What is the recommended treatment for an infant diagnosed with pertussis?

Treatment for Infant with Pertussis

Azithromycin is the preferred first-line treatment for infants with pertussis, with dosing based on age: 10 mg/kg per day for 5 days in infants <6 months, and 10 mg/kg (maximum 500 mg) on day 1 followed by 5 mg/kg per day (maximum 250 mg) on days 2-5 for infants ≥6 months. 1

Age-Specific Treatment Recommendations

Infants <1 month of age:

• Azithromycin is the preferred macrolide at a dose of 10 mg/kg per day for 5 days 2, 1
• Azithromycin has fewer adverse events compared to erythromycin and has not been associated with infantile hypertrophic pyloric stenosis (IHPS) in this age group 2, 1
• Monitor for IHPS and other serious adverse events despite the lower risk 2

Infants 1-5 months of age:

• Azithromycin (10 mg/kg per day for 5 days) is recommended as first-line therapy 2, 1
• Clarithromycin can be considered as an alternative based on similar microbiologic effectiveness 2
• Both azithromycin and clarithromycin are preferred over erythromycin due to more convenient dosing schedule and better tolerability 1

Infants ≥6 months:

• Azithromycin: 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg per day (maximum 250 mg) on days 2-5 2, 1

Rationale for Macrolide Selection

• Azithromycin is preferred due to:

  • Better safety profile with fewer gastrointestinal side effects than erythromycin 2, 1
  • Significantly lower risk of infantile hypertrophic pyloric stenosis compared to erythromycin 1
  • More convenient once-daily dosing for 5 days (versus 14 days for erythromycin) 1
  • Similar microbiologic effectiveness against B. pertussis 2, 3

• Erythromycin has been associated with a 5-10% risk of IHPS in infants, with risk increasing with longer treatment duration 4

Important Treatment Considerations

• Early antibiotic administration can reduce duration and severity of symptoms and decrease the period of communicability 1

• Untreated infants with pertussis remain culture-positive for longer periods than older children and adults 2

• Monitor for potential side effects:

  • Azithromycin: abdominal discomfort, diarrhea, nausea, vomiting, headache, dizziness 2
  • Do not administer azithromycin simultaneously with aluminum- or magnesium-containing antacids as they reduce absorption 2, 1
  • Use azithromycin with caution in patients with impaired hepatic function 2

• Monitor for drug interactions, particularly with agents metabolized by cytochrome P450 enzyme system (e.g., digoxin, triazolam, ergot alkaloids) 2, 1

Special Considerations

• Pertussis is particularly dangerous in young infants, who account for most hospitalizations and deaths 5
• Early diagnosis and treatment with a macrolide before the paroxysmal stage can help mitigate complications and reduce spread 6
• If macrolides are contraindicated in infants >2 months of age, trimethoprim-sulfamethoxazole (TMP-SMZ) can be considered as an alternative 1
• Household contacts of pertussis patients should receive prophylaxis with the same antimicrobial agents and dosing regimens as for treatment 2, 7

Monitoring

• Infants <1 month who receive macrolides should be monitored for IHPS and other serious adverse events 2
• Watch for signs of IHPS including non-bilious vomiting or irritability with feeding 4
• Parents should be informed to contact their physician if vomiting or irritability with feeding occurs 4