Hydroxyzine
Hydroxyzine is a piperazine derivative with antihistamine, antiemetic, and anxiolytic properties. Hydroxyzine's antihistaminic effect is due to its metabolite, cetirizine, a potent H1 receptor antagonist and selective inhibitor of peripheral H1 receptors. This agent competes with histamine for binding at H1-receptor sites on the effector cell surface. The sedative properties of hydroxyzine occur as a result of suppression of certain subcortical regions of the brain. Secondary to its central anticholinergic actions, hydroxyzine may be effective as an antiemetic.