For many people with type 2 diabetes, the drug of choice is likely to be metformin (Glucophage), the only available member of the biguanide family. It works by stopping the liver from producing new glucose and by allowing insulin to more effectively deliver glucose to the muscle cells. It is often used by overweight diabetics because the sulphonylureas, the other family of drugs used to treat type 2 diabetes, can encourage weight gain.
However, metformin can build up in the bloodstream, resulting in lactic acidosis (a life threatening condition caused by too much lactic acid). In its first year on theUS market, there were 47 cases of lactic acidosis and 20 deaths (N Engl J Med, 1998; 338: 265-6). Even now in Australia, the Adverse Drug Reactions Advisory Committee (ADRAC) says it has received 48 reports of lactic acidosis with metformin, including 15 deaths (Aust Adverse Drugs React Bull, 2001; 20, no 1).
The use of metformin in a five year trial was associated with a 42 per cent increased risk of death, and showed that metformin significantly increased mortality rates in diabetic patients who also had coronary heart disease (Cardiology, 1999; 91: 195-202).