Aggregation of insulin and its prevention by carbohydrate excipients.

Aggregation of peptide/protein drugs is of concern as it may lead to reduced bioactivity, immunogenic reactions, blockage of infusion pumps or unacceptable physical appearance. Aggregation of insulin and its prevention by carbohydrate excipients was investigated in this study. Aggregation was induced in solid-state by incubating with moisture at 37 degrees C, or in solution by lyophilization, shaking or multiple passage through a needle. Moisture-induced aggregation in solid state with bovine and human insulin resulted in soluble aggregates which were analyzed by light scattering technique. They were found to be noncovalent by size exclusion chromatography. Three of the four carbohydrate excipients used, i.e., dextrose, Emdex and hydroxypropyl beta-cyclodextrin minimized the moisture-induced aggregation of bovine insulin, with dextrose and Emdex being somewhat more effective. In lyophilization studies, bovine insulin was found to aggregate more than human insulin. In syringe/needle study, aggregation increased as a function of the number of times the solution was passed through the needle. Aggregation induced by shaking insulin solutions resulted in insoluble aggregation, which could also be minimized by carbohydrate excipients.