Evolution, Mechanism of Action, and Clinical Applications of Three Generations of Antihistamines

This review explores the development and clinical use of three generations of antihistamines. Initially, antihistamines were developed by understanding the role of histamine in allergic reactions, leading to the creation of drugs that block H1-histamine receptors. First-generation antihistamines, while effective, have non-selective activity and cause sedation. In contrast, second- and third-generation antihistamines are more selective for peripheral H1 receptors, resulting in fewer side effects. Third-generation drugs, as active metabolites of the second generation, offer the highest efficacy and safety. First-generation antihistamines are used for acute allergic reactions, while the latter generations are preferred for treating seasonal and chronic allergic rhinitis. The study's findings are valuable for clinical allergists.