Determination of Rufinamide in the Presence of 1-[(2,6-Difluorophenyl)Methyl]-1H-1,2,3-Triazole-4 Carboxylic Acid Using RP-HPLC and Derivative Ratio Methods as Stability Indicating Assays to Be Applied on Dosage Form

Background: Rufinamide is a triazole derivative that is structurally dissimilar to other marketed antiepileptic drugs, has been assumed a marketing authorization, by the European Union and FDA, for use as a complementary therapy for seizures associated with Lennox-Gastaut syndrome. Objective: This work is concerned with development of two methods for determination of rufinamide (RUF) in presence of 1-[(2,6-difluorophenyl)methyl]-1H-1,2,3-triazole-4 carboxylic acid as its alkaline degradation product in dosage form. Methods: The first method was capable of determing RUF in the presence of its alkaline degradation product and in dosage form. Kromasil C-8 column and mobile phase consisting of acetonitrile-water (50:50, v/v) were used and UV detection at 210 nm. In the second method, first derivative ratio spectrophotometry, RUF was determined by measuring peak amplitude at 269.5 nm over 5-30 mu g/mL. Results: The linearity range of RUF was 10-90 mu g/mL for HPLC method covering its therapeutic range with r(2) = 0.9999. Forced degradation under alkaline conditions was carried out, the degradation product was isolated and its structure was confirmed. Both methods were validated in accordance to ICH guidelines. Statistical analysis revealed no significant difference between obtained results and reported ones. Conclusion: The present study is useful for therapeutic drug monitoring and routine analysis of RUF in quality control laboratories. Highlights: Kinetics of the alkaline degradation of RUF was studied by following the concentration of the remaining drug until complete degradation was achieved.