McKenna's Pharmacology for Nursing, 2e

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P A R T 6  Drugs acting on the endocrine system

■■ BOX 38.5  Insulin delivery: Past, present and future

Past Subcutaneous insulin injection . The delivery of insulin by subcutaneous injection was introduced in the 1920s and changed the way that diabetic people were managed clinically, giving them a chance for a normal lifestyle. Research is ongoing to find more efficient and acceptable ways to deliver insulin to diabetic people. Present Subcutaneous insulin injection . This remains the primary delivery system. Insulin jet injector . This cylindrical device shoots a fine spray of insulin through the skin under very high pressure. Although it is appealing for people who do not like needles or have problems disposing of needles properly, it can be very expensive. Insulin pen . This syringe-like device looks like a pen. It has a small needle at the tip and a barrel that holds insulin (Figure 38.1). The person “dials” the amount of insulin to be given and injects the insulin subcutaneously by pressing on the top of the pen. This is advantageous for people who need insulin two or three times during the day but cannot easily transport syringes and needles. It is a subtle way to give insulin, and is popular with students and business people on the go. It is important to rotate the syringe 15 to 20 times before injecting the insulin to disperse it. People often forget this point after using the pens for a while, and as a result, may inject far too much or too little insulin when it is needed. Periodic reinforcement of the administration instructions is important. External insulin pump . This pump device can be worn on a belt or hidden in a pocket and is attached to a small tube inserted into the subcutaneous tissue of the abdomen. The device slowly leaks a base rate of insulin into the abdomen all day; the person can pump or inject booster doses throughout the day to correspond with meals and

activity. The device does have several disadvantages. For example, it is awkward, the tubing poses an increased risk of infection and requires frequent changing, and the person has to frequently check blood glucose levels throughout the day to monitor response. Long-acting insulin . The year 2001 brought the release of a subcutaneous insulin that lasts two to three times longer than NPH insulin. This should decrease the need for multiple injections and may increase glucose control, especially for people with erratic glucose levels during the night. Long-term effects of this type of insulin therapy are not yet known. Future Implantable insulin pump . This pump is surgically implanted into the abdomen and delivers base insulin as well as insulin boluses as needed directly into the abdomen to be absorbed by the liver, just as pancreatic insulin is (Figure 38.2). The disadvantages are risk of infection, mechanical problems with the pump and lack of long-term data on its effectiveness. This method is not yet available for general use. Insulin patch . The patch is placed on the skin and delivers a constant low dose of insulin. When the person eats a meal, tabs are pulled on the patch to release more insulin. The problem with this delivery method is that insulin does not readily pass through the skin, so there is tremendous variability in its effects. This route is not yet commercially available. Inhaled insulin . The lung tissue is one of the best sites for insulin absorption. An aerosol delivery system has been developed that delivers a powdered insulin formulation directly into the lung tissue. Research has been very promising, suggesting that this may be a more reliable method of delivering insulin in the future.

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FIGURE 38.1  Pre-filled insulin syringe. (From Farrell, M. & Dempsey, J. (2014). Smeltzer & Bare’s Textbook of Medical- Surgical Nursing (3rd edn). Sydney: Lippincott Williams & Wilkins.)

FIGURE 38.2  Person wearing an insulin pump. (From Dempsey, J., Hillege, S. & Hill, R. (2014). Fundamentals of Nursing and Midwifery (2nd edn). Sydney: Lippincott Williams & Wilkins.)