When to Use Amoxicillin
Amoxicillin should be used only for bacterial infections that are proven or strongly suspected to be caused by susceptible organisms, with specific indications including upper respiratory tract infections, genitourinary tract infections, skin and skin structure infections, and lower respiratory tract infections when appropriate clinical criteria are met.
Primary Indications for Amoxicillin
Amoxicillin is a penicillin-class antibacterial indicated for treatment of infections due to susceptible strains of designated microorganisms in the following conditions:
Upper Respiratory Tract Infections
- Acute Sinusitis: When symptoms persist >10 days without improvement or with severe symptoms 1
- Acute Otitis Media: Recommended for children with severe symptoms or in children <2 years 1
- Streptococcal Pharyngitis: For confirmed Group A Streptococcal infections
Lower Respiratory Tract Infections
- Community-Acquired Pneumonia: First-line for suspected pneumococcal pneumonia
- COPD Exacerbations: First-choice antibiotic when treatment is indicated 2
Other Indications
- Genitourinary Tract Infections: For susceptible organisms
- Skin and Skin Structure Infections: For susceptible organisms
- H. pylori Infection (adults only): As part of combination therapy 3
When NOT to Use Amoxicillin
- Lower Urinary Tract Infections: Amoxicillin is no longer recommended due to high resistance rates (75% of E. coli urinary isolates resistant) 2
- Viral Respiratory Infections: Most upper respiratory infections are viral and self-limiting 1
- Bronchiolitis: First-line antibiotic therapy is of no value due to low risk of invasive bacterial infection 2
Choosing Between Amoxicillin and Amoxicillin-Clavulanate
Use Amoxicillin When:
- Treating confirmed or suspected pneumococcal infections
- First-line therapy for most respiratory infections in patients without risk factors
- No recent antibiotic exposure (within 4-6 weeks)
Switch to Amoxicillin-Clavulanate When:
- Treatment failures with amoxicillin
- Recent antibiotic exposure
- Areas with high prevalence of β-lactamase-producing H. influenzae
- Severe symptoms or high risk of complications 1
- Young children with insufficient vaccination against H. influenzae type b 2
Dosing Considerations
Adults:
- Standard dose: 750-1750 mg/day in divided doses every 8-12 hours 3
- H. pylori infection: 1g twice daily (with clarithromycin and lansoprazole) or 1g three times daily (with lansoprazole) for 14 days 3
Children:
- 20-45 mg/kg/day in divided doses every 8-12 hours 3
- For pneumonia: 80-100 mg/kg/day in three daily doses for children <30 kg 2
- For neonates and infants ≤3 months: Maximum 30 mg/kg/day divided every 12 hours 3
Treatment Duration
- Respiratory infections: 5-7 days for adults, 10 days for pneumococcal pneumonia 1
- Atypical pneumonia: At least 14 days (with macrolides) 2
Common Pitfalls to Avoid
- Prescribing for viral infections: Most upper respiratory infections are viral and do not require antibiotics
- Using in high-resistance settings: Consider local resistance patterns before prescribing
- Failure to adjust for renal impairment: Reduce dose in patients with severe renal impairment (GFR >30 mL/min) 3
- Not considering allergies: Avoid in patients with history of serious hypersensitivity reactions to penicillins or other beta-lactams 3
Monitoring Response
- Clinical improvement should be evident within 48-72 hours of starting appropriate therapy
- If symptoms worsen or fail to improve, consider alternative diagnosis, imaging, or specialist referral 1
- Watch for adverse reactions including diarrhea, rash, vomiting, and nausea 3
- Monitor for serious reactions including anaphylaxis and Clostridioides difficile-associated diarrhea 3
By following these guidelines, amoxicillin can be used effectively while minimizing unnecessary antibiotic use and reducing the development of antibiotic resistance.