Metformin

Metformin is an oral drug used in the treatment of diabetes. It is of the biguanide family, and has the rare property, among diabetes treatments, of not causing weight gain or even inducing weight loss.

It is approved as monotherapy as an adjunct to diet and exercise, in combination with a sulfonylurea or a thiazolidinedione, and with a repaglinide or nateglinide. Metformin may also be supplemented with insulin.

Mechanism of action
While the mechanism is not known with certainty, it appears to increase peripheral and hepatic sensitivity to insulin, decreasing hepatic glucose production and increasing insulin-stimulated uptake and utilization of glucose by muscle and fat cells.

Adverse effects
Gastrointestinal side effects are fairly common and do lead to discontinuation in a number of patients.

Lactic acidosis is the most feared complication. It can also exhibit renal toxicity; it may increase the risk of cardiovascular events, although this needs to be traded against the cardiovascular risks of uncontrolled glucose.