Effect of temperature on the potency & pharmacological action of insulin.

BACKGROUND & OBJECTIVE: Since proper storage of insulin is necessary for its action, the present study was undertaken to determine the extent to which improper temperature storage conditions could have contributed to the potency of the three insulin formulations tested. METHODS: Two human insulin formulations (regular and biphasic) from three different manufacturers were stored at 5 different temperatures. In vitro potency of insulin was determined by high performance liquid chromatography on every seventh day for a period of 28 days. For the in vivo study, insulin tolerance test was done by injecting human regular insulin intraperitoneally to rabbits on the 25(th) day of storage. Blood glucose was determined at 0, 15, 30 and 60 min after insulin injection using glucometer. RESULTS: Storage at 32 and 37 degrees C showed 14-18 per cent decrease in potency of insulin in both the formulations on 28(th) day for all the three brands. Also the rabbits receiving insulin stored in 32 and 37 degrees C did not show a significant decrease in blood sugar level when compared to those receiving insulin stored at 5 degrees C. INTERPRETATION & CONCLUSION: Improper storage of insulin decreases the potency and hence the pharmacological action of insulin. Patients should be educated on the proper methods of storage, and free supplies of insulin for more than two weeks use should not be dispensed.