Simultaneous determination of pilocarpine and isopilocarpine in pharmaceutical preparations by liquid chromatography

A liquid chromatographic assay method is described for the simultaneous determination of pilocarpine and isopilocarpine in pharmaceutical preparations. The method involves separation of the isomers on a high-resolution ion-exchange column, followed by detection of pilocarpine and isopilocarpine by UV absorption in the 217-nm region. The specificity of the method is such that pilocarpine and isopilocarpine can be assayed separately in the presence of one another and in the presence of the excipients commonly found in commercial pilocarpine solutions. Its sensitivity for isopilocarpine is at least 25 ppm (independent of the concentration of pilocarpine). In contrast, USP methods lack both specificity and sensitivity. It is concluded that this method is applicable to the routine analysis of commercial pilocarpine preparations and is an improvement over the official methods.