In Vitro Antihistaminic Activity of Some 1-Substituted Imidazoles: H2-Receptor Antagonism

Cimetidine is the prototype antiulcer drug having the imidazole nucleus and acts by blocking histamine H2 receptors. Keeping this context in mind, an attempt has been made to study the antihistaminic activity of some novel 1-substituted imidazole derivatives on isolated guinea pig atria to reveal their desired pharmacological effects. In the present revision, some 1-substituted Imidazoles (1a-1d, 2a-2d) were synthesized and confirmed by their FTIR, HNMR, MASS and Elemental spectral data. Antagonistic activity of all prototypes were tested in this bioassay at various concentrations (10, 50 and 100 μg/ml), and concentration-response curves were plotted to check their ability to reverse the activity of Histamine on prior contact with the atria the results have been compared with standard Ranitidine. All the compounds were producing a competitive antagonistic action at 10μg/ml and at higher concentrations (50 and 100 μg/ml) the curves shifted to the right showing maximum inverse agonistic activity which is probably mediated through H2-receptors.