What is the recommended antibiotic for bacterial sinusitis?

Recommended Antibiotic for Bacterial Sinusitis

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic for adults with acute bacterial sinusitis, due to increasing prevalence of β-lactamase-producing organisms (H. influenzae and M. catarrhalis). 1

Confirm Bacterial Sinusitis Before Prescribing

Before initiating antibiotics, ensure the patient meets one of three diagnostic criteria 2, 1:

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

Critical caveat: 98-99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7-10 days without antibiotics—do not prescribe antibiotics for symptoms lasting <10 days unless severe features are present. 2

First-Line Antibiotic Selection

For Most Adults

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line choice over plain amoxicillin, given that 20-30% of H. influenzae and nearly 100% of M. catarrhalis produce β-lactamase. 1, 3 The clavulanate component provides essential coverage against these β-lactamase-producing organisms. 2

Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable only for uncomplicated cases without recent antibiotic exposure. 2

For Pediatric Patients

• Standard therapy: Amoxicillin 45 mg/kg/day in 2 divided doses for children without recent antibiotic use 2, 4
• High-risk children (age <2 years, daycare attendance, antibiotics within past 4-6 weeks, or high local resistance): High-dose amoxicillin-clavulanate 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses 2, 4

Treatment Duration

5-10 days of therapy is sufficient for most cases, with comparable efficacy to longer courses and fewer adverse effects. 2, 5 Most guidelines recommend treating until symptom-free for 7 days, typically totaling 10-14 days. 2

Penicillin-Allergic Patients

Non-Severe Allergy (Rash, Mild Reactions)

Second- or third-generation cephalosporins are safe and effective 2, 1:

• Cefuroxime-axetil (second-generation) 2
• Cefpodoxime-proxetil or cefdinir (third-generation, with superior activity against H. influenzae) 2, 3

The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible. 2

Severe Type I Hypersensitivity (Anaphylaxis)

Levofloxacin 500 mg once daily for 10-14 days or moxifloxacin 400 mg once daily for 10 days are appropriate alternatives, providing 90-92% predicted clinical efficacy. 2, 6

Critical pitfall: Azithromycin and other macrolides should NOT be used as first-line therapy due to resistance rates of 20-25% for both S. pneumoniae and H. influenzae. 2, 4

Second-Line Treatment for Treatment Failure

If no improvement occurs within 72 hours (pediatrics) or 3-5 days (adults), reassess the diagnosis and switch antibiotics 2, 1:

• High-dose amoxicillin-clavulanate (if not already used): 90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses for children; 2 g amoxicillin every 12 hours for adults 2
• Respiratory fluoroquinolones: Levofloxacin 500-750 mg once daily or moxifloxacin 400 mg once daily for 10-14 days, providing excellent coverage against drug-resistant S. pneumoniae and β-lactamase-producing organisms 2, 6
• Ceftriaxone: 1-2 g IM/IV once daily for 5 days (adults) or 50 mg/kg once daily (children) for patients unable to tolerate oral medications 2

Adjunctive Therapies

Intranasal corticosteroids (mometasone, fluticasone, or budesonide) twice daily should be added to antibiotic therapy in all patients, as they reduce mucosal inflammation and improve symptom resolution. 2, 1

Additional supportive measures include 2:

• Analgesics (acetaminophen, NSAIDs) for pain and fever
• Saline nasal irrigation for symptomatic relief
• Adequate hydration

Short-term oral corticosteroids may be considered for patients with marked mucosal edema or who fail to respond to initial treatment. 2

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for viral rhinosinusitis—wait at least 10 days unless severe symptoms are present 2, 1
• Do not use plain amoxicillin as first-line therapy given high prevalence (20-30%) of β-lactamase-producing organisms 1
• Do not continue ineffective antibiotics beyond 3-5 days—failure to reassess and switch therapy leads to prolonged illness and potential complications 2, 1
• Do not use azithromycin due to 20-25% resistance rates 2, 4
• Reserve fluoroquinolones for treatment failures or severe penicillin allergy to prevent resistance development 2, 1

Expected Timeline for Improvement

Most patients should experience noticeable improvement within 3-5 days of starting appropriate antibiotic therapy. 2 If no improvement occurs by this timepoint, reassess the diagnosis and consider switching antibiotics. 2, 1 Approximately 90% of patients improve naturally within 7-15 days, with or without antibiotics. 2