Interaction Studies of Fexofenadine: Drug Interaction, Complexation, Derivative Chemistry, Antihistaminic and Anticholinergic Activities

Fexofenadine is the major metabolite of terfenadine, but its pharmacokinetics differs from that of terfenadine, it is eliminated from the liver into bile in unchanged form. The aim of the present work is to study the availability of fexofenadine in presence of antacids, H2-receptor antagonists, quinolones, metformin hydrochloride. Owing to these interactions, metal complexes of fexofenadine were synthesized with various essential and trace elements like magnesium, calcium, chromium, manganese, iron, nickel, copper, zinc and cadmium. In order to study its structure activity relationship derivatives of fexofenadine were synthesized with various compounds. Metal complexes and synthesized compounds were characterized by their physical parameters and with spectroscopic techniques like AA, CHN, FT-IR, 1H-NMR, UV and mass spectra. The synthesized derivatives of fexofenadine were subjected to antihistaminic and anticholinergic activity studies on guinea pig ileum and compared with the reference drug. These compounds exhibited antihistaminic and spasmolytic activity but not anticholinergic activity observed from their EC50 values. All these activities were dose dependent in nature.