Antihistamines for the Treatment of Allergic Rhino-conjunctivitis

Abstract

Histamine plays an important role in the pathogenesis of allergic rhino-conjunctivitis (ARC). First generation antihistamines are sedative, they cause cognitive and psychomotor impairment, and they are not indicated for the treatment of ARC. Second generation H1-antihistamines, with their improved safety profile and faster and longer duration of action, meet many of the ARIA (Allergic Rhinitis and its Impact on Asthma) optimal antihistamine prerequisites for the treatment of ARC. They are recommended as first line therapy for the treatment of children and adults with ARC and are efficacious in rapidly reducing itching, sneezing and rhinorrhoea. However, they offer suboptimal relief to patients with significant nasal congestion. They are available as oral, intranasal and ocular preparations. Oral preparations are more effective when used continuously and have demonstrated a greater or similar efficacy to leukotriene receptor antagonists (LTRA), with a potentiated effect when used simultaneously. Second generation H1-antihistamines are recommended for both intermittent and persistent ARC and in combination with intranasal steroids (INS) for severe disease. Intranasal H1-antihistamine preparations have the advantage of being delivered directly to the nasal mucosa with faster onset of action (15 vs 60 min) and may be preferable when rapid symptom relief is desirable or for on-demand therapy. They are recommended for mild/intermittent disease. A better outcome is achieved when used in combination with INS. In particular, a single formulation of fluticasone with azelastine nasal spray has demonstrated superiority to monotherapy with either compound in patients with moderate/severe disease. Its use is recommended when monotherapy has proven insufficient and for the treatment of moderate/persistent disease. Ophthalmic preparations are efficacious in ameliorating ocular symptoms and can be used when oral antihistamines fail. In the management of ARC, second generation H1-antihistamine treatment reduces symptoms, improves quality of life, lessens the overall burden of disease and reduces disease-associated costs.