Spectrophotometric Analysis of Dutasteride in Pure and Tablet Dosage Forms

Four simple and sensitive visible spectrophotometric methods have been developed for the assay of dutasteride. Method I describes the interaction of dutasteride, as an n-electron donor, with chloranil, as a pi-acceptor, in acetonitrile to give reddish orange colored chloranil radical anion with absorption maxima at 525 nm. Method II involves the oxidative coupling reaction of dutasteride with 3-methyl-2-benzothiazolinone hydrazone hydrochloride in the presence of ferric chloride in an acidic medium, which results in a green colored product with absorption maxima at 550 nm. Methods III and IV are based on the formation of ion-pairs of dutasteride with bromothymol blue and bromophenol blue, which are extracted into chloroform and exhibit absorption maxima at 425 (bromothymol blue) and 435 nm (bromophenol blue). Regression analysis of Beer’s law plot showed good correlation in the concentration range of 2–40, 1–20, 5–50, and 2–20 μg mL for Methods I, II, III, and IV, respectively. Different variables affecting the reaction were studied and the experimental conditions were optimized. The proposed methods were applied successfully to analyze dutasteride in tablets dosage forms. No interference was observed from common pharmaceutical excipients.