Biguanide
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Biguanides (ATC A10 BA) form a class of oral hypoglycemic drugs used for diabetes mellitus or prediabetes treatment.
Examples of biguanides:
- metformin - widely used in treatment of diabetes mellitus type 2 combined with obesity
- phenformin - withdrawn from the market in most countries due to toxic effects
- buformin - withdrawn from the market due to toxic effects
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[edit] History
Galega officinalis was used for diabetes treatment in traditional medicine for centuries. In the 20s, guanidine compounds were discovered in Galega extracts. It was showed that in animals they lower blood glucose. Some less toxic derivates synthalin A and B were used for diabetes treatment but after the discovery of insulin they were forgotten for several next decades. Biguanides were reintroduced into Type 2 diabetes treatment in the late 50s. Initially phenphormin was widely used but its potential for sometimes fatal lactic acidosis resulted in its withdrawal from pharmacotherapy in most pharmacopeias (in the US in 1977). Metformin has much better safety profile and it is the principal biguanide drug used in pharmacotherapy worldwide.
[edit] Pharmacotherapy
Biguanides do not affect the output of insulin, unlike other hypoglycemic agents such as sulfonylureas and meglitinides. Therefore, they are not only effective in Type 2 diabetics, but they can also be effective in Type 1 patients in concert with insulin therapy.
[edit] Mode of action
The exact mode of action of biguanides is not fully elucidated. However, in hyperinsulinemia, biguanides can lower fasting levels of insulin in plasma. Their therapeutic uses spawn from their tendency to reduce gluconeogenesis in the liver, and as a result, reduces the level of glucose in the blood. Biguanides also tend to make the cells of the body more willing to absorb glucose already present in the blood stream, and there again reducing the level of glucose in the plasma.
[edit] Side effects and toxicity
The most important and serious side effect is lactic acidosis. Phenformin and buformin are more prone to cause acidosis than metformin therefore they have been practically replaced by it. Another potential side effect is diarrhea. However, when metformin is combined with other drugs (combination therapy), hypoglycemia and other side effects are possible.
