Development and validation of stability indicating high-performance liquidchromatographic assays for ketotifen in aqueous and silicon oil formulations

A simple and specific high-performance liquid chromatographic (HPLC) method for the analysis of ketotifen in aqueous solutions and silicon oil suspens ions is described. The HPLC system is based on a reversed phase mu Bondapak C-18 (30 x 0.39 cm) column with a mobile phase of phosphate buffer (0.001 M, pH 7.4):methanol: acetonitrile: trimethylamine (29.8:45:25:0.2, by volum e) at a flow-rate of 1 mL min(-1). The eluent was monitored by UV absorptio n at 299 nm. Silicon oil-based samples were extracted with HCl (0.05 M) usi ng imipramine as internal standard. The recovery of ketotifen and imipramin e was greater than 80 %. The calibration curves for both assays were linear over the ranges examined, yielding correlation coefficients greater than 0 .997. The assay was shown to be stability indicating by subjecting solution s of ketotifen in phosphate buffer to heat, oxidative stress and irradiatio n with ultraviolet light (254 and 369 nm) for up to 8 h. The methodology wa s also shown to be applicable for the analysis of ketotifen in simple aqueo us based formulations, in suspension in silicon oil and for the analysis of samples derived from in vitro skin transfer experiments.