Pharmacology: Metformin hydrochloride is a biguanide oral antihyperglycemic drug. Metformin hydrochloride does not affect insulin secretion nor the function of pancreatic β-cells. The proposed mechanisms include decreased hepatic glucose production and intestinal absorption of glucose, increased peripheral uptake and utilization of glucose by increasing peripheral tissue sensitivity to and/or receptor binding of insulin. At therapeutic dose, metformin does not cause hypoglycemia in both diabetic or nondiabetic individuals.
When given orally, the bioavailability of metformin is about 50-60% under fasting conditions. Food decreases the rate and extent of absorption. The protein-binding is negligible. Metformin is not metabolized in the body. The elimination t½ is about 6.2 hrs. Up to 90% of the dose is excreted unchanged in urine. Metformin crosses the placenta and appears in breast milk.