The degradation kinetics of the glycopeptide antibiotic dalbavancin in solution are systematically evaluated over the pH range 1-12 at 70°C. The decomposition rate of dalbavancin was measured as a function of pH, buffer composition, temperature, ionic strength, and drug concentration. A pH-rate profile was constructed using pseudo first-order kinetics at 70°C after correcting for buffer effects; the observed pH-rate profile could be fitted with standard pseudo first order rate laws. The degradation reactions of dalbavancin were found to be strongly dependent on pH and were catalyzed by protons or hydroxyl groups at extreme pH values. Dalbavancin shows maximum stability in the pH region 4-5. Based on the Arrhenius equation, dalbavancin solution at pH 4.5 is predicted to have a maximum stability of thirteen years under refrigerated conditions, eight months at room temperature and one month at 40°C. Mannosyl Aglycone (MAG), the major thermal and acid degradation product, and DB-R6, an additional acid degradation product, were formed in dalbavancin solutions at 70°C due to hydrolytic cleavage at the anomeric carbons of the sugars. Through deamination and hydrolytic cleavage of dalbavancin, a small amount of DB-Iso-DP2 (RRT-1.22) degradation product was also formed under thermal stress at 70°C. A greater amount of the base degradation product DB-R2 forms under basic conditions at 70°C due to epimerization of the alpha carbon of phenylglycine residue 3.
Keywords: Chemical stability; Cyclodextrin; Degradation products; Formulation; HPLC; Hydrolysis; Kinetics; Liquid chromatography-Mass spectrometry (LC/MS).
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