Treatment of Suspected Pertussis (Whooping Cough)
Start a macrolide antibiotic immediately upon clinical suspicion without waiting for diagnostic confirmation, as early treatment rapidly clears Bordetella pertussis from the nasopharynx, diminishes coughing paroxysms, prevents complications, and stops disease transmission. 1
Immediate Management Algorithm
Step 1: Initiate Treatment Without Delay
- Begin antibiotics as soon as pertussis is suspected based on clinical presentation (cough ≥2 weeks with paroxysms, post-tussive vomiting, or inspiratory whoop) 2, 1
- Do not wait for laboratory confirmation, as treatment effectiveness depends critically on early initiation during the catarrhal phase (first 2 weeks of illness) 1, 3
- Isolate the patient immediately for 5 days from the start of antibiotic treatment to prevent transmission 2, 1
Step 2: First-Line Antibiotic Selection
Azithromycin is the preferred agent for all age groups due to superior tolerability, better compliance, equal efficacy to erythromycin, and significantly lower risk of infantile hypertrophic pyloric stenosis (IHPS). 1
Dosing regimens: 1
- Infants <6 months: 10 mg/kg/day for 5 days
- Infants ≥6 months and children: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg/day (max 250 mg) on days 2-5
- Adults: 500 mg on day 1, then 250 mg/day on days 2-5
Critical caveat: Do not administer azithromycin with aluminum- or magnesium-containing antacids as they reduce absorption 1
Step 3: Alternative Antibiotics
If azithromycin is unavailable or contraindicated: 1
Erythromycin (second-line):
Trimethoprim-Sulfamethoxazole (for macrolide contraindications):
- Only for patients >2 months of age 1
Diagnostic Testing (Concurrent with Treatment)
While treatment should never be delayed, obtain diagnostic confirmation: 2, 1
- Collect nasopharyngeal aspirate or Dacron swab for culture (100% specific but takes 1-2 weeks) 2, 4
- PCR testing is preferred if available (80-100% sensitivity, faster turnaround) 4, 5
Treatment Timing and Expected Outcomes
Early treatment (catarrhal phase, first 2 weeks): 1
- Provides maximum clinical benefit
- Rapidly clears bacteria from nasopharynx
- Reduces coughing paroxysms and complications
- Prevents transmission
Late treatment (paroxysmal phase, >3 weeks): 2, 1
- Limited clinical benefit for symptom reduction
- Still indicated to prevent transmission to others
- Patient unlikely to respond symptomatically but remains contagious without treatment
Important reality: Cough may persist for weeks to months despite appropriate antibiotic treatment, but the patient is no longer contagious after 5 days of antibiotics 1
Isolation and Return to Activities
- With antibiotics: Patient may return to school/work after 5 days of treatment 1
- Without antibiotics: Patient must remain isolated for 21 days after cough onset 1
Treatments That Do NOT Work
Do not prescribe the following, as they provide no benefit: 2
- Long-acting β-agonists
- Antihistamines
- Corticosteroids
- Pertussis immunoglobulin
This recommendation is based on good quality evidence showing no benefit 2
Postexposure Prophylaxis for Contacts
Use the same antibiotic regimens and dosing as for treatment in: 1
- All household contacts
- High-priority groups: infants <12 months, pregnant women in third trimester, healthcare workers with known exposure
- Must be administered within 21 days of exposure
Key Clinical Pitfalls to Avoid
- Do not delay treatment waiting for test results - the window for clinical benefit closes rapidly 1, 3
- Do not dismiss pertussis in vaccinated individuals - vaccine immunity wanes after 5-10 years, and illness may be milder without the classic whoop 3, 5
- Do not use erythromycin in infants <6 months - significant IHPS risk 1
- Do not expect antibiotics to stop the cough immediately - they prevent transmission but may not alter the clinical course if started late 6
- Do not forget to isolate the patient - pertussis is highly contagious, especially during the catarrhal stage when symptoms are nonspecific 3, 7