Guanabenz degradation products and stability assay.

Guanabenz, [(2,6-dichlorobenzylidene)amino]guanidine, acetate was shown to be the E-isomer. It decomposed to form the Z-isomer, 2,6-dichlorobenzaldehyde, aminoguanidine, and 2,6-dichlorobenzaldehyde semicarbazone. A stability-indicating assay for the intact drug in the presence of all of its decomposition products by the use of UV spectroscopy is presented.