What's new in diabetes care
Introduction to diabetes
Types of diabetes
Diagnosis
Risk factors & screening

Insulin therapy

• Groups of insulin
• Insulin injection sites
• Inhaled insulin
• When do diabetic individuals require insulin therapy?

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Groups of insulin

In the past, the insulin used was derived from animal sources in particular porcine and beef. With the advance in biotechnology, human insulin with various duration of action is now widely available. Insulin is administered by means of a subcutaneous injection, e.g. beneath the skin. Recently, insulin which is delivered via an inhaler has been approved by FDA (see inhaled insulin below).

Table below shows different groups of insulin currently available:

Rapid-acting (clear) conventional insulin is usually given half an hour before a meal. However the very short acting insulin analogue can be given 5-10 mins before a meal. It begin to act about 15 minutes after being injected and reach the peak of activity in one hour.

The intermediate or long acting insulin (cloudy) can be given once daily, or in combination with oral medications or short-acting insulin.

Insulin injection sites

Other than the recently approved inhaled insulin, all insulins given to treat diabetes have to be given subcutaneously, i.e. beneath the skin. The insulin is then absorbed into the circulation in order for it to work.

The location of injection site slightly influences the rate of absorption with abdominal area being the fastest.

The most common injection sites are abdomen, thighs, upper arms, and buttocks as shown in the diagram.

Inhaled insulin

Inhaled insulin has recently approved by the FDA in January 2006 for treatment of diabetic individuals who require insulin therapy. This first inhaled version of insulin is called Exubera from Pfizer Inc. Several trials have shown that the inhaled insulin is as effective as multiple insulin injections therapy. There is no significant difference in blood glucose control between the group using inhaler and patients using needles. But patient satisfaction and quality of life improved dramatically for those who were taking the insulin inhalers. It would be appropriate for those who have needle phobia.

The new portable aerosol delivery system is similar to an asthma inhaler. It delivers a short-acting powder form of insulin into the lungs within minutes. It is to be taken before each meal. However, a long-acting insulin still needs to be given each day by injections. Furthermore it may be less effective during pneumonia or may work differently in those with chronic lung disease e.g. asthma and chronic obstructive pulmonary disease, or who smoke. Reported side effects include coughing, shortness of breath and dry mouth. Safety concerns remain an issue due to a lack of long-term experience with insulin inhaler.

When do diabetic individuals require insulin therapy?

Type 1 Diabetes

There is an absolute lack of insulin in type 1 diabetic patients. The treatment of type 1 diabetes is therefore insulin for life.

Type 2 Diabetes

Type 2 diabetic patients require insulin therapy either long term or short term in the following conditions:

• Long term insulin treatment is needed when oral hypoglycaemic agents fail to control the blood glucose e.g. fasting blood glucose >6.0 mmol/l (110 mg/dl), HbA1c (A1c) >7.5% or already on maximum dose of oral medications.
• Short term insulin treatment is required in type 2 diabetes during acute illness, stress, emergency, surgical operation.
• In child bearing age type 2 diabetic women, insulin should be given before and during pregnancy to ensure excellent blood glucose control.

Insulin therapy in type 2 diabetes should be started early. Sometimes in early stage, the use of combination therapy may be required to achieve good blood glucose control (day time oral agents plus long acting insulin pre-bed). Introduce morning insulin only when daytime blood glucose level is high despite normal fasting blood glucose level. If the diabetes control remains poor, the patients may require full insulin treatment as in type 1 diabetes.