Nucleophilic Addition in Aqueous Apomorphine Formulation Solutions in the Presence of Sodium Metabisulfite: Implications for Formulation Development and Manufacturing.

The purpose of this study was to investigate a potential nucleophilic addition mechanism in aqueous apomorphine formulation solutions in the presence of widely used antioxidants such as sodium metabisulfite (Na2 S2 O5 ). The findings of this investigation provide insights into how sodium metabisulfite can influence the formation of particulate under the conditions leading to the auto-oxidation of apomorphine to apomorphine orthoquinone. The addition products resulting from the reaction of bisulfite nucleophile on apomorphine orthoquinone in a Michael addition fashion were identified and characterized using ultraviolet-visible spectroscopy and mass spectrometry.