Physicochemical Equivalence and Validation of an HPLC Analytical Method for the Quantification of Glibenclamide and Its Sulfonamide Impurity in Prescribed Glibenclamide Tablets in Nigeria

Objective: To investigate the physicochemical equivalence of four brands of commercially available glibenclamide tablets in Nigeria and to develop a validation method using HPLC for the quantitative determination of glibenclamide and its sulfonamide impurity present in these tablets.

Methods: Uniformity of weight, friability tests, hardness/crushing strength, dissolution, and disintegration tests were carried out on tablets/drug samples of each brand. Their functional groups were determined and compared with pure glibenclamide sample (reference standard) using Fourier Transform Infrared Spectroscopy (FTIR) between a range of 4000cm-1 to 400cm-1. High-Performance Liquid Chromatography (HPLC) was used to determine the percentage of glibenclamide and its sulfonamide impurity present in each tablet brand.

Results: From the physicochemical evaluation of the four brands of glibenclamide tablets tested, the brands passed all the British Pharmacopeia specifications, but they all failed the hardness/crushing strength tests and one of the brands failed the assay test requirement for drug content. The developed HPLC method had a percentage recovery between the acceptable limit of 95-105% with percentage relative standard deviation (%RSD) of < 3% while the precision of the method was 0.102% and 0.383% for glibenclamide and its sulfonamide impurity, respectively. The Limit of Detection (LOD) and Limit of Quantification (LOQ) of the developed analytical method for the four brands were 0.075µg/ml and 0.227µg/ml for glibenclamide while that of sulfonamide impurity were 0.114µg/ml and 0.345µg/ml, respectively. In addition, the percentage impurity of sulfonamide in all the brands was less than the acceptable limit of 1%.

Conclusion: The results from the physicochemical evaluation of the glibenclamide brands justified the need for constant monitoring of marketed drug products. The results obtained from the HPLC quantification method developed for this study show that our data is reproducible based on the linearity, precision, and accuracy of data generated for glibenclamide and its sulfonamide impurity in the four brands of glibenclamide tablets prescribed to DM patients in Nigeria, which were judged to be satisfactory at the time of this study.