In a healthy 42‑year‑old woman with a two‑week history of nocturnal dry cough and nasal congestion, what is the most likely diagnosis and appropriate first‑line treatment?

Upper Airway Cough Syndrome (Postnasal Drip)

This is Upper Airway Cough Syndrome (UACS), and you should start a first-generation antihistamine/decongestant combination immediately as first-line therapy. 1, 2

Understanding the Diagnosis

Your patient's two-week history of nocturnal dry cough with nasal congestion is the classic presentation of UACS, which accounts for 18.6%–81.8% of chronic cough cases and is the single most common cause of chronic cough in adults. 2 The nocturnal worsening occurs because gravity-driven drainage of nasal and sinus secretions into the hypopharynx directly irritates cough receptors when lying down. 2

UACS is a clinical diagnosis confirmed by response to treatment, not by physical examination alone. 1, 2 The symptoms and signs are nonspecific—approximately 20% of patients have "silent" postnasal drip with no obvious nasal symptoms yet still respond to treatment. 1, 2 This means you cannot rule out UACS based on the absence of visible posterior pharyngeal drainage or cobblestoning. 1, 2

The differential diagnosis includes allergic rhinitis (28% of UACS cases), chronic rhinitis (22%), chronic sinusitis (31%), and postinfectious rhinitis. 1, 3 However, at two weeks post-onset, this is still in the acute-to-subacute window where empiric treatment is more appropriate than extensive diagnostic workup. 1, 2

First-Line Treatment Algorithm

Start immediately with a first-generation antihistamine/decongestant combination such as:

• Dexbrompheniramine maleate plus sustained-release pseudoephedrine sulfate, OR
• Azatadine maleate plus sustained-release pseudoephedrine sulfate, OR
• Chlorpheniramine with sustained-release pseudoephedrine 2

Dosing strategy to minimize sedation: Start with once-daily dosing at bedtime for a few days, then increase to twice-daily therapy. 2 Most patients see improvement within days to 2 weeks. 2

Why first-generation antihistamines? They are superior to newer non-sedating antihistamines due to their anticholinergic properties that reduce secretions. 2 Newer-generation antihistamines (cetirizine, fexofenadine, loratadine) are ineffective for non-allergic UACS and should not be used for acute cough. 1, 2

Add Intranasal Corticosteroids

If no improvement after 1–2 weeks with the antihistamine-decongestant combination, add intranasal corticosteroids such as fluticasone 100–200 mcg daily for a 1-month trial. 2 Intranasal corticosteroids are effective for both allergic and non-allergic rhinitis-related UACS. 2, 4

For confirmed allergic rhinitis (if the patient has seasonal symptoms, itching of eyes/nose/throat, or known allergies), you can start intranasal corticosteroids immediately alongside the antihistamine-decongestant combination. 2, 4

Adjunctive Therapy

High-volume nasal saline irrigation (150 mL) improves outcomes through mechanical removal of mucus, enhanced ciliary activity, and disruption of inflammatory mediators. 2 It is more effective than saline spray because irrigation better expels secretions. 2

Alternative for Contraindications

If the patient has contraindications to decongestants (uncontrolled hypertension, cardiovascular disease, glaucoma, urinary retention), use ipratropium bromide nasal spray (42 mcg per spray, 2 sprays per nostril 4 times daily) as an alternative. 2 This provides anticholinergic drying effects without systemic cardiovascular side effects. 2

When to Escalate

If symptoms persist despite adequate upper airway treatment for 2 weeks, proceed with sequential evaluation for:

1. Asthma/cough-variant asthma – Consider bronchoprovocation testing or empiric trial of inhaled corticosteroids 1, 2
2. Gastroesophageal reflux disease (GERD) – Initiate omeprazole 20–40 mg twice daily before meals for at least 8 weeks plus dietary modifications 1, 2
3. Chronic sinusitis – Obtain sinus imaging (CT scan) if purulent nasal discharge persists or facial pain/pressure develops 1, 2

UACS, asthma, and GERD together account for approximately 90% of chronic cough cases, and chronic cough is frequently multifactorial. 2, 5 Maintain all partially effective treatments rather than discontinuing them prematurely. 2

Critical Monitoring and Side Effects

Monitor for common side effects:

• Dry mouth and transient dizziness (expected with first-generation antihistamines) 2
• Insomnia, urinary retention, jitteriness, tachycardia from decongestants 2
• Worsening hypertension—monitor blood pressure after initiating therapy 2
• Increased intraocular pressure in glaucoma patients 2

Never use topical nasal decongestants (oxymetazoline, xylometazoline) for more than 3–5 consecutive days due to the risk of rhinitis medicamentosa (rebound congestion). 2

Common Pitfalls to Avoid

• Do not fail to consider "silent" UACS as a causative factor before looking for less common causes of chronic cough. 1, 2
• Do not rely solely on physical examination—the absence of visible postnasal drainage or cobblestoning does not rule out UACS. 1, 2
• Do not confuse GERD with UACS—both can cause pharyngeal inflammation and throat symptoms; GERD may mimic or coexist with postnasal drip. 1, 2
• Do not prescribe antibiotics unless there is clear evidence of bacterial sinusitis (purulent discharge >10 days, facial pain, fever, air-fluid levels on imaging). 1, 6

Timeline Expectations

• Improvement expected: Days to 1–2 weeks with antihistamine-decongestant therapy 2
• Complete resolution: May take several weeks to a few months 2
• Reclassify as chronic cough: If symptoms persist beyond 8 weeks, systematic re-evaluation for UACS, asthma, and GERD is required 1, 2, 6