Insulin, the centerpiece of three Nobel prizes in medicine, can aptly be called the ‘molecule of the millennium’. Needless to mention it has saved millions of diabetics since its usage started in 1923. For individuals diagnosed with diabetes, comprehending the role, types and application of insulin therapy is vital in controlling blood sugar levels and maintaining a healthy lifestyle. This article aims to give a comprehensive about the insulin therapy in diabetes management with various types of insulin, dosage considerations, administration methods and advancement fields in insulin therapy in diabetes.
Indications of Insulin Therapy in Diabetes:
- Type 1 diabetes
- Oral antihyperglycemic agent failure (primary and secondary)
- Gestational diabetes
- Emergencies in diabetes (surgery, diabetic ketoacidosis, hyperosmolar nonketotic coma etc)
- Serious infection, liver disease, advanced kidney disease etc
The Type 1 diabetes patients are totally dependent on insulin for survival. And most of the Type 2 diabetes patients need insulin injection to maintain euglycemia years after diagnosis. And insulin therapy in diabetics provides benefit which goes beyond glucose control. And hence, early initiation of insulin is the norm of the day.
In pregnant women with diabetes, sulphonylureas are contraindicated and insulin is essential in controlling blood glucose. All diabetes, irrespective of their types must be put on insulin whenever they require surgery, or develop ketoacidosis or hyperosmolar nonketotic coma.
Goal of Insulin Therapy in Diabetes:
The goal of insulin therapy in diabetes is to mimic the natural secretory profile of the insulin in vivo in a normal person. Normally insulin is secreted in two phases; a continuous low secretion phase and a post-meal high secretion phase. To mimic these two types of insulin secretory pattern, there are three types of insulin according to the onset and duration of action.
Types of Insulin:
- The first variety is short acting insulin. The classical example of this class of insulin is soluble insulin or regular insulin which has onset of action by 15 to 30 minutes and duration of action 4 to 6 hours.
- The next variety is intermediate acting insulin. The commonly used NPH insulin is of this variety with onset of action 2 to 3 hors and duration of 8 to 12 hours. The Lente insulin is also of this class with the onset of action by 1 to 3 hors and duration of 8 to 14 hours.
- Long acting insulin, such as insulin glargine or detemir, have a slow, steady release and can provide coverage for an entire day or longer.
- Insulin is also marketed as a mixture of two different types of insulin, e.g a combination of regular insulin and NPH insulin in a fixed dose combination of either 30% : 70%, 25% : 75% and 50% : 50% proportion.
- Insulin can be injected in various sites. It may be given in subcutaneous tissues (commonest site), intravenously, intraperitoneally and rarely intramuscularly.
Difference Between Animal Insulin and Human Insulin:
Insulin can be classified according to the source. Insulin is procured from animal sources, e.g from cows (bovine insulin) and pigs (porcine insulin). Insulin can also be manufactured by the DNA technology and thus we can procure human insulin by this method. There are structural differences in the human and animal insulin, and they also differ by the immunogenicity. The animal insulin provokes the formation of anti-insulin antibody. These anti-insulin antibodies can lead to allergic reactions and also will bind with the injected insulin making them ineffective.
What are the Regimens of Insulin Injection:
The dose of the insulin therapy in diabetes that one needs depend on the ‘insulin demand’ of the patient at that point of time, which changes with time and clinical condition. There is neither any fixed dose that can be prescribed in insulin therapy in diabetes management. The requirement of the dose needs to be assessed by regular blood glucose monitoring. It is important to note that determination of the dose requirement of insulin therapy in diabetes cannot be done by urine glucose monitoring which is not only wasteful but also unscientific. A useful starting dose is approximately 0.3 to 0.6 unit/kg body weight which should be divided into two or three parts according to the regimen followed.
Various types of insulin injection regimens are in vogue to suit the need of the patient.
- Twice daily mixed insulin regimen: This is the most common regimen of insulin therapy in diabetes used both in Type 1 and Type 2 diabetics. It is a mixture of soluble and NPH or Lente insulin. The mixture may be available as a premixed fixed ratio (30 : 70, 25 : 75 or 50 : 50) or may be made according to the need by mixing the two different types of insulin in the same syringe. The regimen is meant to cover the two meals of the day i.e breakfast and dinner with short acting insulin (regular) and the cover for the lunch and the basal insulin demand by the intermediate acting insulin. The fixed dose combinations are very popular.
- Multiple subcutaneous insulin injections: Most commonly required in Type 1 diabetics. It was shown by important clinical studies that this regimen is most effective in achieving normalization of blood glucose level in both Type 1 and Type 2 diabetics. Here, regular insulin is injected in three or four pre-meal situations and the basal insulin requirement is delivered by a night-time long acting insulin injection.
- Bedtime insulin and daytime sulfonylurea: Quite useful in Type 2 diabetics, as delivering the basal insulin requirement at night and covering the mealtime demand by the oral hypoglycemic agents achieve the target blood glucose values in may cases. Effective in Type 2 diabetics with a significant beta-cell reserve.
