Oxidation is one of the most common pathways of chemical degradation of active pharmaceutical ingredients and can significantly affect pharmaceutical product stability. This master's thesis aimed to evaluate the applicability of the Rancimat method as a rapid screening tool for assessing the oxidative stability of excipients during early formulation development. We investigated six polysorbate and four copovidone samples from different manufacturers and quality grades and their relationship with the oxidative stability of a model active pharmaceutical ingredient.
The Rancimat method was developed and optimized for both excipient groups and induction times were determined for all samples. Their effect on oxidation of the model active pharmaceutical ingredient was evaluated in a compatibility study using binary mixtures exposed to stress conditions. Three oxidation-related degradation products of the model active pharmaceutical ingredient were quantified by ultra high performance liquid chromatography, and the results of both approaches were compared by correlation analysis.
Induction times ranged from 0,89 h to 1,32 h for polysorbates and from 1,05 h to 3,90 h for copovidones. The longest induction times were observed for Polysorbate 80 NF, Multi-Compendial and Plasdone™ S-630 Ultra, respectively. Differences in degradation product formation were observed among the excipient samples. In both groups, shorter induction times generally tended to be associated with greater degradation product formation. No statistically significant correlation was confirmed within the individual excipient groups. However, when all samples were analyzed together, a statistically significant negative Spearman correlation was observed between induction time and both the total degradation product content and its increase relative to the initial sample at 60 °C and 30 % relative humidity.
The results indicate that the Rancimat method may be useful as a rapid screening tool for the comparative assessment of the oxidative stability of polysorbates and copovidones. Although it cannot replace compatibility studies, it may serve as a complementary tool during early pharmaceutical product development.
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