients and causes fewer adverse effects. 1 The 2015 American Academy of Otolaryngology guidelines explicitly recommend discussing shorter courses with patients to reduce side effects. 1

Standard duration remains 10 days when:

• Severe infection is present 1
• Immunocompromised patients 1
• Frontal or sphenoidal sinusitis 3

Treatment Failure Management

If symptoms fail to improve after 72 hours or worsen at any time, reassess the patient and switch antibiotics. 1

Switching strategy:

• If started on amoxicillin → switch to respiratory fluoroquinolone (levofloxacin, moxifloxacin) or high-dose amoxicillin-clavulanate 1
• If started on amoxicillin-clavulanate → switch to respiratory fluoroquinolone or ceftriaxone 1 g IM/IV daily for 5 days 1
• If started on cephalosporin → switch to amoxicillin-clavulanate 4 g/250 mg or respiratory fluoroquinolone 1

After 7 days without improvement, reevaluate for:

• Misdiagnosis 1
• Complications (orbital involvement, intracranial extension) 3
• Need for imaging (CT scan) or endoscopy 1
• Sinus aspiration for culture 1

Common Pitfalls

Avoid prescribing fluoroquinolones as first-line therapy for uncomplicated cases to prevent promoting resistance, particularly of gut organisms. 1 Reserve these for treatment failures or true penicillin allergy. 1

Do not use rifampin as monotherapy or for longer than 10-14 days, as resistance emerges rapidly. 1

Recognize that watchful waiting without antibiotics is appropriate for uncomplicated cases with assured follow-up, as many patients improve spontaneously. 1 This reduces adverse events and antibiotic resistance. 1