Insulin Injection Methods:
- Short acting insulin e.g. regular insulin should be injected 20 to 30 minutes before the meal.
- The injection should be given only in the designated areas e.g. lower abdomen, upper lateral aspect of thighs, buttocks, upper arms. No subcutaneous injection to be given on the forearms.
- It is preferable t use disposable plastic syringes to avoid the need of washing and sterilizing the glass syringes. Disposable syringes can be reused several times before they become too blunt.
- The area of injection need not be cleaned with alcohol, provided the patient maintains his/her personal hygiene properly. In case alcohol is used it should be ensured that the alcohol is dried completely before the injection.
- The skin should be pinched up and the needle is to be inserted nearly vertically upto the hilt of the needle.
- The site of the injection should be rotated regularly within the same anatomical site-like, if the morning dose is given in the abdomen and the evening dose is given on the thigh, change of site should be another part of abdomen in the morning and another site of thigh in the evening.
- When two different types of insulin are mixed in the same syringe, the regular insulin should be drawn first followed by the NPH or Lente.
How to Use Insulin Pen Injection:
The Injection Device Used in Insulin Therapy in Diabetes:
The standard syringe and needle is the most commonly used device for the injection of insulin. However, now-a-days, ‘pen devices’ has made a foray into the market. The pen devices contain the insulin in a cartridge (which is disposable) and the dose is ‘dialed’ by rotating the body of the pen.
Advantages of Pen Devices:
The main advantages of these pen devices are that they are convenient, easy to carry the insulin out of home without the need to carry syringes and vials, obviating the need to draw insulin in syringe thereby removing the chances of error. Moreover, when the patient is on the move, the preservation of the insulin is not an issue, as insulin inside the pen device is safe from degradation. All these factors increase the acceptability and convenience of the patient for self injection.
Some Other Insulin Injection Devices:
There are other devices for the insulin delivery e.g. Jet injector, where insulin is ejected as spray droplets under very high pressure and they penetrate the skin and get deposited in subcutaneous tissue and thereby injection is made without a needle. These are useful in patients wo have got unusual needle phobia.
Insulin also can be delivered by a insulin pump which gives a continuous subcutaneous insulin infusion and are useful in Type 1 diabetics and brittle Type 2 diabetics with extreme fluctuations of dosage.
Recent Development in Insulin:
Recently, novel types of insulin are being designed by scientists by slightly changing the amino acid structure of native insulin molecule to cater to the special needs. Insulin Lispro and Aspart are two ultra-short acting insulins which have the property of controlling the postprandial blood glucose with reduced incidence of hypoglycemia. Insulin Glargine is genetically modified insulin that has got very long duration of action and can serve as an ideal basal insulin.
Insulin is usually administered by injection only. But newer vistas of research are concentrating on the alternate modes of delivery of insulin to improve patient compliance, e.g insulin by inhalation or insulin by oral routes. All these developments are opening up newer frontiers in the insulin therapy in diabetes management.
Some Myths Associated with Insulin Injection:
- The patient may be put on insulin on a temporary basis (to combat the glucotoxicity) to achieve euglycemia. So it may not be true that “once on insulin, always on insulin”. Insulin used during surgery, emergencies, pregnancy and during many infections (like tuberculosis) is a temporary use. Many of these patients respond adequately on OAHAs later on.
- Insulin use should not be equated with a poor prognosis. It is true that insulin is added to the therapeutic regimen as a last resort for control of hyperglycemia in type 2 diabetics after adequate trials of OAHAs are done. Burt insulin can be and should be started early in all such patients without wasting much time on the trial of OAHAs, because most of these patients who are responding sub-optimally on the oral agents would require insulin. So sooner the better.
- Insulin is as commonly associated with hypoglycemia as are oral agents (particularly the sulfonylureas). So the fear of hypoglycemia is not an adequate excuse to deny the patient the benefit of insulin therapy. Moreover, the hypoglycemia resulting from insulin therapy is easier to handle as they are shorter lasting compared to the hypoglycemia resulting from oral agents which are longer acting and thereby the chances of recurrent hypoglycemia are there.
What are the Sick Day Rules in Insulin Therapy:
Insulin should not be omitted during ‘sick days’. During the sick days, the insulin resistance (and hence insulin demands) increases. In fact, if insulin is omitted during the sick days, the change of developing ketosis is high. If the patient is ill because of fever, diarrhea, vomiting etc. and can’t take his/her usual meals, the dose of the insulin may need to be reduced and longer acting preparations of insulin are to be discontinued and shorter acting agents e.g. regular insulin should replace the longer acting ones.
In the journey of managing diabetes, insulin therapy in diabetes management plays a significant role. Understanding the types f insulin therapy, methods of administration, dosage considerations and latest medical devices empower individuals to take charge of their health. Consulting healthcare professionals and staying under their instructions, the insulin therapy can be pivotal in optimizing diabetes management and improve the quality of life for diabetics patients.
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