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Diabetes Mellitus: Clinical Significance Of Insulin Therapy, Its Indications And Commercially Available Variants

Updated on February 17, 2014

Insulin Injection

Source

Insulin Usage

Presently available insulin is made chiefly from beef or pork pancreas after various chemical processes for purification. Recently, insulin exactly resembling human insulin has been synthesized from pork insulin. It is also manufactured by recombinant DNA technology using E.Coli and these preparations are available on a limited scale. Insulin derived from different sources is similar in action but due to the presence of exogenous substances, which alter the action of insulin, different preparations vary in biological activity. Allergic reactions are caused either by the sensitization to insulin or the impurities. Adverse local effects comprise insulin lipotrophy and rarely lipohypertrophy. Purified preparations being more effective and less antigenic are preferable.

Monocomponent insulins are produced from crude insulin by sephadex gel chromatography, which separates the compound into three peaks (components). The first peak, (A) consists of proinsulin and the last peak (C) consists of insulin and related peptides. The insulin is separated and these are available for regular use now.

Indications Of Insulin Use

The duration of action of insulin depends upon the preparation and the site of administration. Usually, insulin is given subcutaneously, using a 24 or 25 needle. Intramuscular or intravenous administration causes more rapid effect.

Soluble insulin is effective for a few hours if given intramuscularly and only for a few minutes if given intravenously. The long- acting insulins are not given intravenously. For long term therapy, the patient should be taught to inject himself.

Absolute indications for insulin:

  1. Insulin- dependent diabetes mellitus (IDDM)
  2. Diabetic ketoacidosis,
  3. Lactic acidosis,
  4. Hyperosmolar coma,
  5. Infective complication,
  6. Gestational diabetes, and
  7. Surgery and anaesthesia.

Relative Indications:

  1. Maturity onset diabetes not responding to diets and oral drugs,
  2. Presence of contraindications to oral hypoglycemic agents, and
  3. Brittle diabetes.

Commercially Available Insulin

Type of Insulin
Source
Maximum action (hrs)
Duration of action (hrs) in Subcutaneous Administration
Purity
Type Of Action
SOLUBLE INSULINS
 
 
 
 
 
1. Regular Insulin
Beef
4 to 8
8 to 12
purified
Fast and short
2. Actrapid MC
Pork
4 to 8
8 to 12
purified
Fast and short
3. Isophane Insulin NPH
Beef
8 to 12
18 to 28
purified
Intermediate
INSULIN ZINC SUSPENSIONS
 
 
 
 
 
4. Semilente
Beef
8 to 10
12 to 16
purified
Intermediate and slow
5. Lente
Beef
6 to 12
24 to 30
purified
Intermediate and slow
6. Ultralente
Beef
7 to 10
24 to 36
purified
Intermediate and slow
7. Semitard MC
Pork
 
 
purified
 
8. Monotard MC
Pork
 
 
purified
 
9. Protamine Zinc Insulin
Beef
10 to 24
24 to 36
purified
Slow and prolonged (Weak)

The Insulin Pump

Source

The Insulin Therapy

Except in emergencies, insulin therapy is started after prescribing the diet and making sure that the patient complies with the diet. The starting dose is 8- 12 units every 8 hours by subcutaneous injections, the dosage being adjusted so that the peak action coincides with the peak blood sugar levels. Best parameter for monitoring diabetic control is blood sugar, since the urine sugar may not always reflect the blood sugar levels. If urine examination is resorted to, it should be ensured that the urine tested should be the one formed during the time of the test. Urine collected in the bladder for long periods should be avoided. At present, methods are available to enable the patients themselves to test blood sugar from finger prick blood in their homes. The dose of insulin is adjusted depending upon the blood or urine sugar levels. If the postlunch specimen is showing hyperglycemia, the morning dose should be increased and if the early morning specimen is showing hyperglycemia, the evening dose should be increased.

If hypoglycemia occurs during the day, the previous dose should be reduced. After finding out the total daily requirement of insulin for a predetermined diet, the whole dose can be given as a single injection consisting of either one of the long-acting insulins or a combination of soluble and NPH or soluble and protamine zinc insulins in the proportion of 1- 3. Blood sugar profiles for the whole day are obtained by taking fasting, postlunch, predinner and midnight samples of regular intervals to ensure that control of blood sugar is adequate. Some cases may require an additional dose of soluble insulin before the evening meal. Only general principles can be laid down and in all cases, the ideal dose and timing should be achieved by trial and error.

For patients who are not acutely ill, treatment can be started on medium- acting insulins like NPH or lente, given before breakfast and further adjustments are done as required. Care should be taken to prevent contamination of soluble insulin with the long acting preparations when using drug combinations. Addition of protamine and zinc alters the properties of soluble insulin. For proper drug compliance, the technique or sterilization of the needle and injection should be taught to the patient. The common sites for injection are the anterior aspect of the lower third of the thigh or anterior abdominal wall. The site of injection should be changed regularly to avoid thickening of the skin and local fat atrophy (insulin lipodystrophy). Loss of potency can be minimized by storing the insulin in a refrigerator in darkness.

© 2014 Funom Theophilus Makama

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