Stability of U-10 and U-50 Dilutions of Insulin Lispro

Abstract

Background: Insulin lispro, a rapid acting analog of human insulin, has been shown to be useful in the treatment of children with diabetes. However, lower concentrations of this insulin may be needed to facilitate optimal clinical use. Therefore, the stability of insulin lispro when diluted with an appropriate diluent was evaluated. Methods: Insulin lispro (U-100, 100 U/mL) was diluted with sterile Neutral Protamine Hagedorn (NPH) diluent to U-10 and U-50. After storage for 7, 14, 21, 28, and 32 days at 5°C and 30°C, the diluted insulins were analyzed by high-performance liquid chromatography(HPLC) to determine potency, purity, polymer, and preservative (metacresol or phenol) content in addition to physical appearance and pH determinations. Microbiological testing for preservative effectiveness was performed on the U-10 and U-50 solutions after 32 days at both temperatures. Results: U-10 and U-50 dilutions of insulin lispro stored at 5°C and 30°C maintained potency and purity throughout the 32-day testing period. Additionally, both control and diluted vials maintained antimicrobial effectiveness. Conclusion: Insulin lispro when diluted with the appropriate diluent demonstrates acceptable stability when stored at 5°C and 30°C for a period of 32 days.