Diabetic Medications - Drugs

In the management of diabetes mellitus, the control of blood glucose level is central and one of the major ways this is achieved is the use of oral diabetic drugs. Generally, they act by lowering the glucose level in the blood; hence they also go by the name “oral hypoglycemic agents.”

The clinically approved hypoglycemic agents are of various types and are classified based on their mechanisms of action.

The hypoglycemic drugs are the main stay of management of type II diabetes.

Classifying hypoglycemic drugs

Sulfonylureas: These were the first drugs used clinically to lower blood glucose levels. The older drugs in this category are called “first generation sulfonylureas” while the newer drugs are referred to as “second generation.”

The sulfonylureas directly stimulate the beta cells of the pancreas to produce insulin. The insulin released then drives the glucose in the blood into peripheral tissues thereby, reducing the blood glucose level.

In type I diabetes, there is an absolute deficiency of insulin, most times due to a destruction of the beta cells of the pancreas. In type II diabetes, the beta cells either produces too little insulin or produces insulin to which the cells of the body are non responsive (insulin resistance). Sulfonylureas cannot be used in type I diabetes, in conditions where inert insulin is being produced or in gestational diabetes.

The sulfonylureas work best with patients over 40 years of age, who have had diabetes mellitus less than 10 years.

These drugs are so effective in lowering blood glucose that it’s not surprising that the major side effect of their use is hypoglycemia.

Biguanides: Biguanides function by reducing hepatic glucose production and at the same time increasing the uptake of blood glucose by the peripheral tissues such as skeletal muscles.

The only biguanide in clinical use today is metformin.

Thiazolidinediones: Drugs in this group act by increasing the sensitivity of the peripheral tissues to insulin. On their own, they do nothing to the level of insulin secretion by the beta cells of the pancreas. In type II diabetes in which there is reduced sensitivity of the peripheral tissues to insulin, the thiazolidinediones work to reduce this state of insulin resistance.

Meglitinides: The drugs in this group are closely related to the sulfonylureas. They are usually taken 30 minutes before eating a meal. The meglitinides boost the insulin response to each meal by stimulating a shorter but more intense insulin release. This is very useful in the regulation of post prandial blood glucose levels in type II diabetes.

Alpha glucosidase inhibitors: Monosaccharides such as glucose are the end product of carbohydrate digestion. For absorption of glucose to take place, the body releases an enzyme, alpha glucosidase. The enzyme facilitates the absorption of glucose into the blood stream.

Controlling the post prandial blood glucose level is important in preventing hyperglycemia in a diabetic after a meal has been taken. This control is what meglitinides and the alpha glucosidase inhibitors achieve.

In the case of the latter, they inhibit the alpha glucosidase enzymes and are therefore, able to reduce the rate at which glucose from the intestines enter into the bloodstream.

The above are the commonest oral hypoglycemic agents in use but there are a few others used clinically and much more that are still experimental.

The table below lists a few examples of drugs belonging to the various classes of hypoglycemic agents discussed above:

Diabetes Drugs	Examples
Sulfonylureas	Chlorpropamide, glibenclamide, glimepiride, glipizide, tolazamide, tolbutamide
Biguanides	Metformin
Thiazolidinediones	Pioglitazone, Rosiglitazone, Troglitazone
Meglitinides	Nateglinide, Repaglinide, Mitiglinide
Alpha glucosidase inhibitors	Acarbose, Miglitol

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