What medicine is used to treat a respiratory infection?

Treatment of Respiratory Tract Infections

For community-acquired lower respiratory tract infections managed at home, aminopenicillin (amoxicillin) is the first-line antibiotic choice, with treatment typically lasting 5-7 days. 1

Key Principle: Not All Respiratory Infections Require Antibiotics

• Many respiratory infections are viral and self-limiting, making antibiotic therapy unnecessary and potentially harmful 1, 2
• Antibiotics should only be used when bacterial infection is present or strongly suspected based on clinical features 1
• Common cold, influenza, COVID-19, laryngitis, and acute bronchitis typically do NOT require antibiotics 2, 3

Antibiotic Selection by Clinical Setting

Outpatient/Home Management

First-line choice:

• Amoxicillin 500-1000 mg every 8 hours for 5-7 days 1, 4

Alternative options when first-line fails or specific circumstances exist:

• Amoxicillin-clavulanate (for areas with high beta-lactamase-producing H. influenzae, chronic lung disease, or recent aminopenicillin failure) 1, 4
• Macrolides (azithromycin, clarithromycin) for suspected atypical pathogens (Mycoplasma, Chlamydia) in young adults 1
• Tetracycline or doxycycline as alternatives, particularly for penicillin allergy 1
• Oral cephalosporins (cefuroxime-axetil) 1

Critical caveat: Patients must return if fever persists beyond 48 hours, as this suggests treatment failure or incorrect diagnosis 1

Hospital Management (Non-ICU)

For community-acquired pneumonia:

• Second or third-generation cephalosporins (ceftriaxone 1g IV every 24h or cefotaxime 1g IV every 8h) 1
• Add a macrolide (erythromycin 1g IV every 8h) to cover atypical pathogens 1
• Benzyl penicillin or IV amoxicillin in areas with low beta-lactamase-producing organisms 1

Switch to oral therapy at day 3 if patient is clinically stable 5

ICU/Severe Infections

• Third-generation cephalosporins PLUS macrolide or fluoroquinolone (levofloxacin, moxifloxacin) 1
• For suspected Pseudomonas: ciprofloxacin (reserved specifically for this indication) 1
• For aspiration pneumonia: amoxicillin-clavulanate 2g IV every 6h 1

Specific Clinical Scenarios

Chronic Bronchitis Exacerbations

Simple chronic bronchitis:

• Do NOT give immediate antibiotics, even with fever present 1
• Reassess at 2-3 days; only treat if fever >38°C persists beyond 3 days 1

Chronic obstructive bronchitis (FEV1 35-80%):

• Treat immediately only if at least 2 of 3 Anthonisen criteria present: increased dyspnea, increased sputum volume, increased sputum purulence 1

Severe COPD with respiratory insufficiency (FEV1 <35%):

• Immediate antibiotic therapy recommended 1
• Use second-line agents: amoxicillin-clavulanate, cefuroxime-axetil, or respiratory fluoroquinolones 1

Target Pathogens

The primary bacterial pathogens requiring coverage are:

• Streptococcus pneumoniae 1, 6
• Haemophilus influenzae 1, 6
• Moraxella catarrhalis 1, 6
• Atypical organisms (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella) 1

Treatment Duration

• Standard duration: 5-7 days for uncomplicated infections with favorable clinical response 1, 7, 5
• 7-10 days for pneumococcal pneumonia 1, 5
• Extended duration (10-14 days) for Mycoplasma or Chlamydophila 5
• 21 days for Legionella or Staphylococcus aureus pneumonia 5

Resistance Considerations

Critical resistance patterns affecting treatment:

• Macrolide resistance in S. pneumoniae (MIC >0.5 mg/L) predicts clinical failure in many countries 1
• Adequate beta-lactam dosing remains effective for penicillin-resistant pneumococci in extrameningeal infections 1
• Avoid fluoroquinolones if patient had recent FQ exposure, as this increases resistance risk 1
• Cotrimoxazole is NOT recommended due to inconsistent pneumococcal activity 1

Common Pitfalls to Avoid

• Do not treat viral infections with antibiotics - this includes most cases of acute bronchitis 2, 3
• Do not use oral cephalosporins for pneumococci with penicillin MIC >2 mg/L 1
• Do not extend treatment beyond 7-10 days in patients responding appropriately 5
• Do not use macrolides alone for H. influenzae (>98% have efflux pump resistance) 1
• Reassess at 48-72 hours - failure to improve mandates culture-directed therapy change 7