What is the treatment algorithm for a patient diagnosed with whooping cough (pertussis)?

Treatment Algorithm for Whooping Cough (Pertussis)

All patients with confirmed or probable whooping cough should receive a macrolide antibiotic immediately upon clinical suspicion and be isolated for 5 days from the start of treatment, as early therapy within the first few weeks diminishes coughing paroxysms and prevents disease spread. 1

Immediate Actions Upon Suspicion

• Start antibiotics immediately without waiting for diagnostic 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, 2
• Obtain nasopharyngeal aspirate or Dacron swab for culture to confirm diagnosis, though treatment should not be delayed 1
• Isolate the patient at home and away from work/school for 5 days after starting antibiotics to prevent transmission 1, 2

First-Line Antibiotic Treatment

Azithromycin (Preferred Agent)

Azithromycin is the first-line agent for all age groups due to superior tolerability, better compliance, and equal efficacy compared to erythromycin. 2, 3

Dosing by Age:

• Infants <6 months: 10 mg/kg/day for 5 days 2
• Infants ≥6 months and children: 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg/day (maximum 250 mg) on days 2-5 2
• Adults: 500 mg on day 1, then 250 mg/day on days 2-5 2

Key Advantages:

• Significantly lower risk of infantile hypertrophic pyloric stenosis (IHPS) compared to erythromycin in infants <1 month 2
• Gastrointestinal adverse events occur in only 18.8% of patients versus 41.2% with erythromycin 3
• 90% compliance rate versus 55% with erythromycin 3
• Do not administer with aluminum- or magnesium-containing antacids as they reduce absorption 2

Alternative: Clarithromycin

• Recommended as first-line for infants 1-5 months of age alongside azithromycin 2
• Equally effective as erythromycin with better side-effect profile 1

Second-Line Treatment

Erythromycin

Use only when macrolides like azithromycin are unavailable; avoid in infants <6 months due to IHPS risk. 2, 4

Dosing:

• Children: 40-50 mg/kg/day in divided doses for 14 days 1, 4
• Adults: 1-2 g/day in divided doses for 14 days 1, 4
• Pertussis-specific dosing: 40-50 mg/kg/day in divided doses for 5-14 days 4

Critical Warnings:

• Associated with IHPS in infants <1 month; avoid if possible 2
• Inhibits cytochrome P450 enzyme system; check for drug interactions 2
• Resistance is rare (<1%) 1

Alternative for Macrolide Contraindications

Trimethoprim-Sulfamethoxazole (TMP-SMZ)

• For patients >2 months with macrolide contraindications or hypersensitivity 2
• Effective in eradicating B. pertussis 5

Treatment Timing and Expected Outcomes

Early Treatment (Catarrhal Phase: First 2 Weeks)

• Maximum clinical benefit: Rapidly clears bacteria, reduces coughing paroxysms, and prevents complications 1, 2
• This is the critical window for effective treatment 1

Late Treatment (Paroxysmal Phase: >3 Weeks)

• Limited clinical benefit for symptom reduction 2
• Still indicated to prevent transmission to others 2
• Approximately 80-90% of untreated patients spontaneously clear B. pertussis within 3-4 weeks 2

Important Caveat:

• Cough may persist for weeks to months despite appropriate antibiotic treatment, but the patient is no longer contagious after 5 days of antibiotics 6
• Antibiotics eliminate bacteria but do not alter the subsequent clinical course once paroxysmal stage is established 5

Therapies That Do NOT Work

Do not prescribe the following as they have no proven benefit: 1, 2

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

Postexposure Prophylaxis

Use the same antibiotic regimens and dosing as for treatment. 2

Indications for Prophylaxis:

• All household contacts 2
• High-priority groups: Infants <12 months, pregnant women in third trimester, healthcare workers with known exposure 2, 6
• Administer within 21 days of exposure 2

Return to School/Work Timeline

• With antibiotics: May return after 5 days of treatment 1, 2, 6
• Without antibiotics: Must remain isolated for 21 days after cough onset 6

Vaccination Considerations

• Verify and update patient's vaccination status 2
• Pregnant women should receive Tdap between 27-36 weeks' gestation with each pregnancy to convey immunity to newborn 2, 7
• Vaccine immunity wanes after 5-10 years, making previously vaccinated individuals susceptible 2
• Ensure all household contacts are up to date with pertussis vaccination 2