What is the recommended antibiotic treatment for a patient with a wet cough who is allergic to penicillin (penicillin)?

Antibiotic Treatment for Chronic Wet Cough in Penicillin-Allergic Patients

For children ≤14 years with chronic wet cough (>4 weeks) who are allergic to penicillin, macrolides (azithromycin or clarithromycin) are the recommended alternative antibiotics, targeting the common respiratory bacteria Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1

Treatment Algorithm

Initial Assessment

• Confirm the cough is truly "wet" (loose, rattling sound) and has persisted for >4 weeks 1
• Rule out specific cough pointers that would require immediate investigation: digital clubbing, coughing with feeding, failure to thrive, hemoptysis, chest wall deformity, or abnormal chest radiograph 1
• Verify penicillin allergy history, though formal allergy testing is not required before initiating alternative therapy 1

First-Line Alternative Antibiotic Selection

Azithromycin is the preferred macrolide due to superior activity against H. influenzae compared to other macrolides and convenient once-daily dosing 2, 3:

• Dosing: 10 mg/kg once daily for 3 days, OR 10 mg/kg on day 1, then 5 mg/kg daily for 4 days 4, 2
• Achieves high tissue and intracellular concentrations that persist for days after dosing 3
• Clinical cure rates of 85-89% for respiratory infections in pediatric patients 4

Clarithromycin is an acceptable alternative 1, 5:

• Dosing: 7.5 mg/kg twice daily for 10 days (maximum 500 mg per dose) 6
• Requires longer treatment duration than azithromycin 4
• Has more drug interactions due to cytochrome P-450 3A inhibition 7

Treatment Duration and Response Assessment

Initial 2-week course: 1

• If cough resolves within 2 weeks, diagnose as protracted bacterial bronchitis (PBB) 1
• Monitor for clinical improvement within 48-72 hours 8

If wet cough persists after 2 weeks: 1

• Prescribe an additional 2 weeks of the same appropriate antibiotic
• Total treatment duration should not exceed 4 weeks before pursuing further investigation

If wet cough persists after 4 weeks of antibiotics: 1

• Proceed to further investigations: flexible bronchoscopy with quantitative cultures, chest CT scan, or immunologic assessment 1
• This suggests possible underlying lung disease such as bronchiectasis 1

Important Clinical Considerations

Macrolide Resistance

• Macrolide resistance rates among respiratory pathogens in the United States are approximately 5-8% 7
• Despite resistance concerns, macrolides remain effective for most cases of PBB in penicillin-allergic patients 2, 5

Cephalosporin Use in Penicillin Allergy

Cephalosporins may be considered in select penicillin-allergic patients 1, 7:

• Safe to use: In patients with non-severe, delayed-type penicillin reactions that occurred >1 year ago, second- or third-generation cephalosporins (cefdinir, cefuroxime, cefpodoxime) have only 0.1% cross-reactivity 7
• Never use: In patients with immediate-type (anaphylactic) penicillin reactions due to up to 10% cross-reactivity risk 1, 7
• Avoid: In patients with severe delayed reactions like Stevens-Johnson syndrome 7

Common Pitfalls to Avoid

• Do not use fluoroquinolones as first-line therapy in children; they have unnecessarily broad spectrum and are expensive 1, 7
• Do not prescribe tetracyclines in children <8 years due to tooth discoloration risk and high gastrointestinal side effects 7, 5
• Do not use trimethoprim-sulfamethoxazole as it lacks adequate coverage against common respiratory pathogens 7
• Avoid erythromycin due to substantially higher gastrointestinal side effects compared to azithromycin or clarithromycin 7, 4

Adverse Effects

Macrolides are generally well-tolerated in children 4, 2:

• Most common side effects: diarrhea (3-6%), vomiting (2-6%), and abdominal pain (1-3%) 4, 2
• Azithromycin has lower gastrointestinal side effect rates than amoxicillin-clavulanate 4, 2
• Monitor for QT prolongation with clarithromycin, especially in patients on other QT-prolonging medications 7

Special Populations

Consider antibiotic resistance risk factors 8:

• Recent antibiotic use within the past month
• Failure of prior antibiotic therapy
• Contact with healthcare environments
• Immunocompromised status

These factors may warrant culture-directed therapy or alternative antibiotic selection 8