Insulin pen devices

These devices have an insulin cartridge instead of ink and a double-ended needle instead of a nib. This pierces the bung of the insulin cartridge ready for use. The insulin dose is dialled up or clicked in at the other end of the pen. A plunger pushes the bottom of the cartridge down, ejecting the chosen dose of insulin through the needle.

Each device has a slightly different action. The pen does the same job as a syringe and needle but there is no need to draw up the insulin dose from a bottle. This improves accuracy although with the models in which the patient has to depress the plunger repeatedly to administer the insulin it is possible to lose count. Insulin pens are also much more portable than a full syringe and needle and can be carried in a pocket or bag without the insulin in the cartridge 'going off'.

Choose the best pen for each user. Different pens have different features including: the way in which the insulin dose is selected, whether this is counted or dialled up, the ease of operation, delivery of the dose (either by a twisting motion or depressing a plunger), knowing whether the insulin has gone in, knowing how much insulin is left, and when to change the cartridge. Most devices are quite robust. There are chunky pens which are easy to grip, those with concealed needles, and one which delivers 0.5 units of insulin charges. It is essential to teach the patient how to prime the pen, load an insulin cartridge, and how to expel air from the needle before each injection. Patients are usually advised to hold the pen vertically, needle up, and waste a few units of insulin before each injection to clear the needle of air. If there is air in the needle or cartridge this may

Casing

Novorapid Piston
Body

-Piston rod

Dose indicator window

|_J--Batch number

Needle

Rubber membrane

Cartridge ■ Rubber piston

Dosage selector -Push button

Fig. 9.1 Insulin pen remain undetected and cause dosage errors. The patient must always read the instructions and practise with a diabetes specialist nurse or other person trained in pen use.

There is now a range of pre-loaded disposable insulin pens. Virtually all the patient has to do is screw on a pen-needle, dial up the dose, and inject the insulin. Loading errors are abolished as the insulin is already in the pen. These pens can be used for patients of all ages, including some elderly people or their families who might otherwise need supervision by the district nurse. These pens cannot deliver a dose smaller than two units which may be difficult for patients on small doses. Pre-loaded, disposable pens currently available on prescription include Actrapid, Insulatard, Mixtard (10, 20, 30, 40, 50), and Novorapid (Novo Nordisk) and the Lilly Humaject range.

Single units of insulin can be given with the Autopen, BD pen Ultra, Humapen, Innovo, and Novopen 3 devices. Half units can be injected with Novopen 3 Demi. Magnifiers are available for people with poor vision. Insulins available for pen injection are updated from time to time (check the Monthly Index of Medical Specialities—MIMS). They include Actrapid, Humalog, Humulin S, Hypurin Bovine or Porcine Neutral, Insuman Rapid, Novorapid; Humulin I, Hypurin Bovine or Porcine Insulatard, Insulatard; Humalog Mix25, Humulin M2, Insuman Comb (15, 25), Mixtard (10, 20, 30, 40, 50).

All patients on insulin should be considered for insulin pen therapy—it is usually more accurate, convenient, comfortable, and practical. But it is the patient who must choose the method he or she prefers.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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