TYPES OF INSULIN

Different types of insulin are available today. The choice of dosage and insulin preparation depends on the needs of the client. The source of insulin (animal or human), brand and generic names, the dosage strength or concentration, and storage information are indicated on the label. Currently, the only insulins distributed in the United States and other countries are synthetic “human” insulins or their analogs. Insulin from a human source is designated on the label as recombinant DNA (rDNA origin).

Humalog insulin (lispro), a fast-acting insulin analog also known as recombinant DNA insulin, became available in 1996. Lispro acts within 5 to 15 minutes. Lispro can be administered 5 minutes before meals, whereas regular insulin can be administered 30 to 60 minutes before meals. Lispro is intended for subcutaneous administration only. Errors have occurred from the timing of lispro as well as its similarity to regular insulin; both are clear. Other rapid-acting insulin analogs followed lispro, such as aspart (NovoLog) and glulisine (Apidra) in 2004. Like lispro and regular, these analogs are clear.

The long-acting insulin Lantus (insulin glargine) was first approved by the Food and Drug Administration (FDA) in 2000. It is an analog of human insulin. Lantus permits once-daily dosing. It may be administered at any time during the day for 24-hour coverage without a peak; however, it must be administered at the same time every day. It is clear in appearance and intended for subcutaneous use only and cannot be mixed with other insulins. Lantus comes in distinctive packaging. The vial is tall and narrow, and the name Lantus is written in purple letters. The latest long-acting insulin analog, detemir (Levemir), is also generally given once daily. Detemir does not last as long as Lantus so clients may need a nighttime dose of the medication.

The only insulin on the market today is recombinant DNA insulin because it causes fewer reactions than insulin from animal sources. It is essential that the nurse knows where to locate this information. When an insulin order is written, the label will specify the origin of the insulin. Also found on the label is the type of insulin. This is indicated by a letter that follows the trade name. (Figure 20-1 shows information that can be found on an insulin label.)

The letters that follow the trade name on insulin labels (e.g., Humulin R, Humulin N) identify the type of insulin by action and time (see Figure 20-1). Nurses must be familiar with the onset, peak, and duration of action, which vary depending on the type of insulin. There are three basic action types of insulins: rapid acting (regular, lispro [Humalog], aspart [NovoLog], glulisine [Apidra]); intermediate acting (NPH); and long acting (glargine [Lantus], detemir [Levemir]). The expiration date and concentration are also indicated on the label and are important to check. Notice the uppercase letters on all insulin labels, for example, N for NPH as in Figure 20-1. You will see R for regular insulin. Regular and NPH are the two types of insulin used most often.

Look at the Humulin insulin label in Figure 20-1. Notice that the label shows Humulin (trade name), followed by the letter N. N = NPH (intermediate acting). These letters are important identifiers for insulin.

Types of U-100 Insulins

Nurses must be familiar with the three types of U-100 insulins. Below are samples of labels according to their action times.

FAST ACTING (RAPID ACTING)

INTERMEDIATE ACTING

LONG ACTING

Practice Problems

Using the labels below, identify the insulin trade name and action time (rapid acting, intermediate acting, or long acting).

1. Trade name ________________ Action time ________________

    

2. Trade name ________________ Action time ________________

3. Trade name ________________ Action time ________________

4. Trade name________________ Action time ________________

    Answers on p. 650 ________________________________

APPEARANCE OF INSULIN

Regular insulin, Humalog (lispro), and Lantus (insulin glargine), Apidra (insulin glulisine), aspart (Novolog), and Levemir (insulin detemir) insulin are clear. All other insulin is cloudy. They include NPH and fixed combination insulins such as Humulin 70/30, 50/50, and Humalog 75/25.

FIXED-COMBINATION INSULINS

Fixed-combination insulins are now available (Figure 20-2). These insulins have become popular for clients who must mix fast-acting and intermediate-acting insulins. The purpose of the fixed-combination insulins is to simulate the varying levels of insulin within the bodies of diabetic persons. The availability of the premixed combination insulins has also decreased the need for clients to mix insulins. Examples of fixed-combination insulins are Humulin 70/30, Novolin 70/30, Humulin 50/50, and Humalog Mix 75/25. Humulin 70/30 is used most often.

