What is the recommended dose of amoxicillin (amoxicillin) for a 15-year-old male with a sinus infection and no known allergies to penicillin (penicillin)?

Amoxicillin Dosing for Sinus Infection in a 15-Year-Old Male

For a 15-year-old male with acute bacterial sinusitis and no penicillin allergy, prescribe amoxicillin 500 mg three times daily (every 8 hours) for 10-14 days, taken at the start of meals. 1, 2

Standard Dosing Approach

• Adolescents aged 12 years and older should receive adult dosing of amoxicillin for sinusitis. 1
• The recommended regimen is 500 mg orally three times daily (every 8 hours) for 10-14 days. 1, 2, 3
• An alternative dosing option is 875 mg twice daily (every 12 hours) for 10-14 days, which may improve adherence. 2, 3
• All doses should be taken at the start of a meal to minimize gastrointestinal side effects. 4

When to Consider High-Dose Therapy

• High-dose amoxicillin (80-90 mg/kg/day, maximum 2 grams per dose twice daily) should be considered if the patient has: 1

  • Recent antibiotic use within the past 30 days 1
  • Moderate to severe symptoms 1
  • Lives in an area with high prevalence (>10%) of penicillin-resistant Streptococcus pneumoniae 1
  • Attends daycare or similar settings 1

• For a 15-year-old, this would translate to approximately 875 mg twice daily in most cases, as weight-based dosing typically applies to younger children. 1

Treatment Duration and Response Assessment

• Continue treatment for a minimum of 10 days, or until the patient has been symptom-free for 7 days. 1, 3, 5
• Evaluate clinical response after 3-5 days of therapy. 2, 3
• If symptoms worsen or fail to improve by day 3-5, consider switching to amoxicillin-clavulanate (875 mg/125 mg twice daily) to cover β-lactamase-producing organisms. 1, 2

Critical Diagnostic Considerations

• Antibiotics are only indicated for bacterial sinusitis, not viral upper respiratory infections. 1, 2, 3
• Bacterial sinusitis is diagnosed by one of three presentations: 5
  • Persistent symptoms (nasal discharge or cough) for ≥10 days without improvement 1, 2
  • Severe symptoms (high fever ≥38°C and purulent discharge) for 3-4 consecutive days 1, 5
  • "Double sickening" - worsening after initial improvement 1, 2, 5

Alternative Options for Treatment Failure

• If no improvement occurs after 3-5 days on standard amoxicillin, switch to: 1
  • Amoxicillin-clavulanate 875 mg/125 mg twice daily (preferred for β-lactamase producers) 1
  • Cefdinir, cefpodoxime, or cefuroxime (second-generation cephalosporins with better coverage) 1, 6
  • Doxycycline 100 mg twice daily (alternative in penicillin allergy) 7

Penicillin Allergy Considerations

• For patients with non-severe penicillin allergy, second- or third-generation cephalosporins (cefdinir, cefpodoxime, cefuroxime) are safe, as cross-reactivity risk is minimal. 1, 6
• For severe penicillin allergy (anaphylaxis, Stevens-Johnson syndrome), use doxycycline 100 mg twice daily or a respiratory fluoroquinolone (levofloxacin 500 mg daily) in adults. 1, 7, 4

Common Pitfalls to Avoid

• Do not prescribe antibiotics for viral rhinosinusitis - studies show no benefit and increased adverse events. 1, 2, 3
• Do not use first-generation cephalosporins (cephalexin, cefadroxil) as they have poor coverage against H. influenzae. 1
• Do not use cefixime or ceftibuten - they have inadequate activity against S. pneumoniae, especially resistant strains. 1
• Failing to reassess at 3-5 days may delay necessary antibiotic changes and prolong illness. 2, 3
• Stopping antibiotics when symptoms improve (before completing 10 days or being symptom-free for 7 days) risks relapse. 3, 7, 5

Adjunctive Therapies

• Intranasal saline irrigation and intranasal corticosteroids are recommended as adjunctive treatments to improve symptom relief. 2
• Avoid oral decongestants and antihistamines - they provide no proven benefit in acute bacterial sinusitis. 2