What is the best over-the-counter (OTC) medication for postnasal drip and cough possibly caused by allergies?

Best OTC Medication for Post Nasal Drip and Cough Due to Allergies

For post nasal drip and cough possibly caused by allergies, a first-generation antihistamine/decongestant combination is the most effective over-the-counter treatment option. 1

Treatment Algorithm

First-line Treatment Options:

1. First-generation antihistamine/decongestant combination

   • Examples: Dexbrompheniramine plus pseudoephedrine 2
   • Mechanism: Antihistamines reduce secretions and inflammation while decongestants reduce nasal congestion 1
   • Dosing: Start with once daily dosing at bedtime for a few days before increasing to twice daily to minimize sedation 2

2. Intranasal corticosteroids

   • Particularly effective if allergic rhinitis is suspected 1
   • May take 1-2 weeks for full effect
   • Can be used alone or in combination with antihistamines

3. Saline nasal irrigation

   • Helps clear mucus and allergens
   • Improves ciliary activity and disrupts inflammatory mediators 1

Second-line Options:

• Second-generation (non-sedating) antihistamines (e.g., loratadine, cetirizine)
  • Less effective for non-allergic causes of post nasal drip 2, 3
  • More effective if allergic component is predominant 2

Evidence-Based Considerations

For Allergic Causes:

• If allergies are clearly the cause, second-generation antihistamines like loratadine may be sufficient 4, 3
• Adding intranasal corticosteroids provides better symptom control for moderate-severe symptoms 1, 3

For Non-Allergic or Mixed Causes:

• First-generation antihistamines work better than newer non-sedating antihistamines for non-allergic post nasal drip due to their anticholinergic properties 2
• Studies show that older-generation antihistamine/decongestant combinations are consistently effective for cough associated with post nasal drip 2

Important Caveats and Pitfalls

1. Side effects of first-generation antihistamines:

   • Sedation (can be minimized by starting with nighttime dosing) 2
   • Dry mouth
   • Urinary retention (caution in elderly and those with prostatic hypertrophy) 1

2. Decongestant precautions:

   • Should not be used longer than 5-7 days to prevent rebound congestion (rhinitis medicamentosa) 1
   • Use with caution in patients with hypertension, heart disease, glaucoma, or hyperthyroidism 1, 5

3. Treatment duration:

   • Expect improvement within days to 2 weeks of initiating therapy 2
   • If symptoms persist beyond 4 weeks despite appropriate treatment, further evaluation is warranted 1

4. Monitoring effectiveness:

   • Treatment response is both diagnostic and therapeutic 1
   • If no improvement after 2 weeks, consider alternative diagnoses or adding additional therapies

The evidence strongly supports first-generation antihistamine/decongestant combinations as the most effective OTC option for post nasal drip and cough, particularly when the cause is not clearly allergic in nature 2, 1. For predominantly allergic symptoms, second-generation antihistamines and intranasal corticosteroids may be more appropriate 1, 3.