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

Pertussis Prophylaxis Recommendations

Azithromycin is the first-line antibiotic for pertussis post-exposure prophylaxis due to its once-daily dosing, excellent tolerability, and shorter treatment duration compared to other options. 1

Recommended Prophylactic Regimens

First-Line Treatment: Azithromycin

• Adults: 500 mg on day 1, then 250 mg daily for 4 days (5 days total)
• Children: 10 mg/kg on day 1, then 5 mg/kg daily for 4 days (5 days total) 1

Second-Line Treatment: Clarithromycin

• Adults: 500 mg twice daily for 7 days
• Children: 15 mg/kg/day in 2 divided doses for 7 days (maximum 1 g/day) 1

Third-Line Treatment: Erythromycin

• Adults: 500 mg four times daily for 14 days
• Children: 40-50 mg/kg/day in divided doses for 14 days 2, 3

Alternative (when macrolides cannot be used): Trimethoprim-Sulfamethoxazole

• Adults: Trimethoprim 320 mg/day, sulfamethoxazole 1,600 mg/day in 2 divided doses for 14 days
• Children (>2 months): Trimethoprim 8 mg/kg/day, sulfamethoxazole 40 mg/kg/day in 2 divided doses for 14 days 1

Key Considerations for Prophylaxis

Timing and Effectiveness

• Prophylaxis is most effective when initiated within 2 weeks of exposure 1
• Close contacts should receive the same antibiotic regimens as for treatment, regardless of vaccination status 1

Who Should Receive Prophylaxis

• Household contacts of pertussis cases 2, 1
• Individuals at high risk of severe pertussis (infants, pregnant women in third trimester, immunocompromised persons) 4
• Individuals who have close contact with high-risk persons 4

Isolation Recommendations

• Patients with pertussis should be isolated at home and away from work or school for 5 days after starting antibiotic therapy 1
• Healthcare workers with pertussis should be restricted from work during the first 5 days of antimicrobial therapy 1

Advantages of Newer Macrolides Over Erythromycin

1. Improved Tolerability:

   • Erythromycin causes significant gastrointestinal side effects (epigastric distress, abdominal cramps, nausea, vomiting, diarrhea) 1
   • Azithromycin and clarithromycin have lower incidence of GI side effects 1

2. Simplified Dosing:

   • Erythromycin requires four-times-daily dosing, reducing compliance 1, 3
   • Azithromycin (once daily) and clarithromycin (twice daily) offer improved dosing regimens 1

3. Safety Concerns:

   • Erythromycin is associated with infantile hypertrophic pyloric stenosis in infants under 1 month 1
   • Erythromycin inhibits cytochrome P450 enzymes, leading to potentially serious drug interactions 1

Important Caveats and Pitfalls

• Trimethoprim-sulfamethoxazole is contraindicated in infants under 2 months, pregnant women, and nursing mothers 1
• Antibiotics are intended to prevent transmission of pertussis and do not shorten the disease course or improve symptoms in the infected individual 4
• Vaccination remains the most effective prevention strategy against pertussis 2, 1, 5
• Neither vaccination nor natural disease confers lifelong immunity; immunity wanes after 5-10 years 2
• Cocooning (vaccinating close contacts of high-risk individuals) is no longer recommended as the primary strategy since immunized patients can still contract and transmit pertussis 4

Vaccination Recommendations

• Children: 5 doses of DTaP vaccine at ages 2,4,6,15-18 months, and 4-6 years 2, 1
• Adolescents and Adults: At least one dose of Tdap 4
• Pregnant Women: Tdap between 27-36 weeks' gestation with each pregnancy to provide immunity to the newborn 4