What are the recommended antibiotics for bacterial upper respiratory infections (URI)?

Recommended Antibiotics for Bacterial Upper Respiratory Infections

Amoxicillin is the first-line antibiotic treatment for confirmed bacterial upper respiratory infections, with a recommended dosage of 500mg three times daily or 875mg twice daily for adults. 1

Determining Bacterial vs. Viral Etiology

Before initiating antibiotics, it's crucial to determine if the URI is bacterial or viral:

• Most URIs are viral in origin and do not require antibiotics 2
• Bacterial infection is more likely when:
  • Symptoms persist for more than 10 days without improvement
  • Symptoms are severe (fever >39°C, purulent nasal discharge, facial pain for >3 consecutive days)
  • Symptoms worsen after initial improvement ("double sickening") 3
  • Fever persists for more than 3 days 3

First-Line Antibiotic Therapy

For confirmed bacterial URIs:

• Amoxicillin: 500mg three times daily or 875mg twice daily (1.5-4g/day total) 1, 4
  • Duration: 5-7 days for adults, 10-14 days for children 1
  • Target pathogens: Streptococcus species, Streptococcus pneumoniae, Haemophilus influenzae (β-lactamase negative) 4

Alternative First-Line Options (Penicillin Allergy)

For patients with penicillin allergy:

• Doxycycline: 100mg twice daily 5
• Macrolides: (e.g., azithromycin) though these have higher failure rates (20-25%) 1

Second-Line Antibiotic Therapy

For treatment failures, high-risk patients, or areas with high resistance rates:

• Amoxicillin-clavulanate: The reference second-line antibiotic 3, 1
• Second/third-generation cephalosporins:
  • Cefuroxime-axetil
  • Cefpodoxime-proxetil 3, 1
• Respiratory fluoroquinolones (reserved for treatment failures or high-risk situations):
  • Levofloxacin
  • Moxifloxacin 1

Specific Considerations by URI Type

Acute Rhinosinusitis

• Watchful waiting is recommended for uncomplicated cases 3
• If antibiotics needed, amoxicillin is first-line, with amoxicillin-clavulanate for treatment failures 3, 1
• Adjunctive therapy: intranasal saline irrigation, intranasal corticosteroids 3

Acute Otitis Media

• Amoxicillin-clavulanate is preferred 3

Exacerbation of Chronic Bronchitis

• Simple chronic bronchitis: Antibiotics only if fever persists >3 days 3
• Chronic obstructive bronchitis: Antibiotics if at least 2 of 3 Anthonisen criteria present (increased dyspnea, increased sputum purulence, increased sputum volume) 3, 1
• Chronic respiratory insufficiency: Immediate antibiotic therapy recommended 3

Monitoring and Follow-up

• Assess clinical response after 48-72 hours 1
• If symptoms worsen or fail to improve:
  • Consider alternative diagnosis
  • Switch to amoxicillin-clavulanate
  • Add coverage for atypical pathogens
  • Consider referral and imaging studies 1

Common Pitfalls to Avoid

• Prescribing antibiotics for viral URIs (most URIs are viral) 2, 6
• Using broad-spectrum antibiotics as first-line treatment 7
• Inadequate duration of therapy (complete the full course even if symptoms improve quickly) 1
• Using fluoroquinolones for uncomplicated cases (reserve for treatment failures) 3
• Using cotrimoxazole (poor activity against pneumococci and poor benefit/risk ratio) 3

Remember that judicious use of antibiotics is essential to prevent the emergence of resistant bacteria. Antibiotics should be prescribed only when there is strong clinical evidence of bacterial infection.