A new spectrophotometric method for the determination of finasteride in tablets.

A simple, rapid, accurate, precise and sensitive colorimetric method for the determination of finasteride in tablets is described. The proposed methods are based on the formation of ion-pair complexes between the examined drug with bromophenol blue (BPB), bromocresol green (BCG) and bromothymol blue (BTB), which can be measured at the optimum lambda(max). Beer's law is obeyed in the concentration ranges 3.0-15.0, 3.0-15.0 and 5.0-20 microg/mL with BPB, BCG and BTB, respectively. The detection limits of FIN was found to be 1.16 microg/mL for BPB, 1.17 for BCG, 1.76 microg/mL for BTB. All the methods gave similar results and were validated for selectivity, linearity, precision and sensitivity. The proposed methods were directly and easily applied to the pharmaceutical preparation with accuracy, resulting from recovery experiments between 100.11 and 100.33% for BPB, 100.17 and 100.67% for BCG and 100.33 and 100.60% for BTB methods. The low relative standard deviation values indicate good precision and high recovery values indicate accuracy of the proposed methods. The proposed methods have been applied to the determination of drug in commercial tablets. Results obtained from the analysis of commercial preparations with the proposed methods are in good agreement with those obtained with the official HPLC method.