Development and validation of a stability indicating liquid chromatographic method for the analysis of rufinamide bulk material and dosage forms

Abstract

Rufinamide is a triazole anti-epileptic used together with other medications/therapies in the management of seizures linked to Lennox Gastaut Syndrome (LGS) and various epileptic disorders in adults, as well as in children above four years of age. Rufinamide is classified as an orphan drug by the World Health Organization. Currently, rufinamide dosage forms like tablets and suspension are available in the United States and European Union markets. Kenya and other East African countries have to import rufinamide products from these markets. Therefore, there is need to ensure local production of good quality generic rufinamide dosage forms for use by the East African population suffering from LGS. Liquid chromatography is the analytical procedure of choice for the analysis of rufinamide. The current published methods have various drawbacks including the fact that a majority of them are not stability indicating. In the current study, an isocratic, specific, precise, robust, sensitive and accurate reversed phase high performance liquid chromatographic method was developed for the analysis of rufinamide both in bulk material and dosage formulation. The effect of chromatographic factors were investigated in the process of method development through use of inorganic buffer, ion-pairing agent, organic modifier, pH modification and temperature variation. A Phenomenex Hyperclone BDS C-18 chromatography column 250 mm and 4.6 mm dimensions, particle size of 5 μm maintained at a temperature of 35 °C was used. Methanol-0.1 M octane sulphonic acid-0.1 M dipotassium hydrogen phosphate pH 6.5-water (30:10:5:55, % v/v/v/v) mobile phase composition delivered at a flow rate of 1.0 mL/min was used. The pH of the mixture of buffer and ion pairing agent was brought to 6.5 using an equimolar solution of 0.1 M ortho-phosphoric xvii acid. The analytes were detected by ultra-violet absorption spectroscopy at 210 nm wavelength. Rufinamide retention time was found to be about 9.4 min. The developed method was validated using the International Conference on Harmonization guidelines. The parameters investigated include linearity, range, sensitivity, precision, accuracy, specificity and robustness. Method validation showed that it exhibited good linearity over the 50% to 150% range of the analytical concentration with a linear regression coefficient (r2 value) of 0.9997. The detection limit and quantitation limit were found to be 7.81 μg and 15.53 μg, respectively. The method exhibited good precision with the same day analysis coefficient of variation of 0.96% while different day analysis coefficient of variation of 0.64%. The developed method was applied in analyzing five samples, one of them being a commercial sample, Inovelon®, obtained from the United Kingdom market and the other four locally formulated tablets in the Department of Pharmaceutics and Pharmacy Practice of the University of Nairobi. Results obtained indicated that the samples complied with the United States Pharmacopeia 2015 specifications for the assay of rufinamide tablets. From the assay data, the developed method may be utilized and adopted for routine quality analysis of rufinamide dosage formulations. It can also be used in stability studies by the pharmaceutical industry and drug regulatory authorities in assuring a high quality of rufinamide in the market. The method can also find application in monitoring the quality of rufinamide products during post market surveillance.