What is the recommended treatment for pertussis?

Treatment of Pertussis

Azithromycin is the first-line antibiotic for treating pertussis across all age groups, with age-specific dosing: 10 mg/kg/day for 5 days in infants <6 months, and 10 mg/kg (max 500 mg) on day 1 followed by 5 mg/kg/day (max 250 mg) on days 2-5 for children ≥6 months and adults receiving 500 mg then 250 mg daily. 1

Age-Specific Antibiotic Regimens

Infants <6 Months

• Azithromycin 10 mg/kg/day for 5 consecutive days is the CDC-recommended first-line treatment, preferred over erythromycin due to significantly lower risk of infantile hypertrophic pyloric stenosis (IHPS) 2, 1
• Monitor all infants receiving macrolides for signs of IHPS (projectile vomiting, visible peristaltic waves, palpable olive-shaped mass), though risk with azithromycin is substantially lower than erythromycin 2
• Erythromycin should be avoided in this age group but if unavoidable, dose at 40-50 mg/kg/day divided in 4 doses for 14 days with mandatory IHPS monitoring 3, 4

Children ≥6 Months and Adolescents

• Azithromycin: 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg/day (maximum 250 mg) on days 2-5 1
• Clarithromycin is an acceptable alternative first-line option for children 1-5 months of age 1

Adults

• Azithromycin: 500 mg on day 1, followed by 250 mg daily on days 2-5 1

Alternative Antibiotic Options

• Trimethoprim-sulfamethoxazole (TMP-SMZ) is the recommended alternative for patients >2 months with macrolide contraindications or allergies 1
• Erythromycin remains an option when azithromycin is unavailable: 40-50 mg/kg/day (children) or 2 g/day (adults) in 4 divided doses for 14 days, though gastrointestinal side effects significantly limit compliance 3, 4, 5

Critical Timing Considerations

• Start antibiotics immediately upon clinical suspicion without waiting for culture confirmation, as early treatment during the catarrhal phase (first 2 weeks) rapidly clears B. pertussis from the nasopharynx and decreases coughing paroxysms 1
• Treatment initiated during the paroxysmal phase (>3 weeks) has limited clinical benefit for symptom control but remains indicated to prevent transmission 1
• Antibiotics eliminate the organism but do not alter the subsequent clinical course of paroxysmal coughing, post-tussive vomiting, or apnea once the paroxysmal phase has begun 2

Infection Control Measures

• Isolate patients at home and away from work/school for 5 days after starting antibiotics to prevent transmission 1
• All household contacts should receive prophylaxis with the same antibiotic regimen, especially critical when the household includes infants <12 months or women in the third trimester of pregnancy 2, 1
• Approximately 80-90% of untreated patients spontaneously clear B. pertussis within 3-4 weeks, but treatment prevents transmission to vulnerable individuals 2, 1

Important Medication Considerations

• Do not administer azithromycin simultaneously with aluminum- or magnesium-containing antacids, as they reduce absorption 2, 1
• Erythromycin and clarithromycin (but NOT azithromycin) inhibit cytochrome P450 enzymes and may interact with other medications metabolized by this system 1
• Erythromycin is contraindicated with astemizole, cisapride, pimazole, or terfenadine due to risk of QT prolongation and torsades de pointes 3

Supportive Care and What NOT to Do

• Do not use cough suppressants (dextromethorphan, codeine), corticosteroids, long-acting β-agonists, antihistamines, or pertussis immunoglobulin, as none have demonstrated benefit in controlling coughing paroxysms 2, 1
• Provide supportive care including positioning upright during coughing episodes, small frequent feedings to minimize post-tussive vomiting, and maintaining adequate hydration 2

Hospitalization Criteria for Infants

• Apneic episodes (breathing pauses >10-15 seconds), severe post-tussive vomiting causing dehydration, respiratory distress, oxygen desaturation <90-92%, or altered mental status are indications for immediate hospitalization 2
• Infants <6 months, especially <4 months, have the highest risk of severe and fatal complications; maintain a very low threshold for hospital admission 2

Expected Clinical Course

• Paroxysmal coughing persists for 6-10 weeks total (the "100-day cough") despite appropriate antibiotic therapy, as antibiotics only eliminate bacterial carriage 2
• The patient becomes non-infectious after 5 days of appropriate antibiotics but symptoms continue throughout the natural disease course 2