Commercially Available Insulin Products Demonstrate Stability Throughout the Cold Supply Chain Across the United States
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A recent publication questioned the integrity of insulin purchased from U.S. retail pharmacies. We sought to independently validate the method employed, isotope dilution solid phase extraction (SPE) liquid chromatography (LC) mass spectrometry (MS) and expand analysis to two U.S. Pharmacopiea (USP) methods (high performance LC with ultra-violet detection (LC-UV) and LC-MS).
Research Design and Methods
Each method was used to evaluate nine insulin formulations, purchased at four pharmacies, within five geographic locations in the U.S.
All human and analogue insulins measured by the USP methods (n=174) contained the expected quantity of active insulin (100±5 U/mL). When using isotope dilution SPE-LC-MS, U/mL values were well below product labeling due to unequal recovery of the internal standard compared to target insulin.
Insulin purchased from U.S. pharmacies is consistent with product labeling.