Biguanides: Metformin

Metformin is the first line therapy for treatment of patients with type 2 diabetes.

Metformin belongs to a class of drugs called biguanides and is the only drug of this class currently available. Metformin has been available in Europe for decades, but was only approved by the FDA for use in the United States in 1995.


How Does Metformin Work?

Exactly how metformin works is not well understood but the primary effect of metformin is that it inhibits the liver’s production of glucose and, possibly, stimulates the process of transporting glucose into muscle, a process that requires insulin.

Metformin is useful for patients who are obese because it does not cause the weight gain seen with other diabetes therapies like sulfonylureas (glyburide, glipizide and glimepiride) and it may even bring about some degree of weight loss.

Metformin is also as effective as sulfonylureas in reducing HbA1c (1.5-2%). Just like with sulfonylurea treatment, the overall magnitude of response to metformin is directly related to the starting fasting plasma glucose concentration.


Metformin Side Effects

Metformin side effects can be a problem. Up to 30% of patients develop gastrointestinal complaints, though these may be mild and temporary, especially if the drug is started at low doses and increased slowly. The largest concern with metformin side effects is the potential to produce a build up of lactic acid. However, this is a very rare side effect of the drug, particularly if the drug is not prescribed when it is contraindicated. Contraindications for this drug include evidence of kidney disease, significant liver disease, chronic alcoholism or congestive heart failure. The big advantages of metformin is that it does not generally cause hypoglycemia and, again, it does not lead to weight gain.

Read About Other Type 2 Diabetes Treatments:

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 Reviewed by Dr. Mariela Glandt, Apr. 2013

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