Metformin hydrochloride: an antihyperglycemic agent

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosage and administration of metformin hydrochloride are reviewed. Metformin is an antihyperglycemic agent; it lowers the blood glucose concentration without causing hypoglycemia. Proposed mechanisms of action include decreased intestinal absorption of glucose, increased glucose uptake from the blood into the tissues, decreased glucose production in the liver, and decreased insulin requirements for glucose disposal. Metformin is slowly absorbed from the small intestine and does not undergo hepatic metabolism. The half-life is about five hours. The major route of elimination is renal; the drug is contraindicated in patients with impaired renal function. In double-blind, placebo-controlled trials, metformin has shown efficacy in the treatment of non-insulin-dependent diabetes mellitus (NIDDM). The drug is as effective as sulfonylureas in patients with diabetes who are nonobese or obese and whose diabetes is uncontrolled by diet alone. Metformin may be useful as addon therapy in obese patients with diabetes uncontrolled by sulfonylureas and diet. Lipid profiles may be favorably influenced. The most common adverse effects are gastrointestinal. A rare but potentially fatal adverse effect is lactic acidosis. Metformin has the potential to interact with cationic drugs eliminated by the renal tubular pathway. The usual effective dosage is 1.5-2.5 g/day orally in two or three divided doses. Metformin hydrochloride is an effective alternative to sulfonylureas in obese and non-obese patients with NIDDM in whom diet alone has not achieved glycemic control, and it may be useful as addon therapy in patients whose diabetes has not responded adequately to sulfonylureas plus dietary measures.