Jalbani G A, Aamir K, Shaikh A M, Unar M A, Ashraf R, Soomro F M.
To evaluate and compare the effects of first generation anti-histamine (Chlorpheniramine maleate) and second generation anti-histamine (Loratadine) on isolated trachea of rabbit.
J Pak Med Assoc Jan ;54(11):556-61.

Objective: The incidence of respiratory allergy has increased gradually over the past several years and current estimates suggest that allergic rhinitis affects approximately 20% of the population. The purpose of study was to evaluate the antagonistic effects of chlorpheniramine maleate and loratadine on histamine induced contractions in isolated trachea of rabbit and also to compare the effects of first generation anti-histamine (chlorpheniramine maleate and second generation anti-histamine Loratadine). Methods: In this study twenty-four experiments were performed on isolated trachea of rabbit, in the presence of selected standard concentration of histamine dihydrochloride, antagonistic effects of various concentrations of chlorpheniramine maleate (10-18 to 10-3 gm/ml) and loratadine from concentrations 10-18 to 10-3 gm/ml were recorded by Polygraph Model 7B in terms of rate and amplitude. Results: Chlorpheniramine maleate showed non-significant antagonistic effect from concentrations 10-18 to 10e-3gm/ml in case of rate and 10-18 to 10-8 gm/ml in case of amplitude. Significant response showed from concentrations 10-8 to 10-3 gm/ml in case of rate (P<0.001) and 10-7 to 10-3 gm/ml in case of amplitude (P<0.001) while, loratadine showed non-significant response from concentrations 10-18 to 10-12 gm/ml in case of rate and from concentration 10-18 to 10e-14gm/ml in case of amplitude. Significant response observed from concentrations 10-11 to 10-3 gm/ml in case of rate and 10-13 to 10-3 gm/ml in case of amplitude. Conclusion: It was concluded that chlorpheniramine maleate antagonized the histamine induced contractions 80.65% at concentration 10-3 gm/ml in case of amplitude and 11.35% at concentration 10-3 gm/ml in case of rate and loratadine 76.82% in case of amplitude and 10.59% in case of rate (JPMA 54:556;2004).

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