Determination of diphenoxylate hydrochloride and atropine sulfate in solutions and tablets

Methods for the determination of diphenoxylate hydrochloride and atropine sulfate combinations in solutions and powdered tablet composites are presented. A semiautomated assay for diphenoxylate hydrochloride in individual tablets (content uniformity) also is presented. The USP XIX assays for these products are cumbersome and, in the case of solutions, inaccurate due to spectral interferences; the proposed methods offer substantial improvements in sensitivity, specificity, and speed. Results obtained by the USP and proposed methods are compared for several lots of commercial products. The accuracy and precision of the proposed methods are shown by standard recovery studies.