Electrochemical reduction of loprazolam mesilate in an aqueous medium

Abstract

The electrochemical characteristics of loprazolam mesilate have been evaluated in an aqueous solution using dc, ;K, and normal and inverse pulse polarography, as well as cjdic voltammetry and controlledpotenti:il coulometn3. This drug undergoes three different reduction steps. The first, a four-electron mnsfer, corresponds t o the reduction of the nitro group t o give the corresponding hydroxylamine. The second, a two-electron tr:insfer, corresponds t o the reduction o f the azomethine group, either before or after ( i n an acidic solution) h!drol!-sis. The third wave corresponds t o a four-electron transfer in an acidic medium and t o a two-electron transfer in an alkaline medium. In an acidic solution, this third step involves the nvo-electron reduction o f the hydroxylamine group t o the corresponding amine plus the two-electron reduction o f 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 mt';isureiiients o f the ctrug. [ 5-7, 11 1, and flunitrazepam [9,10]. The hydrolysis o f these compounds has also been investigated [9, 12 J. The electrochemical behavior of these compounds has been related to their spectrophotometric characteristics [2, 4, 13, 141 as well as to their pharmacok)gical activity [ 151; structure activity correlations have also been established [ 61. To our knowledge, no physicochemical study o f loprazolam has been reported. Only its pharmacokinetic properties have been determined using a radio receptor assay o f the drug in plasma [lba]. It is a potent hjpnotic agent that does not distort sleep patterns and is free from residual effects the next morning [ lbd]. Possessing both imidazole and nitro substituents, its plasma half-life, ranging from 6 t o 8 hours, is situated between the rapidly eliminated imidazo and triazolo derivatives (alprazolam, triazolam, estazolam) and the slowly eliminated nitrodiazepins (nitrazepam, clonazepam, flunitrazepam, or nimetazepam) [ lbb]. The aim of this work is t o study the electrochemical reductions of loprazolam, and nitrazepam, which are carried out in parallel in order t o obtain a more complete understanding o f the reduction process.

Determination of Copper by Adsorptive Stripping Voltammetry of Its Complex with Adenine

“…This feature, together with the fact that a plateau is observed when the concentration is increased and a constant deposition time is used, indicates that a monolayer is probably formed [37].…”

Electrochemical behavior of a nitrobenzenesulfonyl derivative of aniline in aqueous solution

“…On the other hand, as with other nitroaromatic com pounds [9][10][11][12][13][14] , the over all course of the reduc tion of the N-phenyl-4-nitrobenzenesulphonamide in aque ous so lu tion prob a bly in volves the re duc tion of the nitro group to the hydroxylamine in a four elec tron pro cess. The re sults can be ex plained by a scheme of the gen eral mech a nism for re lated ni tro com pounds [9][10][11][12][13][14] …”