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Insulin-delivery devices

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Debbie Hicks, BA, DN Cert, PWT Cert, RN, Senior Diabetes Specialist Nurse.

The Michael White Centre for Diabetes and Endocrinology, Hull Royal Infirmary, Hull

Diabetes affects 2-3% of the population of the UK, which equates to over 1.4 million people (Leedham, 2000). This number is expected to rise to over three million by the year 2010 due to poor lifestyles and an increasingly ageing population (Diabetes UK, 2001).

Diabetes affects 2-3% of the population of the UK, which equates to over 1.4 million people (Leedham, 2000). This number is expected to rise to over three million by the year 2010 due to poor lifestyles and an increasingly ageing population (Diabetes UK, 2001).

Types of diabetes mellitus
There are two main types of diabetes mellitus. Type 1 diabetes occurs commonly in children and young adults and accounts for approximately a quarter of the total population with diabetes. There is a total lack of endogenous insulin produced by the beta cells of the pancreas; therefore insulin therapy is the only effective treatment available. This is administered via a subcutaneous injection.

In Type 2 diabetes there is beta cell dysfunction and insulin resistance. This means that there is some endogenous insulin produced; however, due to the insulin resistance linked to the obesity in patients with Type 2, the insulin is less effective at lowering abnormal blood glucose levels.

Diet should always be the first line of treatment for people with Type 2 diabetes but, due to the disease progression, people with this condition usually move to hypoglycaemic agents relatively quickly after diagnosis. Oral medications such as the sulphonyureas or biguanide have commonly been used to treat Type 2 diabetes. However, following the UK Prospective Diabetes Study (UKPDS, 1998) people with Type 2 diabetes are now more likely to be treated with insulin if unable to achieve satisfactory glycaemic control with oral hypoglycaemic agents.

Insulin-delivery devices
The most basic of insulin-delivery devices is the disposable needle and syringe.

Pen devices - In 1984, Novo Nordisk launched the first pen device, which revolutionised injections for people with diabetes taking insulin. Other pen device manufacturers include Lilly, Aventis, Owen Mumford and Medical House Products Ltd. The most immediate benefit provided by the pen was portability. The pen device was able to be carried easily in a pocket or handbag and had a small insulin cartridge able to deliver accurate multiple doses, but did not need to be kept in a refrigerator. The pen device was discreet in appearance; therefore an insulin injection could be given without attracting unwanted attention.

Since the mid-1980s the pen devices have become more sophisticated with specific features such as audible clicks to alert someone with visual problems to the dose of insulin being dialled, allowing them continued independence. They have been designed in an ergonomic fashion with different textures to fit better into the hand and ensure ease of use. Larger cartridges have been made to reduce the number of changes required and disposable pens have been produced for those people who have difficulty changing the cartridges.

Further innovations - In 1998 the Innovo insulin doser was launched. This injection device added further benefits to the existing pen devices in that it had a unique digital display and memory function. The memory function dealt with the all-too-common event of anxiety over a missed injection. The act of the daily insulin injections becomes so routine that a person requiring insulin injections often administers the injection without thinking about it unduly. The Innovo doser memory function gives a display of how much insulin was given at the previous injection and how long ago the last injection was given. The Innovo doser is short and compact, much like a pager, and is designed to be easy for small hands to manipulate.

September 2001 saw the launch of the InnoLet (Novo Nordisk) insulin-delivery device. This disposable device has a simple dialling mechanism. It offers major benefits for people with visual problems due to its large, easy-to-read numbers and audible clicks as the dose is dialled up. The InnoLet is also easy to manage for those with dexterity problems.

In 2002 the Optiset (Aventis) and Flexpen (Novo Nordisk) devices were launched. These pen devices are disposable and are ideal for those patients who find using a reusable pen difficult due to the cartridge changes. The Optiset pen has an added feature in that the dose can be pre-set to deliver a fixed amount. This is a benefit for some older patients who find dialling doses difficult but who wish to remain independent.

Also launched in 2002 was the new needle-free injection device - MHI-500 (Medical House Products Ltd). This device forces insulin through the skin under pressure.

Storing insulin devices
Insulin is most effective when stored at an ambient temperature. Patients using injection devices are advised to keep them at room temperature and avoid extremes of temperature. Insulin that is in use is safe for up to 28 days when kept at room temperature (refer to manufacturer's instructions); however, unopened insulin that is being stored should be kept in a refrigerator at 2-88C. It should not be used after the expiry date (Becton Dickinson, 2001).

Selecting a delivery device
It is important that the person requiring insulin injections has the chance to see and handle the range of insulin devices so they are able to make a choice as to what device they use to inject. People who are more physically and psychologically comfortable with their insulin-delivery device have an improved overall attitude to insulin therapy (Graff and McClanahan, 1998). The selected device should be supplied with a second device as back up and with careful instruction supported by written information.

