What is the best course of treatment for a 17-year-old female with a persistent dry cough, sometimes occurring throughout the day, and lasting for one month?

Management of Persistent Dry Cough in a 17-Year-Old Female

Start with a first-generation antihistamine-decongestant combination (such as brompheniramine 2-4 mg plus pseudoephedrine 30-60 mg twice daily) as empiric first-line therapy, as this one-month duration qualifies as subacute cough and upper airway cough syndrome (UACS) is the most likely diagnosis. 1, 2

Initial Assessment and Diagnosis

• At one month duration, this cough is classified as subacute cough (3-8 weeks), which most commonly represents either postinfectious cough or early upper airway cough syndrome 3, 1

• The dry nature of the cough suggests UACS or postinfectious cough rather than productive chronic bronchitis 3, 1

• Critical first step: Confirm the patient is not taking an ACE inhibitor, as these cause cough in a significant percentage of patients and resolution typically occurs within 26 days of discontinuation 3, 1

• Perform focused physical examination looking for:

  • Cobblestoning of posterior pharyngeal wall (hallmark of UACS) 2
  • Nasal discharge or throat clearing 1, 2
  • Clear lung fields to exclude pneumonia 4

• Obtain chest radiograph to rule out structural abnormalities, masses, or interstitial disease 1

First-Line Treatment Algorithm

Initiate empiric therapy with a first-generation antihistamine-decongestant combination immediately, as this has the strongest evidence for both UACS and postinfectious cough 2, 5:

• Specific effective combinations include:

  • Brompheniramine 2-4 mg plus pseudoephedrine 30-60 mg twice daily 2, 6
  • Dexbrompheniramine plus sustained-release pseudoephedrine 2
  • Chlorpheniramine plus sustained-release pseudoephedrine 2

• To minimize sedation: Start with once-daily dosing at bedtime for a few days, then increase to twice-daily therapy 2

• Expected response time: Most patients improve within days to 2 weeks 2, 4

• Important caveat: Newer-generation antihistamines (cetirizine, loratadine, fexofenadine) are ineffective for non-allergic UACS and should not be used 2, 5

If No Response After 1-2 Weeks

Add intranasal corticosteroid spray (fluticasone 100-200 mcg daily) for a 1-month trial 1, 2:

• This is particularly effective if allergic rhinitis is suspected 2
• Continue the antihistamine-decongestant combination while adding the nasal steroid 2

Consider inhaled ipratropium bromide 2-3 puffs four times daily if postinfectious cough is more likely 4:

• This has the strongest evidence for attenuating postinfectious cough 4
• Response typically occurs within 1-2 weeks 4

If Cough Persists Beyond 8 Weeks (Chronic Cough)

Systematically evaluate and treat the three most common causes sequentially, which together account for 90% of chronic cough cases 1, 7, 8:

1. Upper Airway Cough Syndrome (UACS)

• Continue or optimize antihistamine-decongestant plus intranasal corticosteroid 1, 2
• Add ipratropium bromide nasal spray if rhinorrhea is prominent 2

2. Asthma

• Perform spirometry with bronchodilator response or bronchoprovocation challenge 1
• If testing unavailable, initiate empiric trial of inhaled corticosteroids (fluticasone 220 mcg twice daily) plus bronchodilators 1
• Response may take up to 8 weeks 1, 4

3. Gastroesophageal Reflux Disease (GERD)

• Initiate high-dose proton pump inhibitor (omeprazole 40 mg twice daily before meals) for at least 8 weeks 1, 4
• Add dietary modifications and lifestyle changes 1
• Response may take 2 weeks to several months 1, 4

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for subacute dry cough unless there is clear evidence of bacterial sinusitis or pertussis 4

• Do not discontinue partially effective treatments when adding new therapies, as chronic cough is frequently multifactorial 1, 4

• Do not use newer-generation antihistamines (cetirizine, loratadine) as they lack the anticholinergic properties necessary for UACS treatment 2, 5

• Monitor blood pressure after initiating decongestants, as they can worsen hypertension 2

• Avoid topical nasal decongestants (oxymetazoline) for more than 3-5 days due to risk of rebound congestion 2

Red Flags Requiring Immediate Re-evaluation

• Development of fever, hemoptysis, weight loss, or night sweats 4
• Crackles on lung examination suggesting pneumonia 4
• Abnormal chest radiograph 1