Exploration of Temperature and Shelf-Life Dependency of the Therapeutically Available Insulin Detemir.

Purpose: Insulin, in typical use, undergoes multiple changes in temperature; from refrigerator, to room temperature, to body temperature. Although long-term storage temperature has been well-studied, the short term changes to insulin are yet to be determined. Insulin detemir (IDet) is a clinically available, slow-acting, synthetic analogue characterised by the conjugation of a C14 fatty acid. The function of this modification is to cause the insulin to form multi-hexameric species, thus retarding the pharmacokinetic rate of action. In this investigation, the temperature dependence properties of this synthetic analogue is probed, as well as expiration. Methods: Dynamic light scattering (DLS) and viscometry were employed to assess the effect of temperature upon IDet. Mass spectrometry was also used to probe the impact of shelf-life and the presence of certain excipients. Results: IDet was compared with eight other insulins, including human recombinant, three fast-acting analogues and two other slow-acting analogues. Of all nine insulins, IDet was the only analogue to show temperature dependent behaviour, between 20 degrees C and 37 degrees C, when probed with non-invasive backscatter dynamic light scattering. Upon further investigation, IDet observed significant changes in size related to temperature, direction of temperature (heated/cooled) and expiration with cross-correlation observed amongst all 4 parameters. Conclusions: These findings are critical to our understanding of the behaviour of this particular clinically relevant drug, as it will allow the development of future generations of peptide-based therapies with greater clinical efficacy.