What antibiotic is effective for treating bronchitis and sinus infections?

Antibiotic Coverage for Bronchitis and Sinus Infection

For acute bacterial sinusitis, amoxicillin 500 mg twice daily (or 875 mg twice daily for more severe infections) for 10-14 days is the first-line antibiotic choice, providing effective coverage against the most common pathogens including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1

Critical Distinction: Most Bronchitis Does NOT Require Antibiotics

Acute bronchitis is predominantly viral (caused by adenovirus, rhinovirus, coronavirus, influenza, parainfluenza, respiratory syncytial virus), with only occasional cases due to M. pneumoniae, C. pneumoniae, or Legionella species. 2 The frequency of bacterial infection in acute bronchitis is uncertain, and most cases resolve without antibiotics. 2

• For acute exacerbations of chronic bronchitis (not simple acute bronchitis), antibiotics targeting S. pneumoniae, H. influenzae, and M. catarrhalis are appropriate when bacterial infection is suspected. 2

First-Line Treatment for Acute Bacterial Sinusitis

Amoxicillin remains the gold standard because it provides 70-80% clinical response rates and covers the three primary pathogens. 2

Standard Dosing:

• Adults: 500 mg twice daily for mild disease; 875 mg twice daily for moderate disease 1
• Children: 45 mg/kg/day in 2 divided doses (standard); 80-90 mg/kg/day in 2 divided doses for high-risk children (age <2 years, daycare attendance, recent antibiotic use, or areas with high resistant S. pneumoniae prevalence) 1
• Duration: 10-14 days or until symptom-free for 7 days 2, 1

Penicillin-Allergic Patients

For patients with documented penicillin allergy (non-anaphylactic reactions), second- or third-generation cephalosporins are safe and effective alternatives:

• Cefuroxime-axetil (second-generation) 2, 1
• Cefpodoxime-proxetil (third-generation, superior activity against H. influenzae) 2, 1
• Cefdinir (third-generation) 1

The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible, making these excellent alternatives. 1

Second-Line Treatment for Treatment Failure

If no improvement occurs after 3-5 days of amoxicillin, switch to high-dose amoxicillin-clavulanate (875 mg/125 mg twice daily for adults; 90 mg/kg/day amoxicillin component for children). 1 This provides coverage against β-lactamase-producing H. influenzae and M. catarrhalis (50-70% of M. catarrhalis strains produce β-lactamase). 2

For Severe Penicillin Allergy or Second-Line Failure:

Respiratory fluoroquinolones (levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 10 days) provide 90-92% predicted clinical efficacy and excellent coverage against drug-resistant S. pneumoniae. 1, 3 However, fluoroquinolones should be reserved for treatment failures or complicated sinusitis to prevent resistance development. 1

Antibiotics to AVOID

Azithromycin and other macrolides should NOT be used for acute bacterial sinusitis due to resistance rates of 20-25% for both S. pneumoniae and H. influenzae. 1 Despite FDA approval of clarithromycin for acute maxillary sinusitis 4, current guidelines explicitly exclude macrolides from recommended therapy due to resistance prevalence. 1

Doxycycline has a 20-25% predicted bacteriologic failure rate due to limited activity against H. influenzae and should only be considered when better alternatives are unavailable. 1

Adjunctive Therapies

Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) are strongly recommended as adjunctive therapy, as they reduce mucosal inflammation and improve symptom resolution. 1 Short-term oral corticosteroids may be reasonable for patients with marked mucosal edema or failure to respond to initial treatment. 1

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for viral rhinosinusitis: Wait at least 10 days unless severe symptoms are present (fever >39°C, purulent discharge, facial pain for ≥3 consecutive days). 1
• Reassess at 72 hours (pediatrics) or 3-5 days (adults): If no improvement, switch antibiotics rather than continuing ineffective therapy. 1
• Complete the full antibiotic course even after symptoms improve to prevent relapse. 1
• Avoid using fluoroquinolones as first-line therapy when other options are available, as this contributes to antimicrobial resistance. 3