Diphemanil Methylsulfate

A simple detection system with a high-performance liquid chromatography (HPLC) with positive ionisation-tandem mass spectrometry (ESI-MS/MS) for determining diphemanil methylsulphate (DMS) levels in human plasma using 4-diphemanylmethylene,1-methylpiperidine as an internal standard (I.S.), is proposed. The acquisition was performed with the multiple reactional monitoring (MRM) mode, by monitoring the transitions: m/z 278>262 for DMS and m/z 263>247 for the I.S. The method involved a simple single-step deproteinisation with acetonitrile. The analyte was chromatographed on a Zorbax C18 reversed-phase chromatographic column by isocratic elution with 10(-3)M ammonium acetate and 10(-3)M hexafluorobutyric acid, adjusted to pH 7.0 with ammoniac/acetonitrile (40/60, v/v). The results were linear over the studied range (0.5-50.0 ng mL(-1)) and the total analysis time for each run was 10 min. The mean extraction apparent recoveries expressed at the 95% intervals of confidence were 94-104% for DMS and 92-106% for the I.S. The intra- and inter-assay precisions were 4.6-8.4% and 2.9-10.6%, respectively. The limit of quantification was 0.15 ng mL(-1). The devised assay was successfully applied to the residual concentrations monitoring in infant.

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 1 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 1 and 2, respectively. The stability studies have been performed for 2 and 10 mg DMS tablets subjected at various temperatures: 25 degrees C (long term storage condition) and 40 degrees C (accelerated storage condition) for 18 and 6 months, respectively. At 25 degrees C, the samples were found to be stable for the study period. At 40 degrees C, 2 and 10 mg DMS tablets showed degradation up to 5 and 10% over a 6-month period.