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ORGANIZATION OF CLASS
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A high level of glucose stimulates an increase in insulin release from β cells of the pancreas. Insulin then drives carbohydrate into cells. Patients who have high glucose levels in their blood are said to have diabetes mellitus.
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Of course, you remember that diabetes mellitus is divided into two groups: type 1 (insulin dependent) and type 2 (insulin resistant). These distinctions are important for pharmacology because they make it easier to remember the mechanism of action of the drugs used to treat diabetes mellitus.
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As an aside, there is another form of diabetes that students sometimes confuse with diabetes mellitus and that is diabetes insipidus. Diabetes insipidus is a disorder of water and sodium balance. Generally, if someone says diabetes, they mean the sugar-related (mellitus) disease and not diabetes insipidus.
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But let’s return to the topic at hand.
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Type 1 diabetes is related to loss of insulin-secreting cells in the pancreas. Type 2 diabetes is related to target cell resistance to the action of insulin.
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This, of course, is somewhat simplified. An endocrinologist would cringe. Patients with type 1 diabetes are dependent on an exogenous (outside the body) source of insulin. This disorder generally appears in childhood; hence, the former term for it is juvenile diabetes. Type 2 diabetes has been called adult-onset. It appears to have a genetic basis, and patients are often obese. Patients with type 2 diabetes are treated with oral agents that lower blood glucose (hypoglycemics) and with insulin.
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So, that said, we should organize our drugs into insulins and the oral hypoglycemic agents.
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Insulin is a small protein that is synthesized and secreted by the β cells of the pancreas. Insulin for replacement therapy can be isolated from animal sources. Human insulin is made using recombinant DNA technology.
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INSULIN must be administered by injection and doses are expressed in international units of activity.
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All peptides are degraded by enzymes in the gastrointestinal (GI) tract, so it is not possible to administer insulin by the oral route. Given intravenously, it has a half-life of less than 10 minutes (short). Therefore, it is administered subcutaneously.
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The most common adverse effect of insulin is hypoglycemia.
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I hope that this is intuitively obvious.
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Insulin preparations vary in their time to onset and duration of action.
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The onset and duration of action of the insulin preparations are controlled by the size and composition of the crystals in the particular insulin preparation.
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