LC determination of diphemanil methylsulfate: application to stability study of stored pharmaceutical formulations

Diphemanil methylsulfate (DMS) is a synthetic antimuscarinic agent classically used in infants for vagal hypertonia-related symptoms. A normal-phase, isocratic liquid chromatographic method was developed for the quantitative determination of DMS in bulk drugs and in pharmaceutical forms. The method has been completely validated and robustness of this method has been studied. The limit of detection (LOD) for DMS impurities namely, impurity I and 2 were found to be 11 and 46 ng/ml. The limit of quantitation (LOQ) was found to be 49 and 139 ng/ml for impurity I and 2, respectively. The stability studies have been performed for 2 and 10 mg DMS tablets subjected at various temperatures: 25 degreesC (long term storage condition) and 40 degreesC (accelerated storage condition) for 18 and 6 months, respectively. At 25 degreesC, the samples were found to be stable for the study period. At 40 degreesC, 2 and 10 mg DMS tablets showed degradation up to 5 and 10% over a 6-month period. (C) 2002 Elsevier Science B.V. All rights reserved.