STUDY RATIONALE

H1 receptor antagonists are main stay of therapy for allergic diseases such as chronic idiopathic urticaria, allergic rhinitis, allergic conjunctivitis. These diseases are evoked by common pathological mechanism characterized by release of histamine and other inflammatory mediators. First generation H1 receptor antagonists like chlorpheneramine , diphenhydramine hydroxyzine and promethazine have not been considered ideal antihistaminics as they cause significant sedation and may produce some anticholinergic side effects which may be harmful to the patients. Second generation antihistaminics like cetirizine, levocetirizine, loratadine, fexofenadine, astemizole, terfenadine, mizolastine, ebastine, rupatadine, olopatadine etc have higher H1 selectivity. Therefore, they do not have anticholinergic side effects. These groups of drugs also have no CNS depressant activity. They also have some additional antiallergic activity by inhibiting late phase of allergic reaction by acting on leukotrines or by antiplatelet activating factor. [2]

Rupatadine is a novel selective long acting histamine H1 receptor inverse agonist (H1 antihistamine), which is currently approved as a once daily dose of 10milligram, for the treatment of allergic rhinitis and chronic idiopathic urticaria. Rupatadine has shown to have a higher affinity for the H1 receptor than fexofenadine and levocetirizine. It has both antihistaminic and anti-platelet activation factor (PAF) property. It may produce side effects like headache, sleepiness, fatigue, dry mouth, dyspepsia . [3]

Oloaptadine is a selective histamine H1 receptor-antagonist having inhibitory effects on the release of inflammatory lipid mediators such as leukotrienes, thromboxane, platelet-activating factor (PAF), etc, from human polymorphonuclear leucocytes and eosinophils. It also inhibits the tachykininergic contraction in the bronchi of the allergen model by prejuntional inhibition of peripheral sensory nerves. [4] Olopatadine is recently approved for the treatment of chronic idiopathic urticaria. It has additional advantage over other drugs that it inhibits the release of inflammatory lipid mediators like leukotrienes, thromboxane, platelet-activating factor (PAF).

In recent years, treatment of CIU has changed from levocetirizine to rupatadine and olopatadine. Current treatment of CIU comprises of either these drugs used for 1 to 3 months duration. Research has been attempted to find the best drug for CIU focusing on efficacy and safety data. Indian population being commonly affected by CIU, patients has poor affordability for the most efficacious drug for treatment of CIU. Hence, it was decided to study and compare two drugs- the currently considered medicine of choice rupatadine, and the most recently introduced olopatadine in the local population of Central India. Therefore, aim of present study is to provide better and improved treatment option for CIU based on cost effectiveness, efficacy, and safety profile.