RGB-evaluated determination of finasteride in the presence of its pharmacopeial impurity

Finasteride hydrochloride (FIN), used for the management of benign prostatic hyperplasia, is highly unstable. In order to determine FIN in the presence of its closely related impurity, reported in its British Pharmacopoeia monograph, (methyl-3-oxo-4-aza-5α-androst-1-ene-17β-carboxylate) (IMP) and in pharmaceutical formulation, the objective of this work was to design and validate two stability-indicating methods. The first method is the TLC-densitometric technique where good separation between FIN and IMP was achieved using a developing system composed of toluene: methanol: triethylamine (9: 1.5: 0.8, v/v/v) and UV detection at 237 nm. In the second method, the first derivative ratio spectrophotometric (1DD) technique was carried out and the amplitude of the minimum at 238.6 nm was used for the determination of FIN over the concentration range of 20-120 μg mL-1. Method validation was performed in agreement with ICH guidelines. The suggested methods were successfully applied to a pharmaceutical dosage form. The accuracy and precision of the two created methods and the reference method did not differ significantly, according to statistical analysis of the results. The developed techniques can be used in quality control laboratories to analyze FIN because they are sensitive and selective. Only sustainability assessment using AGREE favored the spectrophotometric method due to limited use of organic solvents. While, performance and practicality assessments (RAPI and BAGI) demonstrated that the new approaches were equally valuable and efficient analytical techniques.