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

Management of Pertussis

Patients with confirmed or suspected pertussis should receive azithromycin as first-line treatment and be isolated for 5 days from the start of antibiotic therapy to prevent transmission. 1

Antibiotic Treatment

First-Line Agent: Azithromycin

Azithromycin is the preferred macrolide for all age groups due to superior tolerability, convenient dosing, and lower risk of serious adverse effects compared to erythromycin. 1

Dosing regimens:

• Adults: 500 mg on day 1, followed by 250 mg daily on days 2-5 1
• Children ≥6 months: 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg daily (maximum 250 mg) on days 2-5 1
• Infants <6 months: 10 mg/kg daily for 5 days 1

Critical consideration for infants <1 month: Azithromycin is strongly preferred over erythromycin due to the significant association between erythromycin and infantile hypertrophic pyloric stenosis (IHPS). 1

Alternative Agents

• Clarithromycin: Equally effective as azithromycin and erythromycin; recommended for infants 1-5 months as an alternative first-line option 1
• Trimethoprim-sulfamethoxazole (TMP-SMZ): For patients >2 months with macrolide contraindications or allergies 1
• Erythromycin: 40-50 mg/kg/day in children and 1-2 g/day in adults for 14 days; avoid in infants <1 month due to IHPS risk 1, 2

Important drug interactions: Erythromycin and clarithromycin (but NOT azithromycin) inhibit cytochrome P450 enzymes and can interact with digoxin, triazolam, and ergot alkaloids. 1 Azithromycin should not be taken with aluminum- or magnesium-containing antacids as they reduce absorption. 1

Timing of Treatment: Critical for Effectiveness

Start antibiotics immediately upon clinical suspicion without waiting for culture confirmation. 1

Early Treatment (Catarrhal Phase, First 2 Weeks)

• Rapidly clears B. pertussis from the nasopharynx 3, 1
• Decreases coughing paroxysms and reduces complications 3, 1
• Most effective period for clinical benefit 3, 1

Late Treatment (Paroxysmal Phase, >3 Weeks After Cough Onset)

• Limited clinical benefit for the patient 1
• Still indicated to prevent transmission to others 1
• Approximately 80-90% of untreated patients spontaneously clear B. pertussis within 3-4 weeks 1

Isolation and Infection Control

Isolate patients at home and away from work/school for 5 days after starting antibiotics. 3, 1, 4

Without antibiotic treatment, isolate for 21 days after cough onset. 4

Pertussis is highly contagious with a secondary attack rate exceeding 80% among susceptible persons. 3, 5 Patients are most infectious during the catarrhal stage and first 3 weeks after cough onset. 3, 5

Diagnostic Confirmation

Obtain nasopharyngeal aspirate or Dacron swab for culture to confirm diagnosis. 3

• Culture: The only certain way to make the diagnosis; isolation of bacteria is definitive 3
• PCR testing: Available but not universally standardized for routine clinical use as of 2006 guidelines 3
• Serology: Fourfold increase in IgG or IgA antibodies to pertussis toxin (PT) or filamentous hemagglutinin (FHA) on paired acute and convalescent sera suggests recent infection 3

Clinical diagnosis criteria: Cough lasting ≥2 weeks with paroxysms, post-tussive vomiting, and/or inspiratory whoop should be presumed pertussis unless proven otherwise. 3

Therapies That Do NOT Work

Do not use the following as they provide no benefit in controlling coughing paroxysms: 3, 1

• Long-acting β-agonists
• Antihistamines
• Corticosteroids
• Pertussis immunoglobulin

This recommendation is based on good quality evidence showing no clinical benefit. 3

Post-Exposure Prophylaxis (PEP)

Administer the same antibiotic regimens used for treatment to close contacts within 21 days of exposure. 1, 5

Priority Groups for PEP:

• All household contacts (strongly recommended) 5
• Infants <12 months, especially <4 months (highest risk of severe disease and death) 3, 5
• Pregnant women in third trimester 5
• Healthcare workers with known exposure (either receive PEP or be monitored daily for 21 days) 5

Rationale: PEP aims to eradicate B. pertussis from the nasopharynx of infected persons (symptomatic or asymptomatic) and prevent transmission to vulnerable individuals. 5

Vaccination Considerations

Verify and update vaccination status for the patient and all household contacts. 1

• All children should receive DTaP primary vaccination series with booster in early adolescence 3
• Single dose Tdap recommended for adolescents 11-18 years and adults 19-64 years 3
• Pregnant women should receive Tdap between 27-36 weeks' gestation with each pregnancy to convey immunity to the newborn 6

Important caveat: Vaccine immunity wanes after 5-10 years, making previously vaccinated individuals susceptible to infection. 3, 5 Antibiotic prophylaxis does not provide long-term protection; vaccination remains the most important preventive strategy. 5

Common Pitfalls to Avoid

• Do not delay treatment waiting for culture results - start immediately on clinical suspicion 1
• Do not use erythromycin in infants <1 month due to IHPS risk; use azithromycin instead 1
• Do not assume vaccinated individuals are protected - immunity wanes significantly over time 3, 5
• Do not forget to treat close contacts - secondary attack rates exceed 80% 3, 5
• Remember the cough may persist for weeks to months despite appropriate treatment - this does not indicate treatment failure, as the patient is no longer contagious after 5 days of antibiotics 4