A Comparative Study of the Quality of Diltiazem and Verapamil Manufactured in Mexico Versus Those Manufactured in the United States

Abstract

Objective: To determine whether or not the amount of active ingredient and content uniformity of diltiazem and verapamil products manufactured in Mexico are comparable to those manufactured in the U.S. Methods: High-performance liquid chromatography (HPLC) assay was used to compare the quantity of active ingredients contained in diltiazem 120 mg ER capsules and verapamil 120 mg ER tablets manufactured in Mexico vs. those manufactured in the United States. The content uniformity was also compared using guidelines contained in the U.S. Pharmacopoeia-National Formulary (USP- NF), with guidelines slightly modified to better suit the experiment. The acceptable range of variances in the quantity of active ingredient was taken from the USP-NF (90-110%). The mean active drug content from the samples manufactured in the U.S. was assumed to meet USP-NF standards at 100%. Results: The experimental results showed that the Mexican verapamil 120 mg ER capsules fell below the USP-NF acceptable range of 90-110% with a value of 83.2%, which is 11.2% less than the U.S. samples tested. The content uniformity of Mexican verapamil also fell below the USP-NF acceptable range of 90-110% with a value of 88.6%. The Mexican diltiazem 120 mg ER capsules fell above the USP-NF acceptable range of 90-110% with a value of 196.2%. The content uniformity was also above the acceptable range with a value of 183.0%. Conclusion: The results of this study showed that the drugs used in this experiment are not within the range that is deemed acceptable by USP-NF standards. The Mexican verapamil was below the range deemed acceptable while the Mexican diltiazem was above the range deemed acceptable. However, the study results cannot be generalized since they represent only a limited number of batches.