Insulin pumps
In recent years insulin pumps have gained popularity. Insulin pumps are specifically targeted for those patients who are highly motivated to control their diabetes and who are willing to perform multiple blood glucose tests every day. As yet insulin pumps and the necessary equipment are not available on the NHS. The National Institute for Clinical Excellence is currently evaluating the benefits of pumps.

Inhaled insulin
Current research is evaluating the effectiveness of inhaled insulin, which would be a major advance in treatment because it would negate the need for injections.

Conclusion
Since insulin became available improved technology in the form of insulin devices has made the injection procedure easier and less painful for patients. Normal activities such as eating out have become more accessible and less problematic. Pen devices and the new injection devices have reduced the stigma attached to injecting.

It is very important that the person requiring insulin injections is fully involved in both the treatment decision and device choice. Involvement in the process will ensure that the person is fully committed to the insulin therapy, as they will depend on these injections to maintain their health in future.

PSYCHOLOGICAL IMPACT OF DIABETES
The person with diabetes needs to adhere to a healthy diet, take medications numerous times during the day in association with blood glucose tests and take part in exercise just to maintain their blood glucose at a near-normal level. This may sound easy, but it is not when you have to do it for the rest of your life and be aware that if you do not achieve near-normal blood glucose levels you are at risk from all the associated complications such as nephropathy, retinopathy, neuropathy and an increased risk of myocardial infarction or stroke (Department of Health, 2001).

Education and support are crucial to good self-care and should be available to anyone who is newly diagnosed as well as on an ongoing basis following diagnosis. People with diabetes should be empowered by health-care professionals to take control of their condition, but they can only do this with appropriate knowledge.

INJECTION PROCEDURE
Insulin is administered as a subcutaneous injection. As the thickness of the subcutaneous tissue varies between individuals and from one body region to another, it is crucial that the correct length of needle and appropriate injection technique are used and to ensure that the insulin is delivered into the subcutaneous layer and not into muscle (Becton Dickinson, 2001). The needle should be inserted into the skin at a vertical 90 degree angle with a lifted skinfold (Becton Dickinson, 2001).

The needles used, for both syringes and injection devices, are available in different lengths: 5mm (pen needles only), 8mm and 12.7mm. The 5mm needles are appropriate for thin people and can be used without a lifted skinfold. The 8mm needles are appropriate for most adults, whereas the 12.7mm needles are more suited to obese people.

Advice is always given regarding appropriate injection sites and site rotation (Figure 1). This ensures that the insulin is absorbed correctly and prevents overuse of one site, causing lipohypertrophy (Becton Dickinson, 2001).

The first injection should always be administered by the patient but supported and observed by the diabetes specialist nurse. It is crucial that those who are able to self-administer do so to conquer any fears associated with the injection procedure.

INSULIN REGIMENS
The choice of insulin regimen should be a joint decision between the patient and the health-care professional, taking into consideration the patient's lifestyle and preference. If the regimen is too complicated or arduous the person is less likely to adhere to it (Graff and McClanahan, 1998). There are three main insulin regimens:

- Basal-bolus: this regimen involves an injection of fast-acting insulin given before each meal and an injection of intermediate insulin or long-acting analogue given at bedtime. The main benefit of this regimen is flexibility as it allows the patient to choose when and how much he or she wishes to eat

- Twice daily: this regimen requires only two injections per day given usually at breakfast and the evening meal. The insulin used for this regimen is normally pre-mixed insulin or intermediate insulin

- Once daily: this regimen was used with intermediate insulin normally for frail elderly people where symptom control was the goal rather than tight glycaemic control. However, since the launch of the long-acting analogue insulin glargine, this regimen will become more popular.

Once the appropriate insulin regimen has been chosen the next stage is the choice of insulin delivery device.

Becton Dickinson. (2001) Getting Started with Insulin. Oxford: Becton Dickinson UK Ltd.

Diabetes UK. (2001)Diabetes: The figures (Fact sheet number 2). Available at www.diabetes.org.uk

Department of Health. (2001)Diabetes National Service Framework: The impact of diabetes. London: The Stationery Office. Available at www.doh.gov.uk/nsf/diabetes/impact.htm

Graff, M.R., McClanahan, M.A. (1998)Assessment by patients with diabetes mellitus of two insulin delivery systems versus vial and syringe. Clinical Therapeutics 20: 3, 486-496.

Leedham, I. (2000)Diabetes Health Promotion in Ethnic Minority Communities: Report to the British Diabetic Association (Wales). London: Diabetes UK. Available at www.diabetes.org.uk

UK Prospective Diabetes Study Group. (1998)Intensive blood glucose control with sulphonyureas compared with conventional treatment and risk of complications in patients with Type 2 diabetes (UKPDS 33). Lancet 352: 837-853.

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