Insulin delivery devices
Needle and syringe
A common way of administering insulin is with a needle and syringe. Syringes come in a range of capacities (1 mL, 0.5 mL or 0.3 mL) and with a range of needle types (different gauges — that is thicknesses — and lengths) attached. The needles have very fine points and special coatings to make injections relatively pain-free. Select a syringe that suits the size of the insulin dose you take and that has your preferred needle type and needle size attached.
One of the main advantages of the syringe system is the variety of products available. Needles and syringes also make it easy to use a mixture of different types of insulin ('mixed insulin').
However, some people find syringes daunting and not very convenient. For this reason a number of other delivery devices have been developed, including insulin pens, jet injectors and pumps.
Insulin pen injectors are a convenient and discreet way of administering insulin. They have a built-in dial that allows you to determine the amount of insulin to be injected, a short needle at one end, and a plunger at the other. Some are disposable, and don't need to be assembled before use, while others have a replaceable insulin cartridge that needs to be inserted (much like a fountain pen cartridge).
Insulin pens are particularly useful if you need to take premixed insulin. They have become popular for use by people with both type 1 and type 2 diabetes.
Insulin jet injectors
Jet injectors offer an alternative to needles, and work by sending a fine spray of insulin into the skin using a pressurised jet of air instead of a needle. However, jet injection isn’t any less painful than administering insulin with a needle, and may cause bruising or altered absorption levels. Jet injectors also require frequent cleaning and maintenance. They are not commonly used.
External insulin pumps
External insulin pumps are small devices the size of a pager that can be attached to your belt or placed in your pocket. They run off batteries. They are made up of an insulin reservoir connected to a tube, ending in a cannula or catheter, which is inserted under the skin of your abdomen. They can be set to deliver insulin at a slow, continuous rate throughout the day, or to release larger quantities at meal times or when blood sugar levels are high.
The main advantage of a pump is that it closely mimics the slow but continual release of insulin by the pancreas. However, you will still need to monitor your blood glucose levels regularly. Pumps have been useful in helping people with diabetes achieve tighter blood glucose control, but the risk of episodes of low blood sugar (hypoglycaemia) is higher. Another drawback of pumps is the risk of ketoacidosis if the catheter becomes blocked. Expense may also be an issue.
Implantable pumps which deliver insulin either intravenously or directly to the liver are currently being tested in people with diabetes (they are not yet available in Australia). They are usually implanted into the left side of the abdomen, and are designed to work in a similar way to external insulin pumps, that is, by giving a continuous ‘basal’ dose of insulin with the ability to deliver additional ‘bolus’ doses at meal times. Also under investigation is a version of the pump that measures blood glucose as well, and so delivers the correct insulin dose automatically. However, these devices are complicated and expensive, and can become blocked. If there are complications or infection at the implantation site the pump may have to be removed.
Insulin patches are also currently under development, but it is difficult for insulin to be absorbed through the skin. The patch is designed to release insulin slowly and continuously. Additional doses can be administered by pulling off a tab on the patch.
Insulin inhalers have been used to deliver pre-mealtime insulin. Insulin inhalers work like an asthma inhaler, but deliver dry powdered insulin into the bloodstream via the lungs. However, because the system can only be used to deliver fast-acting insulin, long-acting insulin must still be injected. Large doses are needed because only around 10 per cent of the dose actually reaches the bloodstream and that amount may vary, for instance, if you have a cold or asthma. Two types of inhalers were released commercially in the US, but have since been withdrawn from the market. Insulin inhalers are not currently available in Australia.
Other delivery devices
Insulin sprays, either for the nose or mouth, and oral insulin (insulin pills) are methods of insulin delivery that continue to be investigated. These options represent long-term possibilities for insulin delivery, as difficulties in obtaining adequate amounts of insulin in the bloodstream are yet to be overcome.
Islet cell transplantation
This is a recently developed surgical procedure — called the Edmonton protocol — whereby islet cells from a donated human pancreas are injected into the liver of a recipient with type 1 diabetes. The transplanted cells begin to secrete insulin, while the recipient needs to take immunosuppressive medications for life to prevent rejection of the transplanted tissue. Clinical trials continue to establish the safety and long-term effectiveness of this procedure as a means of supplying insulin, with encouraging early results.