Autoxidation of tetrazepam in tablets: Prediction of degradation impurities from the oxidative behavior in solution

Article abstract of DOI:10.1002/jps.2600810216

The major route of degradation of tetrazepam (1) is oxidation to 7-chloro- 5-(3-keto-cyclohexen-1-yl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one (3) via the stable 7-chloro-5-(3-hydroperoxy-cyclohexen-1-yl)-1,3-dihydro-1- methyl-2H-1,4 benzodiazepin-2-one (2). Minor degradation products are 7- chloro-5-(1,2-epoxycyclohexan-1-yl)-1,3-dihydro-1-methyl-2H-1,4- benzodiazepin-2-one (5) and 7-chloro-1,3-dihydro-1-methyl-2H-1,4- benzodiazepin-2,5-dione (4), resulting from cleavage of the C-C bond between the cyclohexene ring and the benzodiazepine ring. After 48 h, AIBN (2,2'- azobis[2-methyl-propanenitrile]) in acetonitrile at 40 °C produced qualitatively the same impurities as those observed in the stability study of tablets of 1. Other stress tests (thermal stress at 80 °C, heavy metal oxidation, hydrogen peroxide, acid-catalyzed oxidation) caused qualitatively different profiles of degradation.