Insulin can be Stored outside Refrigerator without losing efficacy: Study

Patient with type 1 diabetes and some with type 2 diabetes require to inject themselves with several doses of insulin every day, which are suited to their diet and physical activity. The current pharmaceutical protocol recommends storing insulin vials between 2℃ and 8℃. However, in some regions of the planet like sub-Saharan Africa, not every household has a refrigerator. This forces people living with diabetes to go to the hospital, on a daily basis. Therefore, researchers of Médecins Sans Frontières (MSF) teamed up with the University of Geneva (UNIGE), Switzerland, to test the insulin storage in real conditions, that is at temperatures ranging from 25°C to 37°C for four weeks.

Researchers conducted the study in Dagahaley refugee camp, northern Kenya. They measured ambient temperature oscillated between 25℃ and 37℃ with a 12-hour cycle, exceeding usual recommendations for insulin use out of refrigeration. The UNIGE team used high-performance liquid chromatography to analyse the insulin. They assessed insulin heat stability under these specific temperatures, which were precisely reproduced, in the laboratory.

"As insulin vials can be used for four weeks after opening, we carried out our measurements over the same timeframe, first with vials kept at the temperatures found in Dagahaley, and then with 'control' vials that were refrigerated," explained Leonardo Scapozza, a professor of the School of Pharmaceutical Sciences in UNIGE's Faculty of Sciences in a press release.

Key findings of the study were:

• Upon analysis, researchers found that all the insulin preparations stored at fluctuating temperatures, as encountered in the field, recorded a potency loss of no more than 1%, just like those kept in cold storage during the required four weeks.

• They also observed that insulin activity was completely maintained. To verify this, they tested the action of insulin proteins on cells, compared with that of insulin, which had been intentionally deactivated.

• Upon monitoring the 3D-structure of the tested insulin by circular dichroism, they confirmed that insulin monomer conformation did not undergo significant modifications.

The authors concluded, "These results indicate that insulin can be stored at such oscillating ambient temperatures for the usual four–week period of use. This enables the barrier of cold storage during use to be removed, thereby opening up the perspective for easier management of diabetes in humanitarian contexts and resource-poor settings".

For further information:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245372