Electroreduction of the muscle relaxant drug dantrolene sodium at the mercury electrode and its determination in bulk form and pharmaceutical formulation.

The electroreduction of the muscle relaxant drug dantrolene sodium at the mercury electrode has been studied in the Britton-Robinson universal buffer of pH 2.5-11.5 containing 20% (v/v) methanol by means of dc-polarography, cyclic voltammetry and controlled-potential coulometry. Its reduction took place via three irreversible cathodic steps in solutions of pH < or =6, two steps in solutions of 6<pH<10 and a single step at pH values > or =10 through the consumption of 10, 8 or 4 electrons, respectively. This behavior was attributed to the reduction of NO(2) group (1st and 2nd steps at pH < or =6 or the single step at pH > or =10) and the -CH=N- double bond (3rd step at pH <10). Two polarographic procedures (direct current and differential-pulse modes) and three adsorptive cathodic stripping voltammetric procedures (linear-sweep, differential-pulse and square-wave modes) were described and successfully applied for quantification of dantrolene sodium in its bulk form and in pharmaceutical formulation (Dantrolex tablets).