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

Treatment of Whooping Cough (Pertussis)

Azithromycin is the first-line antibiotic for treating pertussis across all age groups, with a 5-day course being as effective as 14 days of erythromycin while causing significantly fewer gastrointestinal side effects. 1

First-Line Treatment Regimen

Azithromycin Dosing by Age

• Infants <1 month: 10 mg/kg per day for 5 days 1

  • Azithromycin is specifically preferred in this age group due to significantly lower risk of infantile hypertrophic pyloric stenosis (IHPS) compared to erythromycin 1

• Infants 1-5 months: 10 mg/kg per day for 5 days 1

• Infants ≥6 months and children: 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg per day (maximum 250 mg) on days 2-5 1

• Adults: 500 mg on day 1, followed by 250 mg per day on days 2-5 1

Key Administration Points

• Do not administer azithromycin simultaneously with aluminum- or magnesium-containing antacids as they reduce absorption 1
• Isolate the patient at home and away from work/school for 5 days after starting antibiotics to prevent transmission 1

Alternative Treatment Options

Clarithromycin

• Infants 1-5 months: 15 mg/kg per day divided into two doses for 7 days 2
• Children and adults: 7.5 mg/kg (or 500 mg) twice daily for 7 days 3
• Clarithromycin is equally effective as azithromycin and erythromycin for microbiological eradication 1

Trimethoprim-Sulfamethoxazole (TMP-SMZ)

• Reserved for patients >2 months of age with macrolide contraindications 1
• Serves as an effective alternative for patients who cannot tolerate macrolides 4

Erythromycin (Use with Caution)

• Avoid in infants <1 month due to association with IHPS 1
• If erythromycin must be used: 40-50 mg/kg/day in children (divided doses) or 1-2 g per day in adults for 14 days 1, 5
• Erythromycin resistance remains rare (<1%) 1

Timing of Treatment: Critical for Effectiveness

Early Treatment (Catarrhal Phase - First 2 Weeks)

• Start antibiotics immediately upon clinical suspicion without waiting for culture confirmation 1
• Early treatment rapidly clears B. pertussis from the nasopharynx, decreases coughing paroxysms, and reduces complications 1
• This is the only phase where antibiotics can modify disease severity 6

Late Treatment (Paroxysmal Phase - >3 Weeks)

• Antibiotics have limited clinical benefit on symptoms but remain indicated to prevent transmission 1
• Approximately 80-90% of untreated patients spontaneously clear B. pertussis within 3-4 weeks from cough onset 1

Comparative Efficacy Evidence

• A large multicenter randomized trial demonstrated 100% bacterial eradication with both azithromycin (5 days) and erythromycin (10 days), with no bacterial recurrence in either group 7
• Gastrointestinal adverse events occurred in only 18.8% of azithromycin recipients versus 41.2% of erythromycin recipients 7
• Compliance was markedly superior with azithromycin: 90% took 100% of prescribed doses versus only 55% with erythromycin 7

Therapies That Do NOT Work

• Do not use long-acting β-agonists, antihistamines, corticosteroids, or pertussis immunoglobulin—these have no proven benefit in controlling coughing paroxysms 1

Postexposure Prophylaxis for Close Contacts

Who Requires Prophylaxis

• All household contacts regardless of age or vaccination status 2, 3
• High-priority groups: Infants <12 months (especially <4 months) and women in third trimester of pregnancy 1, 3
• Healthcare workers with known exposure should receive prophylaxis or be monitored daily for 21 days 3

Prophylaxis Regimen

• Use the same antimicrobial agents and dosing regimens as treatment 1, 2
• Administer within 21 days of exposure for effectiveness 3
• Goal is to eradicate B. pertussis from the nasopharynx of infected persons (symptomatic or asymptomatic) and create a protective "cocoon" around vulnerable infants 2, 3

Important Caveats and Pitfalls

• Pertussis is highly infectious with secondary attack rates exceeding 80% among susceptible household contacts 3
• Patients are most infectious during the catarrhal stage and first 3 weeks after cough onset 3
• Antibiotic prophylaxis does not provide long-term protection; vaccination remains the most important preventive strategy 3
• Vaccine immunity wanes after 5-10 years, making previously vaccinated adolescents and adults susceptible 3
• Macrolides (erythromycin and clarithromycin, but NOT azithromycin) inhibit cytochrome P450 enzymes and can interact with other medications (digoxin, triazolam, ergot alkaloids) 1