• H₁ antihistamines:
  •  for treating:
    • nasopharyngeal itching
    • sneezing
    • watery rhinorrhea
    • ocular: itching, tearing, erythema
  •  Side effects:-- older H₁ antihistamines:
    • sedation
    • visual disturbance
    • urinary retention
    • arrhythmias
• Newer H₁ antihistamines:( terfenadine (Seldane) astemizole (Hismanal))
  • Less sedating (reduced ability to cross the blood brain barrier)
  •  Important drug-drug interactions:
    • macrolide antibiotics (e.g. erythromycin, clarithromycin (Biaxin)), ketoconazole-class broad-spectrum antifungal drugs, inhibit terfenadine (Seldane) or astemizole (Hismanal) metabolism.
    • Toxic levels of terfenadine (Seldane) or astemizole (Hismanal) may induce potentially fatal cardiac arrhythmias.
    • These new H₁ antihistamines are contraindicated for concurrent use with macrolide antibiotics and ketoconazole-class and fungal drugs or in the presence of impaired hepatic function or inpatients predisposed to arrhythmias.

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• Topical alpha-adrenergic agonists:
  • Phenylephrine (Neo-Synephrine) or oxymetazoline (Afrin) reduce nasal congestion/obstruction.
    • Efficacy duration: limited due to rebound rhinitis and systemic effects:
      1. insomnia
      2. irritability
      3. hypertension (seen more commonly with oral alpha adrenergic agonists

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•  Oral alpha-adrenergic agonists: -- useful
  • diminishes antihistamines caused sedation
  • enhances antihistamine efficacy in relieving congestion

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•  Cromolyn sodium:
  • liquid, nasal metered-dose spray:
    • no side effects
    • prophylactic use
      • reduces episodic allergen nasal mast cell activation
    • equal efficacy: cromolyn sodium and nonsedating antihistamines

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• Intranasal glucocorticoids:
  • most potent drugs available for management of established rhinitis (seasonal or perennial) and including vasomotor rhinitis
    • topical-to-systemic activity greater for: flunisolide (AeroBid) or budesonide (Rhinocort), compared to beclomethasone (Banceril) or triamcinolone (Aristocort).
  • same efficacy, reduced side effects, compared to same agent administered orally
  •  Side effects:
    • local irritation (most frequent)
    • Candida over growth (unusual)
  • Topical high potency glucocorticoids: -- superior efficacy compared antihistamines during pollen season.

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• Immunotherapy (hyposensitization)
  • based on repeated, subcutaneous injections of gradually increasing allergen (specific for the symptom complex)
  • Duration: 3-5 years
  •  Contraindications:
    • significant cardiovascular disease
    • unstable angina
  • Cautious use:
    • patients receiving beta adrenergic blockers (due to difficulty in managing possible anaphylactoid responses to treatment)
  • Clinical Management Sequence:
    1. identification of allergens confirmed by allergens-specific IgE skin testing and/or serum assay.
    2. Avoidance of offending allergen
    3. Mild symptoms: prophylaxis with topical cromolyn sodium or single (bedtime) dose of  chlorpheniramine (Chlor-Trimeton)or astemizole (Hismanal) or terfenadine (Seldane) (decision based on side effects and presence of other concurrent medications or disease.
    4. Prominent symptoms: Topical beclomethasone (Banceril) or if needed budesonide (Rhinocort) or flunisolide (AeroBid)
    5. Management failure: immunotherapy

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