What is the recommended treatment for suspected whooping cough (pertussis) in an 18-month-old non-immunized male with exposure?

Treatment of Suspected Whooping Cough in Non-Immunized 18-Month-Old with Exposure

Start azithromycin immediately at 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg (maximum 250 mg) daily on days 2-5, without waiting for diagnostic confirmation. 1

Immediate Antibiotic Treatment

• Azithromycin is the first-line agent for this age group due to superior tolerability, convenient dosing, and equal efficacy to erythromycin 1
• Begin treatment immediately upon clinical suspicion—do not delay for culture confirmation, as early treatment rapidly clears B. pertussis from the nasopharynx and decreases coughing paroxysms 1
• Treatment is most effective during the catarrhal phase (first 2 weeks), but even late treatment remains critical to prevent transmission to other vulnerable individuals 1

Alternative if macrolide contraindication exists: Trimethoprim-sulfamethoxazole (TMP-SMZ) can be used in children >2 months with macrolide allergies 1

Critical Infection Control Measures

• Isolate the child at home for 5 days after starting antibiotics to prevent spread, as pertussis has a secondary attack rate exceeding 80% among susceptible household contacts 1
• If antibiotics cannot be administered, isolation must continue for 21 days after cough onset 2

Household Contact Management

• All household and close contacts require prophylaxis with the same antibiotic regimen (azithromycin at treatment doses) within 21 days of exposure, regardless of their vaccination status 1, 2
• This is especially critical if the household includes infants <12 months or pregnant women in their third trimester 1
• Verify and update vaccination status of all household contacts immediately 3

Diagnostic Confirmation

• Obtain nasopharyngeal aspirate or Dacron swab for culture and PCR testing to confirm B. pertussis, as culture isolation is the only definitive diagnostic method 1
• Do not wait for results before initiating treatment 1

Vaccination Catch-Up

• Begin the DTaP primary vaccination series immediately for this non-immunized child 1
• The child remains at extremely high risk for severe disease and complications given the lack of any vaccine-induced immunity 4

Therapies to Avoid

• Do not use β-agonists, antihistamines, corticosteroids, or pertussis immunoglobulin—these have no proven benefit in controlling coughing paroxysms 1

Monitoring for Complications

• Watch for weight loss, sleep disturbance, and post-tussive vomiting, which occur frequently 2
• Monitor for pressure-related effects from severe coughing including pneumothorax, epistaxis, and subconjunctival hemorrhage 2
• Be vigilant for secondary bacterial pneumonia, otitis media, seizures, and hypoxic encephalopathy, which require immediate evaluation 2

Important Caveats

• Non-immunized children face substantially higher risk of severe disease, prolonged symptoms, and complications compared to vaccinated children 2
• Azithromycin should not be taken with aluminum- or magnesium-containing antacids as they reduce absorption 1
• Even though antibiotics may not shorten the clinical course if started during the paroxysmal phase, they remain essential for eradicating the organism and preventing transmission 5, 6
• Approximately 80-90% of untreated patients spontaneously clear B. pertussis within 3-4 weeks, but the transmission risk during this period is unacceptably high 1