Simultaneous Determination of Cinchocaine Hydrochloride and Betamethasone Valerate in Presence of Their Degradation Products.

Cinchocaine hydrochloride (CIN) and betamethasone valerate (BMV) are co-formulated in pharmaceutical formulations that could be used for local treatment of hemorrhoids. Both drugs are susceptible to hydrolytic degradation. Two sensitive and precise stability-indicating chromatographic methods were developed for the simultaneous determination of both active pharmaceutical ingredients. The developed methods were applied for quantitation of CIN and BMV in their pure forms, in presence of their corresponding degradation products and in their pharmaceutical formulation. The first method was a high performance liquid chromatographic (HPLC) one, separation and quantitation was achieved using a Waters Spheriosorb® 5 µm ODS2 C18 analytical column and an isocratic mobile phase formed of acetonitrile-acetate buffer (pH 6.5 ± 0.1) in a ratio of (55:45, v/v). The mobile phase was pumped at a flow rate of 1.2 mL/min. UV-detection was done at 240 nm using photodiode array detector. The second method was based on thin layer chromatography (TLC) fractionation coupled with densitometric determination. Separation was done on high performance thin layer chromatography (HPTLC) silica gel 60F254 plates using a developing system formed of chloroform-toluene-ethanol-acetic acid in a ratio of (4.5:4.5:1:1, by volume). The separated bands were scanned densitometrically at 240 nm. For the HPLC method, linearity was confirmed over concentration ranges of 4-300 and 4-350 µg/mL for CIN and BMV, respectively. For the HPTLC-densitometric method, the obtained ranges were 0.5-12 and 0.5-10 µg/band for CIN and BMV, respectively. The developed methods were optimized and validated according to the ICH guidelines. CIN acid degradation products were separated and identified by mass spectroscopy. The developed HPLC method was used to study the kinetics of acid and alkali degradation of the both drugs. The results obtained were statistically analyzed and compared with those obtained by applying the official methods for both drugs.