Anti allergic drugs used in ENT

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Anti-Allergic Drugs Used in ENT

Allergic conditions in ENT practice - primarily allergic rhinitis, allergic otitis, urticaria, and angioedema - are managed with a stepwise pharmacological approach. Below is a systematic classification.

1. Antihistamines (H1 Receptor Antagonists)

The backbone of anti-allergic therapy. They block H1 receptors, reducing itching, sneezing, and rhinorrhea. Classified into two generations:

First-Generation (Sedating)

Drug	Notes
Diphenhydramine	Highly sedating; significant anticholinergic effects
Chlorpheniramine	Most commonly used; moderate sedation
Promethazine	Strong antiemetic + antihistamine; useful in vertigo/vestibular allergy
Hydroxyzine	Useful in urticaria and pruritus
Cyclizine / Meclizine	Used in vestibular disorders and motion sickness in ENT

Cross the blood-brain barrier readily
Significant anticholinergic side effects (dry mouth, urinary retention, constipation)
Tachyphylaxis can develop
Avoid in patients performing skilled tasks (pilots, drivers)

Second-Generation (Non-Sedating)

Drug	Notes
Loratadine	Lipophobic; minimal CNS effects; OTC
Fexofenadine	Least sedating; no QTc prolongation; safe in cardiac patients
Cetirizine	Slightly sedating at higher doses; fast onset
Desloratadine	Active metabolite of loratadine; potent
Levocetirizine	R-enantiomer of cetirizine; highly potent

Lipophobic - do not cross the BBB readily
Little to no anticholinergic activity
Safe in asthma patients
Metabolized by CYP3A4 - be aware of CYP3A4 inhibitors (e.g., erythromycin, ketoconazole)
Little tachyphylaxis; strongly recommended for allergic rhinitis

Topical (Intranasal) Antihistamines

Drug	Notes
Azelastine	Most commonly used; rapid onset; as effective or superior to oral antihistamines for nasal congestion
Olopatadine	Available for nasal and ocular use

Work directly at target organ (nose, eyes)
At least as effective as intranasal corticosteroids for sneezing, itching, rhinorrhea, and ocular symptoms
Best used in combination with intranasal corticosteroids (not as monotherapy)

Key Point (Cummings Otolaryngology): "The most effective combination for the treatment of allergic rhinitis is an intranasal steroid with an intranasal antihistamine."

2. Intranasal Corticosteroids (First-Line Therapy)

The most effective class for allergic rhinitis - superior to antihistamines and leukotriene receptor antagonists for controlling nasal inflammation.

Drug	Notes
Fluticasone propionate	Low systemic bioavailability; onset within 12 hours; aqueous spray
Fluticasone furoate	More potent; once daily; very low bioavailability
Mometasone furoate	Very low systemic absorption; approved from age 2
Budesonide	Only intranasal steroid with Pregnancy Category B; aqueous, scent-free
Triamcinolone acetonide	Available OTC in the US; aqueous spray
Beclomethasone dipropionate	Older agent; higher systemic bioavailability; may cause growth suppression in children
Ciclesonide	Prodrug activated locally; minimal systemic effects
Flunisolide	Significant systemic bioavailability; poorly tolerated due to propylene glycol base

Key points:

First-line therapy for allergic rhinitis (except mildest cases)
Start 2 weeks before pollen season
Daily dosing more efficacious than as-needed dosing
Side effects: epistaxis, nasal dryness, local irritation; rare septal perforation
Aim spray away from the nasal septum
Newer agents generally free of HPA axis suppression
May have a negative effect on short-term growth in children - use the lowest effective dose

3. Leukotriene Receptor Antagonists (LTRAs)

Block leukotriene receptors on target cells, reducing nasal congestion, rhinorrhea, and sneezing.

