Development and Validation of IndirectVisible Spectrophotometric Method for Doxepin and Dothiepinin Pureandthe Tablet Dosage Forms

The aim of the present work is to develop a simple, sensitive, accurate and rapid visible spectrophotometric method for the quantitative estimation of doxepin and dothiepin in both pure and tablet dosage forms. The developed method is based on the oxidation of DOX and DOT by Ce(IV)inan acid medium followed by reactingit with leuco crystal violetto form a violetcoloreddye which showed absorption maxima (λmax) at 590 nm. Beer s law was obeyed in the concentration range of 0-60μg mL-1in both the drugs. The recovery ranged from 99.26-100.02% for DOX and from 99.64 – 100.36% for DOT. The regression coefficient was found to be 0.998 and 0.996for DOX and DOT,respectively.The limits of detection (LOD) and quantification (LOQ) values are calculated according to ICH guidelines. The method developed was successfully applied for the determination of DOX and DOT in dosage forms.