The optimal goal for insulin therapy is to replicate physiological insulin levels normally found in the body, with rapid insulin action at meals and a slow decrease after meals.¹ With the advent of rapid-acting insulin analogs, the question becomes whether they are truly fast-acting or not. While they do appear to work faster than human insulin, a 2-hour time to maximum effect² does not seem “fast-acting” and perhaps reveals a marketing term as opposed to scientific validity.

Prandial insulin analogs have shown advantages in patient with type 1 diabetes when compared with regular human insulin. Results based on a Cochrane Database review demonstrated a clear advantage of prandial insulin analogs over regular human insulin in HbA_1c results.³ Unfortunately, these results were not duplicated in patients with type 2 diabetes.⁴ In a very small study (23 patients with type 2 diabetes patients and 10 controls), insulin aspart significantly reduced the area under the curve for postprandial hyperglycemia, preserved flow-mediated vasodilation, and improved endothelial function compared to regular insulin.⁵ Another study demonstrated a partial reversal of myocardial perfusion abnormalities with the use of an insulin analog through the improvement of glucose control, when compared to regular insulin.⁶ However, this was also a very small study (n = 20) and more information is needed before making any conclusions. When reviewing data for analog use in continuous glucose monitoring/insulin pumps, lispro demonstrated significant improvements in glycated hemoglobin over regular human insulin and was preferred by patients.⁷ All in all, prandial analogs appear to show advantages over regular human insulin as can be seen in Table 1.

Three rapid-acting insulins that are appearing are biochaperone lispro, ultra-rapid lispro (URLi), and faster aspart. Biochaperone lispro and URLi have faster “on” times than lispro, while faster aspart is quite similar in timing to insulin aspart.^8-10 All of these new formulations have also shown improvements in postprandial blood glucose levels in both patients with type 1 and type 2 diabetes.^11-13 When reviewing its clinical efficacy and application, fast-acting insulin aspart effectively improved HbA_1c values in patients with type 1 diabetes and demonstrated superior postprandial glucose over insulin aspart.¹⁴ Faster aspart was also non-inferior to insulin aspart for basal-bolus regimens as for HbA_1c levels, with no differences in hypoglycemia rates, body weight, and safety data.¹⁵ When used in insulin pumps, faster aspart had slightly higher results in HbA_1c but had more favorable results with interstitial glucose and postprandial glucose findings.¹⁶ Overall, the new rapid-acting insulins have modest advantages over prandial analogues which are summarized in Table 2.