Use of electrophilic coupling reagents, 3-methyl-2-benzothiazolinone hydrazone hydrochloride and 4-amino antipyrine, for the spectrophotometric analysis of vardenafil in tablet dosage forms

Two new spectrophotometric methods (MBTH and AP) are developed for the determination of vardenafil in bulk and in tablet dosage forms. The MBTH method involves oxidative coupling of vardenafil with 3-methyl-2-benzothiazolinone hydrazone hydrochloride in presence of ferric chloride in acidic medium, yielding green colored chromogen with absorption maxima at 625 nm. The AP method is based on the oxidation of 4-aminoantipyrine by potassium periodate, which subsequently couples with vardenafil in an alkaline medium to form a red colored product having absorption maxima at 530 nm. The absorbance concentration graphs were rectilinear over the range of 4-40 μg/ml for MBTH method and 4-60 μg/ml for AP method. The developed methods were fully validated as per the guidelines prescribed by ICH. The application of the proposed methods in the determination of vardenafil in their commercial tablet dosage forms was successful showing good percentage recoveries.Key words: vardenafil, electrophilic coupling agent, MBTH, aminoantipyrine, analysis