Cyclodextrin-modified micellar electrokinetic chromatography for the analysis of Esterom®, a topical product consisting of hydrolyzed benzoylecgonine in propylene glycol

Esterom(R), a new drug currently in human clinical trials, is a mixture of compounds in a propylene glycol vehicle. It is being evaluated as a topical treatment to aid in the relief of muscle pain and to increase range of motion. Benzoylecgonine is the major component of Esterom and there are at least nine other minor constituents, including four hydroxypropyl esters that have multiple diasteriomers. The aim of the study was to develop a capillary electrophoresis method for the simultaneous separation of the main components in Esterom, including the multiple proposed diastereomers of the esters. Due to the complex sample composition, the use of micelles and cyclodextrins as buffer modifiers was evaluated. A cyclodextrin-modified micellar electrokinetic chromatography method was able to determine 7 of the 8 UV-active Esterom components, with baseline separation of 7 of the 10 diastereomers of the hydroxypropyl esters.