Insulin temperature and stability under simulated transit conditions

Purpose. The transit temperature profiles, mean kinetic temperatures (MKTs), and stability of insulin samples in both insulated and noninsulated containers exposed to summer and winter temperatures were evaluated. Methods. Regular insulin, isophane insulin human (NPH) insulin, and 70% isophane-30% regular (70/30) insulin were packaged in the most commonly dispensed quantity of four vials in noninsulated mailers and insulated containers with frozen gel packs. After packaging, sealed containers and mailers were placed in an environmental chamber for 24-120 hours and exposed to summer and winter transit conditions. Temperatures inside the environmental chamber were recorded every 15 minutes and maintained within 3 degrees C of the specified transit temperature. After exposure to the transit conditions, insulin cartons were removed from their packaging, visually inspected for changes in physical appearance, and stored at 4 degrees C until analysis. The MKT of each package was calculated. High-performance liquid chromatography was performed to determine sample stability, and size-exclusion chromatography was conducted to detect aggregate products of insulin. Results. Regardless of shipping conditions or packaging, all samples met the United States Pharmacopeia's (USP's) specified limits and retained product stability. Visual inspection of the physical appearance of insulin samples before and after temperature exposure revealed results similar to those described in the product inserts. Microscopic analysis of the injectable suspensions confirmed similar crystal morphologies before and after temperature exposure. Conclusion. Regular, NPH, and 70/30 insulin maintained potency within USP limits when stored in programmable environmental chambers simulating summer and winter overnight or three- to five-day ground delivery conditions, regardless of packaging material.