Quality of In-Use Insulin Under Real-World Storage Conditions in Mwanza, Tanzania

Stability of insulin varies on storage conditions, handling, and types of formulations, and in Tanzania, unreliable refrigeration and climate fluctuations can compromise storage, which can reduce potency. Real-world data are crucial for optimizing diabetes management in developing countries. Previous studies have reported mixed findings, linking insulin degradation to temperature fluctuations, formulation issues, and distribution challenges. This study assessed the impact of storage conditions on insulin content during usage among diabetic patients at Bugando Medical Centre (BMC).

This cross-sectional study, conducted from April to July 2024 in Mwanza, assessed the quality of 16 batches of insulin using the high-performance liquid chromatograph (HPLC) method. Insulin samples were collected from 48 diabetic patients attending the diabetic clinic at BMC and analyzed for physical appearance, identity, and concentration, while storage conditions were monitored using a Bluetooth temperature data logger.

Of the 16 insulin batches analyzed, 7 (43.8%) had low active insulin content, while 4 batches (25%) contained no active insulin at all. Among the 48 patients sampled, 24 (50%) were using substandard insulin. Of the 26 patients who used 2 separate vials, 15 had at least 1 vial that failed to meet standard specifications. Among the 20 patients using a single combined vial, 7 (35%) had low insulin content.

All patients stored insulin within recommended temperature conditions; however, several samples were substandard, with some batches failing specifications. While 56.2% met United States Pharmacopeia (USP) requirements, the remaining showed variability and reduced concentrations.