Insulin is usually classified according to onset, peak effect and duration of action. The currently available insulins include rapid-acting, lispro (Humalog® Eli Lilly and Company); short-acting, regular; intermediate-acting, NPH and Lente® (Eli Lilly and Company), and long-acting, Ultralente® (Eli Lilly and Company).
Regular human insulin and lispro insulin are the only clear insulin solutions. All other types of insulin are cloudy suspensions. They are also the only two insulins that can be given intravenously. When given intravenously regular human insulin and lispro insulin have the same onset, peak and duration of action.
Lispro is an insulin analog that is identical to human insulin except for a modest change in its molecular structure. Insulin is a hormone consisting of two polypeptide chains of amino acids, an A and a B chain. In the production of the insulin analog from the regular insulin molecule the position of the amino acids lysine and proline are reversed on the B chain.
This molecular change produces the insulin analog, lispro, with a faster rate of absorption and shorter duration of action than regular human insulin.
Many individuals with both Type 1 and 2 diabetes use insulin pumps, also known as continuous subcutaneous insulin infusion (CSII) devices, to maintain tight control of their blood sugars.
Currently, a certain type of regular insulin called Velosulin® Human BR (Novo Nordisk Pharmaceuticals Inc.) is used in insulin pumps to deliver this continuous infusion of insulin subcutaneously.
The chemical and pharmacologic properties of lispro insulin suggest that it would be an even more effective choice for insulin pump use.
Many individuals with diabetes are already currently using it with their pumps and have achieved better control with less hypoglycemia while using it. More clinical trials have to be completed before FDA approval for product labeling can be obtained.
Lispro vs. Regular Insulin
In order to most effectively understand the clinical impact and importance of the insulin analog we need to compare the onset, peak and therapeutic duration of action between lispro and regular human insulin.
The onset of action for lispro is 15-30 minutes compared to 30-60 minutes for regular human insulin. The peak effect of lispro is within 1-2 hours compared to 2-4 hours for regular human insulin.
The therapeutic or effective duration of action is defined as the amount of insulin needed to keep blood glucose levels in normal limits. The therapeutic duration of action for lispro is 3-4 hours compared to 6-8 hours for regular human insulin.
The clinical indications of lispro are numerous. They include:
* A dose of lispro insulin peaks in one half the time and double the concentration of a comparable subcutaneous injection of human regular insulin.
* Lispro insulin can generally be used in place of human regular insulin to provide better coverage of postprandial glucose elevations.
* Lispro insulin can be injected immediately prior to eating (usually less than 15 minutes before the meal). Injecting lispro 30-60 minutes before the meal can result in hypoglycemia.
* Lispro insulin is designed to cover mealtime insulin needs (bolus dose). Health care providers may also include longer acting insulins (NPH, Lente, Ultralente) to cover insulin needs between meals and overnight (basal/background dose).
Facts Regarding Storage of Lispro
Keep lispro insulin in the refrigerator. After a bottle is opened you can keep it at room temperature for up to 28 days. Do not freeze or expose it to temperatures above 86 degrees Fahrenheit. Keep it away from direct heat and light. Lispro insulin cartridges for use in insulin pen injecting devices may be kept unrefrigerated for 28 days.
Lispro insulin may be mixed with NPH, Lente or Ultralente. Any mixture should be given 15 minutes before the meal and immediately after mixing.
The most common side effect is hypoglycemia, which can occur secondary to incorrect dosing or injecting lispro later than within 15 minutes of eating. Other rare reactions include depression in the skin at injection site or thickening of the skin at injection site.
Nursing Implications/Patient Education
Lispro insulin enables individuals with diabetes to adapt quickly to changing schedules and activities. Changes in individual schedules or mealtimes secondary to hospitalization or outpatient testing can be adapted more effectively with the use of lispro. People using lispro can dose and eat!
Some cautions regarding lispro include:
* Individuals with diabetes should be advised to be prepared to eat a meal or snack before they self inject with lispro.
* Because of lispro's unique action times it is useful in managing diabetes during an acute illness in the home. Supplementing an individual's usual daily dose of insulin with lispro according to blood sugar and urine ketone readings allows for a more physiologic treatment of the individual with diabetes during illness, without the risk of hypoglycemia from overlapping doses of regular human insulin.
* Because of its shorter duration of action especially after the evening meal there is decreased risk of nocturnal hypoglycemia, a serious problem in institutional and home settings.
* Lispro insulin is available by prescription only.
Lispro insulin has been available in the United States since July, 1996. Diabetes research and clinical trials during the past decade have indicated that intensive therapy (insulin pump therapy or 4-5 injections insulin per day) will reduce the risk and severity of microvascular complications in the individual with diabetes.
The increased use of lispro in insulin pump therapy or its use in treating postprandial glucose rises with premeal injections, requires that every licensed nurse caring for individuals with diabetes possess a keen understanding and appreciation of the role of lispro in diabetes management. *
1. Howet, D.C., et al. (1994). [Lys(B28), Pro(B29)]- human insulin, a rapidly absorbed analogue of human insulin. Diabetes, 43: 396-402.
2. White, J., Campbell, K., Yarborough, P. (1998). Pharmacologic therapies. In A core curriculum for diabetes education. Chicago: AADE, pp. 297-306.
Kathleen McDonald is the nurse practitioner, Diabetes Services at Robert Wood Johnson University Hospital, New Brunswick, NJ. She has lectured extensively on the state and national level on diabetes education and management.