Background and Importance Insulins remain essential for people living with diabetes worldwide. As a biological product, it is susceptible to heat, light and sheer conditions. Little is known about actual household storage temperature of insulins, especially in the setting where room temperature is far beyond 25°C, under which insulin stability might be compromised.

Aim and Objectives To determine home storage temperature of in-use human insulins among ambulatory type 2 diabetes (T2D) people and to subsequently test insulin stability under the simulated maximum storage temperature identified.

Material and Methods People with T2D who collected prescribed insulins from a hospital dispensary and received a self-assembly pen with either regular insulin (RI), isophane (NPH) or premixed RI/NPH insulins, were given a temperature logger to track their home storage temperature of insulins for 5–7 days (N=47). The maximum out of the recommended range temperature identified was simulated in laboratory where the insulins were kept for 4 weeks. The percentages label amount of the insulins imitated daily use were then analysed at a weekly interval, following the 42^nd ed. United State Pharmacopoeia. The acceptable range was 95 -105% with reference to standard. Descriptive statistics were used to present the recorded temperature.

Results Majority (81%) of the patients keeping insulin in a refrigerator had temperature outside the 2 to 8°C range. Room temperature storage was totally above 30°C (maximum 43.6 °C). At the simulated isothermal 42±2°C, RI, NPH and premixed RI/NPH insulins had percentage label amounts in the acceptable range at 2, 3 and 4 weeks, respectively.

Conclusion and Relevance Actual home storage temperatures of the insulins were out of the appropriate ranges. These were similar to Braune at al.¹ Under the simulated 42±2°C, in-use human insulins retained acceptable content, with regular insulin being stable up to week 2; NPH and the premixed insulin up to week 3 and week 4, respectively. The results were in line with the Kenya study² but they set the maximum temperature at 37^°C. Pharmacists should be aware of true household storage temperature of insulin products and take into account the number of days it takes for one insulin cartridge to be finished against with the probable stability duration.

References and/or Acknowledgements 1. https://doi.org/10.1089/dia.2019.0046

2. https://doi.org/10.1371/journal.pone.0245372

Conflict of Interest No conflict of interest.