Quantitation of Pyrantel Pamoate in Pharmaceuticals Using Permanganate by Visible Spectrophotometry

Two simple, accurate and precise spectrophotometric methods are developed and validated for the assay of pyrantel pamoate (PP) in pharmaceuticals. The methods employ the oxidative property of potassium permanganate (KMnO₄) in acidic and alkaline conditions. In the first method (method A), PP is converted into its free base, pyrantel (PR), and treated with known excess of KMnO₄ in acidic condition followed by the measurement of unreacted KMnO₄ at 550 nm. Method B is based on the registration of absorbance of green colored chromogen formed due to the reduction of KMnO₄ by PP in alkaline condition. The methods obeyed Beer’s law over a range of 1–20 μg/ml in inverse manner, and 0.75–15 μg/ml for method A and method B, respectively, with apparent molar absorptivity values of 1.05⋅10⁴ and 2.85⋅10⁴ l⋅mol⁻¹⋅cm⁻¹. The optical parameters such as limits of detection (LOD), quantification (LOQ), and the Sandell sensitivity values are also reported. The accuracy and precision of the methods are assessed on intra- and inter-day basis. A recovery study by standard addition procedure is also carried out for further assurance of accuracy. The developed methods are successfully applied to determine PP in tablets. The results are more satisfactory as per current ICH guidelines.