Degradation profile and identification of the major degradation products of dobupride under several conditions by GC/MS and HPLC-particle beam/MS

The effect of pH, LIGHT, temperature and oxygen on the stability of dobupride (1), a novel gastroprokinetic drug, has been studied, storing the sample in the solid state and as a solution in methanol-water. The main forced degradation products have been identified by means of techniques such as GC/MS and HPLC-particle beam/MS, and two major degradation pathways have been characterized. One degradation route involves the loss of chlorine, yielding 4-amino-2-butoxy-N-[1-(1,3-dioxolan-2-ylmethyl)piperid -4-yl]benzamide (4) as the major degradation product. The second pathway results from cleavage of the piperidine-amide bond, producing 4-amino-2-butoxy-5-chlorobenzamide (2) as the major degradation product. Under the studied conditions, except when exposed to direct LIGHT in solution, dobupride has been shown to be very stable: after 5 months storage, the benzamide 2 (second pathway) was the only product identified (less than 0.5%). However, when dobupride in solution is exposed to natural or artificial sunlight, degradation is very fast, and after 7 days only 5% of the unchanged product remains. Under these circumstances, the main degradation route is the first one, with compound 4 being the most abundant degradation product, and compound 2 only being detectable in small amounts.