What antihistamine (anti-allergic medication) can be used to treat a dry cough?

Antihistamines for Dry Cough

First-generation antihistamines (such as dexbrompheniramine or azatadine) combined with a decongestant are the only antihistamine formulations recommended for dry cough, while second-generation antihistamines (like loratadine, cetirizine, or fexofenadine) are ineffective and should not be used for this indication. 1

Key Distinction: First-Generation vs Second-Generation Antihistamines

The critical difference lies in the mechanism of action:

• First-generation antihistamines work through their anticholinergic properties, not their antihistamine effects, which is why they suppress cough 1
• Second-generation antihistamines lack significant anticholinergic activity and have been proven ineffective in multiple studies for cough suppression 1

Recommended First-Generation Antihistamine Regimens

For upper airway cough syndrome (post-nasal drip) or post-viral cough:

• Dexbrompheniramine 6 mg twice daily PLUS pseudoephedrine 120 mg sustained-release twice daily 1
• OR Azatadine 1 mg twice daily PLUS pseudoephedrine 120 mg sustained-release twice daily 1

These combinations have Grade A evidence (substantial benefit) for cough suppression 1

Clinical Algorithm for Antihistamine Use in Dry Cough

Step 1: Determine if antihistamines are appropriate

• Antihistamines are indicated for cough related to upper airway disease (post-nasal drip syndrome) 1
• They are particularly useful for nocturnal cough due to their sedative effects 2, 3

Step 2: Select the correct generation

• Use ONLY first-generation antihistamines combined with decongestants 1
• Avoid second-generation antihistamines (loratadine, cetirizine, fexofenadine) as they are ineffective 1

Step 3: Manage sedation side effects

• Start with once-daily dosing at bedtime for several days before advancing to twice-daily dosing 1
• This approach can minimize daytime sedation while capitalizing on the benefit for nighttime cough 1

Step 4: Monitor response

• Most patients show improvement within days to 2 weeks 1
• If no response after 2 weeks, reconsider the diagnosis 1

Important Contraindications and Cautions

Decongestant component contraindications:

• Glaucoma (increased intraocular pressure) 1
• Benign prostatic hypertrophy (urinary retention) 1
• Uncontrolled hypertension 1
• Tachycardia or palpitations 1

Antihistamine component side effects:

• Sedation (most common) 1
• Dry mouth 1
• Urinary retention in older men 1

Critical Pitfalls to Avoid

1. Do NOT prescribe second-generation antihistamines for cough - Studies with terfenadine and loratadine showed no efficacy for acute cough 1

2. Do NOT use antihistamines alone without decongestants - The combination is what provides efficacy for upper airway cough 1

3. Do NOT use antihistamines for common cold cough - Over-the-counter combination cold medications (except older antihistamine-decongestant combinations) are not recommended until proven effective in randomized trials 1

4. Do NOT continue beyond 2-4 weeks without reassessment - Lack of response suggests an alternative diagnosis 1

When Antihistamines Are NOT Indicated

• Acute cough from common cold - Limited efficacy, not recommended (Grade D) 1
• Chronic bronchitis - Use peripheral or central cough suppressants instead 1
• Productive cough - Antihistamines may impair secretion clearance 2
• Cough not related to upper airway disease - Consider alternative diagnoses 1

Alternative First-Line Options for Dry Cough

If antihistamines are contraindicated or ineffective:

• Dextromethorphan 60 mg for bronchitis or severe symptoms 2, 3
• Ipratropium bromide inhaled for URI-related cough (Grade A recommendation) 1, 2
• Simple remedies like honey and lemon may be as effective as pharmacological treatments 2, 3