Antibiotic Choice for 17-Year-Old with Acute Airspace Disease/Possible Pneumonia
For a 17-year-old with acute airspace disease/possible pneumonia, oral amoxicillin 90 mg/kg/day in 2 divided doses (maximum 4 g/day) is the first-line antibiotic of choice, with the addition of a macrolide (azithromycin 500 mg day 1, then 250 mg days 2-5) if atypical pathogens cannot be clinically excluded. 1
Age-Based Treatment Algorithm
For Patients ≥5 Years Old (Including 17-Year-Olds)
Primary consideration: At age 17, both typical bacterial pathogens (Streptococcus pneumoniae) and atypical organisms (Mycoplasma pneumoniae, Chlamydophila pneumoniae) are common causes of community-acquired pneumonia. 1
Treatment decision pathway:
If clinical/radiographic features suggest typical bacterial pneumonia (lobar consolidation, high fever, productive cough): Start amoxicillin 90 mg/kg/day divided twice daily, maximum 4 g/day 1
If features are indeterminate or suggest atypical pneumonia (gradual onset, dry cough, patchy infiltrates): Add azithromycin 10 mg/kg day 1 (max 500 mg), then 5 mg/kg days 2-5 (max 250 mg) to the β-lactam regimen 1
If atypical pneumonia is strongly suspected: Macrolide monotherapy (azithromycin as above) is reasonable for outpatient management 1
Outpatient vs. Inpatient Considerations
Outpatient Management
- Oral amoxicillin remains first-line for presumed bacterial pneumonia 1
- Macrolide addition or monotherapy appropriate when atypical pathogens cannot be excluded 1
- Alternative to amoxicillin: amoxicillin-clavulanate (amoxicillin component 90 mg/kg/day in 2 doses, max 4000 mg/day) 1
Inpatient Management (If Hospitalization Required)
For fully immunized patients with minimal local penicillin resistance:
- Intravenous ampicillin or penicillin G 1
- Alternatives: ceftriaxone or cefotaxime 1
- Add azithromycin if atypical pneumonia diagnosis uncertain 1
For inadequate immunization or significant local penicillin resistance:
Special Considerations for Adolescents
Doxycycline option: For patients >7 years old (including 17-year-olds), doxycycline 2-4 mg/kg/day in 2 divided doses is an acceptable alternative to macrolides for atypical coverage 1
Fluoroquinolone consideration: Levofloxacin may be used for adolescents who have reached skeletal maturity or cannot tolerate macrolides, though this should be reserved for specific circumstances given antimicrobial stewardship concerns 1
Critical Pitfalls to Avoid
Do not use macrolide monotherapy if S. pneumoniae is likely: Amoxicillin must be the foundation when typical bacterial pneumonia is suspected, as macrolide resistance in pneumococcus exists and penicillin has no documented resistance 1, 2
Assess severity accurately: If the patient appears toxic, has respiratory distress, oxygen saturation ≤92%, or cannot tolerate oral intake, hospitalization with parenteral antibiotics is mandatory 1
Consider MRSA coverage: Add vancomycin or clindamycin only if clinical features suggest community-associated MRSA (necrotizing pneumonia, empyema, severe illness, recent influenza) 1
Vaccination status matters: Verify immunization against Haemophilus influenzae type b and S. pneumoniae—incomplete vaccination broadens the differential and may require broader-spectrum coverage 1
Treatment Duration
- Typical bacterial pneumonia: 10 days of β-lactam therapy 1
- Atypical pneumonia: 5 days of azithromycin (or 7-14 days of other macrolides) 1
- Combination therapy: Complete both courses as indicated 1
Evidence Quality Note
The PIDS/IDSA 2011 guidelines provide the most comprehensive, high-quality evidence for pediatric pneumonia management in this age group, with strong recommendations based on moderate-to-high quality evidence. 1 These guidelines appropriately recognize that 17-year-olds fall into the ≥5 years category where both typical and atypical pathogens must be considered, distinguishing this age group from younger children where S. pneumoniae predominates. 1