What is the recommended treatment for prophylaxis in individuals exposed to pertussis (whooping cough) and exhibiting symptoms?

Treatment of Symptomatic Pertussis Exposure

Individuals who have been exposed to pertussis and are showing symptoms should receive immediate antimicrobial treatment with azithromycin as the preferred first-line agent, not prophylaxis, as they are considered to have active infection. 1

Recommended Treatment Regimen

First-line Treatment (Preferred):

• Azithromycin:
  • Infants <6 months: 10 mg/kg per day for 5 days
  • Infants and 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
  • Adults: 500 mg on day 1, followed by 250 mg per day on days 2-5 1

Alternative Treatments:

• Clarithromycin:

  • Adults: 500 mg twice daily for 7 days
  • Children: 15-20 mg/kg/day in two divided doses for 7 days 2, 1

• Erythromycin (not preferred due to side effects):

  • Adults: 500 mg four times daily or delayed-release tablets 333 mg three times daily for 14 days
  • Children: 40-50 mg/kg/day divided into four doses for 14 days
  • Not recommended for infants <1 month due to risk of infantile hypertrophic pyloric stenosis 2, 1

• Trimethoprim-sulfamethoxazole (for macrolide-intolerant patients):

  • Adults: One double-strength tablet twice daily for 14 days
  • Children: 8 mg/kg/day TMP, 40 mg/kg/day SMX in 2 divided doses for 14 days
  • Not recommended for pregnant women at term, nursing mothers, or infants <2 months 2

Important Clinical Considerations

Disease Progression

Pertussis progresses through three stages 2, 3:

1. Catarrhal stage (1-2 weeks): Nasal congestion, runny nose, mild sore throat, dry cough, minimal or no fever
2. Paroxysmal stage: Characterized by severe coughing fits often ending with inspiratory "whoop" and post-tussive vomiting
3. Convalescent stage: Gradual recovery with decreasing frequency of cough paroxysms

Isolation Precautions

• Patients 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 2

Monitoring and Follow-up

• Monitor for 21 days after exposure for development of symptoms 1
• Be aware that antibiotics eliminate the bacteria but may not alter the clinical course once symptoms are established 4
• Supportive care is essential for managing cough paroxysms and preventing complications 5

Special Populations

Infants and Young Children

• Infants are at highest risk for severe disease and death 2, 5
• Azithromycin is strongly preferred for infants <1 month due to risk of infantile hypertrophic pyloric stenosis with erythromycin 1
• Monitor closely for apnea, particularly in infants <6 months 5

Pregnant Women

• Pregnant women should receive prompt treatment if symptomatic 1
• Azithromycin is generally considered safe during pregnancy 1, 3

Common Pitfalls to Avoid

1. Misclassifying as prophylaxis: Symptomatic individuals require treatment, not prophylaxis, as they likely have active infection 1, 3

2. Delayed treatment: Early treatment is crucial to reduce transmission, though it may not significantly alter the clinical course once coughing paroxysms have begun 4

3. Poor medication adherence: Consider side effect profiles when selecting antibiotics - macrolides other than erythromycin have fewer side effects and better compliance 6

4. Inappropriate antibiotic use during late disease: Antibiotics should not be used prophylactically at late periods of pertussis to prevent secondary bacterial complications 7

5. Failure to identify and treat contacts: Close contacts of symptomatic individuals should receive prophylaxis regardless of vaccination status 2, 3