Identification of the molecular structure of the phenolic primary metabolite of dimetindene in animals and man
De Graeve, J.; Van Cantfort, J.; Gilard, P.; Wermeille, M.M.
Arzneimittel-Forschung 39(5): 551-555
1989
ISSN/ISBN: 0004-4172 PMID: 2569307 Document Number: 329503
The metabolic pathway of dimetindene (dimetindene maleate, Fenistil), an antiallergic drug commercially available for more than 20 years, has remained unknown. By means of HPLC, GC-MS and MS-MS, dimetindene was found to be hydroxylated on the indene moiety of the molecule both in vitro with hepatic microsomes of several species and in vivo in man. Cochromatographic analysis (HPLC and GC-MS) of the primary metabolites produced in vitro and in vivo demonstrated their similarities but revealed differences from the chemically synthesized 5-hydroxy-dimetindene. Using large volumes of in vitro incubations of rat microsomes with dimetindene and cofactors, 1.15 mg of pure primary metabolite were first produced and then extensively purified. The study of the NMR proton in one and two dimensions (COSY) clearly demonstrated that this metabolite is hydroxylated on the C6 of the indene moiety as compared to the C5 for the synthetic product.