Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A-D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, lambda(max) 520 nm) or by oxidizing it with excess N-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: lambda(max) 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: lambda(max) 720 nm) or by the formation of a chloroform-soluble, coloured ion-association complex between the drug and Azocarmine G at pH 1.5 (method D: lambda(max) 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1-10, 2-12, 4-28 and 2.5-25 mu g/ml for methods A-D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within +/-1.0%. Recoveries were 98.9-100.2%.