Spectrophotometric, Spectrofluorometric and HPLC Determination of Desloratadine in Dosage Forms and Human Plasma

Abstract

Four sensitive, simple and specific methods were developed for the determination of desloratadine (DSL), a new antihistaminic drug in pharmaceutical preparations and biological fluids. Methods I and II are based on coupling DSL with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.6 where a yellow colored reaction product was obtained and measured spectrophotometrically at 485 nm (Method I). The same product could be measured spectrofluorometrically at 538 nm after excitation at 480 nm (Method II). Methods III and IV, on the other hand, involved derivatization of DSL with 2,4-dinitrofluorobenzene (DNFB) in borate buffer of pH 9.0 producing a yellow colored product that absorbs maximally at 375 nm (Method III). The same derivative was determined after separation adopting HPLC (Method IV). The separation was performed on a column packed with cyanopropyl bonded stationary phase equilibrated with a mobile phase composed of acetonitrile-water ( (Method IV). The four developed procedures were applied for the determination of DSL in tablets without any interference from the excipients. A low LOQ is a common requirement to support a clinical development program and when this is coupled with a simple procedure for sample preparation and feasible analytical tool, they would be the requirements of an optimized analytical method. Although the previously reported methods that were applied in pharmacokinetic studies of desloratadine possess the required low LOQ, they lack the simple sample preparation and method feasibility that were obtained in our spectrofluorometric method using NBD-Cl as a derivatizing agent where a low LOQ of 0.012 mg/ml was attained which allowed the analytical determination of DSL in spiked and real human plasma. ExperimentalMaterials and Reagents All chemicals were of analytical reagent grade. Desloratadine reference standard was kindly provided by ScheringPlough Corporation, U.S.A. Aerius tablets labeled to contain 5 mg DSL per tablet were purchased from commercial sources at a local pharmacy. Plasma samples were obtained from Mansoura University Hospital, Mansoura, Egypt, and were kept frozen until use after gentle thawing. Sep-Pak ® C18 solid phase extraction cartridges, 200 mg (SPE) were purchased from Waters Corporation (Milford, MA, U.S.A.). 4-Chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) was purchased from Sigma (St. Louis, MO, U.S.A.). A stock solution containing 2 mg/ml was freshly prepared in methanol. 2,4-Dinitrofluorobenzene (DNFB) was also purchased from Sigma (St. Louis, MO, U.S.A.). A stock solution containing 0.25% (v/v) was freshly prepared in methanol. Borate buffer solutions (0.2 M) were prepared by mixing appropriate volumes of 0.2 M boric acid and 0.2 M NaOH and adjusting the pH to 7.6 and 9.0 using a pH meter.29) Formic acid 85%, acetonitrile and methanol; AR Grade, Aldrich (St. Louis, MO, U.S.A.).Apparatus A Shimadzu UV-Visible 1601 PC spectrophotometer was used for the spectrophotometric measurements (P/N 206-67001). The recording range was 0-1.0.The f...

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