What is rapid-acting insulin?

Updated: Oct 04, 2017
  • Author: Mini A Mathew, DO, PharmD; Chief Editor: George T Griffing, MD  more...
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Rapid-acting insulins with a short duration of action include insulin aspart (NovoLog), insulin lispro (Humalog), and insulin glulisine (Apidra). Their onset of action is approximately 5-15 minutes, peak action is between 30 and 90 minutes, and duration of action is approximately 4-6 hours. Regular insulin (Humulin R, Novolin R) is categorized as short-acting with a short duration of action and regular onset of action. Regular insulin's onset is 30-60 minutes, peak is 2-3 hours, and duration of action is approximately 8-10 hours. In general, insulin lispro, insulin aspart, and insulin glulisine are slightly more effective than regular insulin in decreasing HgbA1C, with lessnocturnal hypoglycemia. [5]

In September 2017, Fiasp (insulin aspart injection) was FDA-approved to improve glycemic control in adults with type 1 (T1D) and type 2 diabetes (T2D). This rapid-acting human insulin analog can be dosed at the start of a meal or within 20 minutes after starting a meal. Fiasp is formulated with niacinamide which helps increase the speed of the initial insulin absorption. A pharmacokinetics study of adult patients with type 1 diabetes showed that Fiasp appeared in the circulation in approximately 2.5 minutes after administration. The time to maximum insulin concentrations was achieved in roughly 63 minutes after administration. [6]

In the manufacturing of regular insulin, zinc atoms are added, causing the formation of hexamers. [1] Because they are larger molecules, they diffuse slowly into the circulation. On the other hand, insulin lispro has lysine and proline inverted at the B28 and B29 position and insulin aspart has the proline at position 28 replaced by aspartic acid. [1] These changes in structure reduces the formation of dimers and hexamers, and they are rapidly absorbed. The short-acting insulins typically are used as bolus insulin given premeal. The rapid-acting insulins are administered immediately before a meal, whereas regular insulin is administered 30 minutes before a meal. [7]

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