What is the recommended treatment for Bordetella pertussis (whooping cough)?

Treatment of Bordetella Pertussis (Whooping Cough)

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 patients ≥6 months. 1

Immediate Management Approach

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 and complications. 1 Late treatment (>3 weeks into illness) has limited clinical benefit for symptom control but remains indicated to prevent transmission to others. 1

Isolation Requirements

• Isolate the patient at home and away from work/school for 5 days after starting antibiotics to prevent transmission to vulnerable individuals, particularly infants and pregnant women. 1

Age-Specific Antibiotic Regimens

Infants <1 Month

• Azithromycin 10 mg/kg/day for 5 days is the preferred agent due to significantly lower risk of infantile hypertrophic pyloric stenosis (IHPS) compared to erythromycin. 1, 2
• Erythromycin is contraindicated in this age group due to IHPS risk; if absolutely necessary, use 40-50 mg/kg/day divided in 4 doses for 14 days with close monitoring. 1

Infants 1-5 Months

• Azithromycin 10 mg/kg/day for 5 days (first-line) 1, 2
• Clarithromycin 15 mg/kg/day divided twice daily for 7 days (alternative) 1

Infants ≥6 Months, Children, 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, 2
• Clarithromycin 15 mg/kg/day divided twice daily for 7 days (alternative) 1

Adults

• Azithromycin 500 mg on day 1, then 250 mg daily on days 2-5 1
• Clarithromycin 500 mg twice daily for 7 days (alternative) 1

Alternative Agent for Macrolide Contraindications

• Trimethoprim-sulfamethoxazole (TMP-SMZ) is recommended for patients >2 months with macrolide hypersensitivity or contraindications. 1
• Macrolides are absolutely contraindicated in patients with history of hypersensitivity to any macrolide agent. 1

Comparative Efficacy Evidence

Azithromycin and clarithromycin demonstrate equivalent microbiologic eradication rates to erythromycin (94-100% bacterial clearance), but with superior tolerability profiles. 1, 3 The shorter treatment duration (5-7 days vs. 14 days) significantly improves compliance while maintaining equal efficacy. 4, 3 Erythromycin resistance remains rare (<1%). 1

Critical Drug Interactions and Precautions

• Do not administer azithromycin with aluminum- or magnesium-containing antacids as they reduce absorption. 1
• Erythromycin and clarithromycin (but NOT azithromycin) inhibit cytochrome P450 enzymes and interact with digoxin, triazolam, and ergot alkaloids. 1
• Use caution in patients with impaired hepatic function. 1

Ineffective Therapies to Avoid

Do not use β-agonists, antihistamines, corticosteroids, or pertussis immunoglobulin as these have no proven benefit in controlling coughing paroxysms. 1 These agents are commonly prescribed but lack evidence for efficacy in pertussis management.

Post-Exposure Prophylaxis

The same antimicrobial agents and dosing regimens used for treatment apply to post-exposure prophylaxis. 1, 5

Priority Groups for Prophylaxis

• All household contacts regardless of vaccination status 2, 5
• Infants <12 months (especially <4 months) due to high risk of severe disease and mortality 2, 5
• Women in third trimester of pregnancy 1, 5
• Administer prophylaxis within 21 days of exposure for effectiveness 5

Rationale for Universal Household Prophylaxis

Pertussis has a secondary attack rate exceeding 80% among susceptible household contacts, and patients are most infectious during the catarrhal stage and first 3 weeks after cough onset. 5 Creating a protective "cocoon" around vulnerable infants through simultaneous prophylaxis of all household members is critical. 2

Common Pitfalls

• Waiting for culture confirmation before starting treatment: This delays therapy during the critical early phase when antibiotics are most effective at reducing symptoms and transmission. 1
• Using erythromycin in young infants: The IHPS risk makes this dangerous; always choose azithromycin instead. 1, 2
• Stopping isolation before 5 days of antibiotics: Patients remain contagious until completing 5 days of appropriate antibiotic therapy. 1
• Assuming vaccination provides lifelong immunity: Vaccine immunity wanes after 5-10 years, making previously vaccinated individuals susceptible. 5