Comparison of the Levels of Rubber Stopper-Related Organic Leachables in Commercially Available Vialed Liquid and Lyophilized Drug Products

Purpose Rubber stoppers that seal the primary packaging systems of parenteral pharmaceutical products have the potential to introduce impurities into the drug during storage. While this interaction has been well characterized for products stored as an aqueous liquid, it is not well understood how the interaction is affected when the product is stored as a lyophilized solid. Accordingly, the goal of this study was to determine how lyophilization affects the propensity for impurity migration (leaching) into the product. Methods The concentration of substances in the stopper and the concentration of these substances that had leached into the product at equilibrium were measured and used to calculate equilibrium constants, which quantifies the degree of partitioning of each compound between each unique stopper and drug matrix, for twelve lyophilized and twelve liquid commercial drug products. Results Lyophilized products were shown to have a significantly increased propensity to contain substances that migrated from their stopper as compared to liquid products, as supported both by the general qualitative/quantitative leachable profile and the equilibrium constants obtained. Conclusions The conversion of a liquid drug formulation to a lyophilized solid during storage will increase the number and concentration of impurities leached from the stopper.