Identification of Degradation Products in a Phenylbutazone Tablet Formulation

Two previously reported but unidentified phenylbutazone degradation products were isolated from a tablet that was stored at 60° for 203 days. The compounds, α-(N-phenylcarbamoyl)-N-caproylhydrazobenzene and α-hydroxy-α-(N-phenylcarbamoyl)-N-caproylhydrazobenzene, were isolated by chromatography, identified by mass and NMR spectrometry, and synthesized by the reaction of aniline with phenylbutazone or its hydroxy analog, respectively.