Why does Lispro insulin have a faster onset of action than Regular insulin?
Onset of insulin action is defined as the time taken for insulin to reach 10% of its peak activity. Regular human insulin has a slower onset of action because, while in U-100 concentration, it has a strong affinity for self-association, which leads to the formation of hexamers. Absorption is delayed as the insulin dissociates from hexamers into dimers and finally monomers. Lispro is an insulin analogue formed by transposing the 2nd and 3rd to last amino acids in the -chain of insulin from proline/lysine to lysine/proline. With injection the dissociation into monomers occurs more quickly, giving a much faster onset of action.1 Reference: 1. Barnett AH, Owens DR. Insulin Analogues. The Lancet 1997;349:47-51.
