ELECTROCHEMICAL REDUCTION OF LOPRAZOLAM MESILATE IN AN AQUEOUS-MEDIUM

The electrochemical characteristics of loprazolam mesilate have been evaluated in an aqueous solution using dc, ac, and normal and inverse pulse polarography, as well as cyclic voltammetry and controlled‐potential coulometry. This drug undergoes three different reduction steps. The first, a four‐electron transfer, corresponds to the reduction of the nitro group to give the corresponding hydroxylamine. The second, a two‐electron transfer, corresponds to the reduction of the azomethine group, either before or after (in an acidic solution) hydrolysis. The third wave corresponds to a four‐electron transfer in an acidic medium and to a two‐electron transfer in an alkaline medium. In an acidic solution, this third step involves the two‐electron reduction of the hydroxylamine group to the corresponding amine plus the two‐electron reduction of the double bond between N‐methylpiperazine and the imidazol group. In an alkaline solution, only the latter reduction takes place. Such behavior holds promise for analytical measurements of the drug. Copyright © 1990 VCH Publishers, Inc.