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A modification of the USP HPLC method [ United States Pharmacopeia XXII, pp. 1444-1446] for the assay of the purity of verapamil hydrochloride has been evaluated for the determination of the drug content and related compounds in drug raw material. The method enables the resolution of 16 related compounds from the parent drug and, in most cases, from each other. The minimum quantifiable amount for most related compounds is less than 0.05%. Six drug raw material samples are analysed and the total impurities found to be 0.3% or less. All drug assay values were within the USP recommended limits of 99.0-100.5%.

A high-performance liquid chromatographic (HPLC) method has been developed for the determination of famotidine and related compounds in drug raw materials and formulations. The minimum detectable amount of the available related compounds is less than 0.02% and the minimum quantifiable amount is less than 0.1%. Famotidine impurity levels were between 0.5 and 2.5% in raw materials. 0.44% in one tablet sample and about 3% in an IV solution, allowing for stabilizers.