What is the recommended dosage of amoxicillin for upper respiratory infections in adults?

Amoxicillin Dosage for Upper Respiratory Infections in Adults

For adults with upper respiratory infections, the recommended dosage of amoxicillin is 750 mg to 1750 mg per day, divided into doses every 8 to 12 hours, with 500 mg three times daily (1500 mg/day) being a standard regimen for mild disease. 1

Dosage Recommendations Based on Disease Severity

Mild Upper Respiratory Infections

• Standard dosage: 500 mg three times daily (1500 mg/day) 2
• Alternative regimen: 750 mg twice daily (1500 mg/day) 1
• Duration: Typically 7-10 days 2

Moderate to Severe Infections or Recent Antibiotic Use

• High-dose regimen: 1000 mg three times daily (3000 mg/day) 2
• Alternative: 1000 mg twice daily (2000 mg/day) 1
• For patients who have received antibiotics in the previous 4-6 weeks, higher doses are recommended due to increased risk of resistant organisms 2

Special Considerations

Bacterial Rhinosinusitis

• For mild disease: Amoxicillin 1.5 g/day (500 mg three times daily) 2
• For moderate disease or recent antibiotic use: High-dose amoxicillin 4 g/day (1000 mg four times daily) 2
• Consider amoxicillin/clavulanate if beta-lactamase-producing organisms are suspected 2

Penicillin-Resistant Streptococcus pneumoniae

• In areas with high prevalence of penicillin-resistant S. pneumoniae, high-dose amoxicillin (3-4 g/day) is recommended 2
• The British Thoracic Society doubled its recommended dosage of amoxicillin to 0.5-1 g every 8 hours in response to rising penicillin resistance 2

Monitoring and Treatment Failure

• Evaluate response to therapy after 72 hours 2
• Lack of response at 72 hours should prompt either:
  • Switch to alternative antimicrobial therapy
  • Reevaluation of the patient 2
• Consider respiratory fluoroquinolones or high-dose amoxicillin/clavulanate if treatment fails 2

Important Caveats

• Many upper respiratory infections are viral and do not require antibiotics 2
• Antibiotics should be used only for proven or strongly suspected bacterial infections to reduce development of resistant bacteria 1
• For patients with renal impairment (GFR >30 mL/min), dose reduction is necessary 1
• Common adverse effects include diarrhea, rash, vomiting, and nausea 1
• Higher dosages may increase cost and potential for adverse events, but these considerations are generally outweighed by the need to prevent treatment failure in areas with antibiotic resistance 2

Efficacy Considerations

• Amoxicillin has a predicted clinical efficacy of 83-88% for adults with acute bacterial rhinosinusitis 2
• High-dose amoxicillin (4 g/day) has a predicted clinical efficacy of 90-92% 2
• The spontaneous resolution rate in patients with a clinical diagnosis of acute bacterial rhinosinusitis is approximately 62% 2

Remember that the dosage should be adjusted based on local resistance patterns and the patient's recent antibiotic exposure history to maximize treatment success and minimize the development of resistance.