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

Whooping Cough Treatment

Azithromycin is the first-line treatment for pertussis across all age groups, with a 5-day course (10 mg/kg on day 1, then 5 mg/kg daily on days 2-5 for children; 500 mg on day 1, then 250 mg daily on days 2-5 for adults) being as effective as 14 days of erythromycin while causing significantly fewer gastrointestinal side effects and improving compliance. 1, 2

First-Line Antibiotic Therapy

Azithromycin Dosing by Age

• Infants <1 month: 10 mg/kg per day for 5 days (preferred over erythromycin due to lower risk of infantile hypertrophic pyloric stenosis) 1
• Infants 1-5 months: 10 mg/kg per day for 5 days 1
• Children ≥6 months: 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

Alternative Macrolides

• Clarithromycin is equally effective as azithromycin and can be used as first-line therapy, particularly in infants 1-5 months of age 1
• Dosing: 15 mg/kg per day divided into two doses for 7 days in children; 500 mg twice daily for 7 days in adults 3

Second-Line Option

• Trimethoprim-sulfamethoxazole (TMP-SMZ) for patients >2 months with macrolide contraindications (hypersensitivity to any macrolide agent) 1, 4

Timing of Treatment: Critical for Effectiveness

Start antibiotics immediately upon clinical suspicion—do not wait for culture confirmation. 5

• Early treatment (catarrhal phase, first 2 weeks): Rapidly clears B. pertussis from the nasopharynx, decreases coughing paroxysms, and reduces complications 5
• Late treatment (paroxysmal phase, >3 weeks): Limited clinical benefit but still indicated to prevent transmission 5
• Approximately 80-90% of untreated patients spontaneously clear bacteria within 3-4 weeks from cough onset 1

Isolation Requirements

• Isolate patients at home and away from work/school for 5 days after starting antibiotics 5
• Without treatment, patients remain infectious for approximately 3 weeks after cough onset 3

Post-Exposure Prophylaxis

Use the same antibiotic regimens and dosing as for treatment. 1, 3

Who Should Receive Prophylaxis

• All household contacts regardless of age or vaccination status 3
• High-priority contacts: Infants <12 months (especially <4 months), pregnant women in third trimester 1, 3
• Administer within 21 days of exposure for effectiveness 3

Rationale

• Pertussis has a secondary attack rate exceeding 80% among susceptible household contacts 3
• Prophylaxis aims to eradicate B. pertussis from the nasopharynx of infected persons (symptomatic or asymptomatic) and create a protective "cocoon" around vulnerable infants 6, 3

Evidence Supporting Azithromycin Superiority

• A large multicenter randomized trial demonstrated 100% bacterial eradication with both azithromycin (5 days) and erythromycin (14 days), but azithromycin caused significantly fewer gastrointestinal adverse events (18.8% vs 41.2%) 2
• Compliance was markedly superior with azithromycin: 90% of children took 100% of prescribed doses versus only 55% with erythromycin 2
• Cochrane systematic review confirmed short-term antibiotics (azithromycin 3 days, clarithromycin 7 days) were equally effective as 14-day erythromycin with fewer side effects (RR 0.66; 95% CI 0.52-0.83) 7

Important Medication Considerations

Azithromycin Precautions

• Do not administer simultaneously with aluminum- or magnesium-containing antacids (reduces absorption) 1
• Use with caution in patients with impaired hepatic function 1
• Monitor for drug interactions with agents metabolized by cytochrome P450 (digoxin, triazolam, ergot alkaloids) 1

Erythromycin Warnings

• Associated with infantile hypertrophic pyloric stenosis (IHPS) in infants <1 month—avoid if possible 1, 6
• If erythromycin must be used: 40-50 mg/kg/day in children, 1-2 g per day in adults for 14 days 5, 4
• Erythromycin resistance is rare (<1%) 5

Therapies That Do NOT Work

• Long-acting β-agonists, antihistamines, corticosteroids, and pertussis immunoglobulin have no significant benefit in controlling coughing paroxysms 5

Common Pitfalls to Avoid

• Delaying treatment while awaiting culture results: Start antibiotics immediately based on clinical suspicion (cough >2 weeks with paroxysms, post-tussive vomiting, or inspiratory whoop) 5
• Failing to provide prophylaxis to household contacts: This is critical to prevent severe disease in vulnerable infants 3
• Using erythromycin in young infants: Azithromycin is safer due to lower IHPS risk 1, 6
• Expecting antibiotics to stop established paroxysms: Antibiotics eliminate bacteria and prevent transmission but do not alter the clinical course once paroxysmal coughing is established 7, 2