Drug	Notes
Montelukast	Only agent approved for allergic rhinitis; also for asthma and exercise-induced bronchospasm; approved from 6 months of age
Zafirlukast	Used in asthma; less evidence in rhinitis

Efficacy parallels antihistamines but inferior to intranasal corticosteroids
Particularly useful in patients with concurrent asthma (unified airway disease)
Not recommended as monotherapy or first-line for allergic rhinitis
Can be second-line or when intranasal corticosteroids are contraindicated

4. Mast Cell Stabilizers

Drug	Mechanism	Notes
Cromolyn sodium (Sodium cromoglicate)	Stabilizes mast cell membranes; inhibits degranulation and histamine release	Lipophobic; no systemic absorption; must be given 3-4x/day; best used prophylactically before allergen exposure; inferior to intranasal corticosteroids
Ketotifen	Mast cell stabilizer + H1 antagonist	Used as eye drops for allergic conjunctivitis

Will not treat symptoms once mast cells have already degranulated
Compliance is difficult due to frequent dosing
Consider in patients who cannot tolerate intranasal corticosteroids
Free of systemic adverse effects (no systemic absorption)

5. Decongestants

Reduce nasal congestion by alpha-adrenergic vasoconstriction; have minimal effect on rhinorrhea, itching, or sneezing.

Oral Decongestants

Drug	Notes
Pseudoephedrine	Alpha-2 agonist; effective; controlled availability (precursor to methamphetamine)
Phenylephrine	Not superior to placebo in clinical trials; not recommended

Side effects: hypertension, insomnia, tachycardia, arrhythmia, anorexia
Often combined with antihistamines (e.g., loratadine + pseudoephedrine)

Topical Decongestants

Drug	Notes
Oxymetazoline	Imidazoline; very effective; rebound congestion (rhinitis medicamentosa) if used >3-5 days
Xylometazoline	Similar to oxymetazoline
Naphazoline	Older agent; significant rebound
Tetrahydrozoline	Primarily used as eye drops

Do not use for more than 3-5 days - risk of rebound congestion (rhinitis medicamentosa)

6. Intranasal Anticholinergics

Drug	Notes
Ipratropium bromide	Decreases watery nasal secretions from seromucous glands; used for rhinorrhea in allergic and non-allergic rhinitis; needs 6x/day dosing due to short half-life

Useful as adjuvant therapy in patients with persistent rhinorrhea despite intranasal corticosteroid use
Combination with intranasal corticosteroids more effective than either alone

7. Systemic Corticosteroids

Used for short courses in severe allergic inflammation only
Prednisone, methylprednisolone, dexamethasone
Oral preferred over parenteral for allergic rhinitis
Not recommended for routine use - largely replaced by intranasal steroids
Effects noticed within 12-24 hours

8. Biologics

Drug	Mechanism	Notes
Omalizumab	Humanized anti-IgE monoclonal antibody	Not FDA-approved for allergic rhinitis; approved for chronic urticaria and asthma; superior to immunotherapy alone when combined; costs ~$18,000/year
Dupilumab	IL-4/IL-13 receptor antagonist	Approved for chronic rhinosinusitis with nasal polyps (CRSwNP)
Mepolizumab / Benralizumab	Anti-IL-5 / anti-IL-5R	Eosinophilic disease; nasal polyps

9. Immunotherapy (Disease-Modifying)

The only treatment that alters the natural course of allergic disease.

Subcutaneous Immunotherapy (SCIT) - conventional allergy shots
Sublingual Immunotherapy (SLIT) - sublingual drops or tablets

"Immunotherapy is the most effective treatment of allergic rhinitis." - Cummings Otolaryngology Head and Neck Surgery

Summary: Hierarchical Treatment Approach

Mild Intermittent AR:
  → Oral/intranasal antihistamine ± decongestant

Moderate-Severe or Persistent AR:
  → Intranasal corticosteroid (FIRST-LINE)
  → Add intranasal antihistamine (most effective combination)
  → Add montelukast if concurrent asthma

Persistent rhinorrhea:
  → Add intranasal ipratropium bromide

Prophylaxis before allergen season:
  → Start INCS 2 weeks early; consider cromolyn sodium

Disease modification:
  → Allergen immunotherapy (SCIT or SLIT)

Severe/refractory/CRSwNP:
  → Biologics (omalizumab, dupilumab)

Sources:

Cummings Otolaryngology Head and Neck Surgery, Chapter 35
KJ Lee's Essential Otolaryngology, Chapter on Treatment of Allergy
Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol 1

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