To understand fixed-combination insulin orders, it is important for the nurse to understand that, for example, 70/30 concentration means there is 70% NPH insulin (isophane) and 30% regular insulin in each unit. Therefore if the order was 30 units of Humulin 70/30 insulin, the client would receive 21 units of NPH (70% or 0.7 × 30 units = 21 units) and 9 units of regular insulin (30% or 0.3 × 30 units = 9 units).

The 50/50 insulin concentration means there is 50% NPH insulin and 50% regular insulin in each unit. Therefore if the order was 20 units of 50/50 insulin, the client would receive 10 units of NPH (50% or 0.5 × 20 units = 10 units) and 10 units of regular insulin (50% or 0.5 × 20 units = 10 units). It is important to note that Humalog Mix 75/25 contains 75% lispro protamine insulin and 25% lispro “rapid insulin.” Figure 20-2 shows labels of fixed-combination insulins.

INSULIN ADMINISTRATION

Insulin is available in 100 units per mL multidose vials and supplied in units that denote strength. The major route of administration for insulin is by subcutaneous injection; it is never administered intramuscularly. Regular insulin, aspart, and glulisine are approved insulins for intravenous administration. Dosage and frequency of insulin administration are highly individualized. It can also be administered with insulin pens that contain a cartridge filled with insulin or with a CSII pump (continuous subcutaneous [subcut] insulin infusion). The CSII pump is used to administer a programmed dose of a rapid-acting 100 units per mL–insulin at a set rate of units per hour. Figure 20-3 shows the various delivery systems used to administer insulin.

Measuring Insulin in a U-100 Syringe

Insulin is always ordered in units, the medication is supplied in 100 units per mL, and the syringes are calibrated for 100 units per mL and marked U-100. Therefore no calculations are required to prepare insulin dosages subcutaneously. We will focus on the administration of insulin with the U-100 syringes, of which there are different types.

1. Lo-Dose syringe—It has a capacity of 50 units (0.5 mL). Each calibration on the syringe measures 1 unit. There is also a 30-unit (0.3 mL) syringe, which is used to accurately measure very small amounts of insulin. It is marked in units up to 30 units. Each calibration is 1 unit.

2. 1-mL (100-unit) capacity syringe—The 100-unit syringe comes with even and odd numbers on it. There are two types of 1-mL syringes in current use.

a. The single-scale syringe is calibrated in 2-unit increments. Any dosage measured in an odd number of units is measured between the even calibrations. This would not be the desired syringe for clients with vision problems.

b. The double-scale syringe has odd-numbered units on the left and even-numbered units on the right. To avoid confusion, the scale on the left should be used for odd numbers of units (e.g., 13 units) and the scale on the right, for even numbers of units (e.g., 26 units). When even numbers of units are measured, each calibration is then measured as 2 units.

CAUTION

Administer insulin in an insulin syringe used only for the administration of U-100 insulin. Do not use an insulin syringe to measure other medications that are measured in units. Syringes of 30 and 50 units measure a smaller volume of insulin but are intended for the measurement of U-100 insulin only. Use the smallest capacity insulin syringe available to ensure the accuracy of dosage preparation.

To review what the syringes look like, see Figure 20-4 for the four types of insulin syringes discussed.

Lo-Dose Syringe

Let’s look at some insulin dosages measured in the syringes to help you visualize the amounts in a syringe. Syringe A shows 30 units and syringe B shows 37 units in a Lo-Dose syringe.

Practice Problems

Using the syringes below, indicate the dosages shown by the arrows.

5. ________________

6. ________________

    Using the syringes below, shade in the dosages indicated.

7. 17 units

8. 47 units

    Answers on p. 650 __________________________________

Single-Scale 1-mL Syringe

Now let’s look at what dosages would look like on a single-scale 1-mL syringe. The syringes below show 25 units in syringe A and 55 units in syringe B. Notice that the dosages are drawn up between the even calibrations.

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