Type 2 diabetes is one of the four disease states of diabetes mellitus, a condition characterized by chronic elevation of blood glucose due to a defect or deficiency of the insulin-secreting cells of the pancreas. Type 2 diabetes pertains to the resistance of organs or tissue to the action of insulin in addition to a relative reduction in its secretion. Normally, organs like the liver and muscles respond to insulin secretion, but in type 2 diabetes, the insulin is not taken up-and the glucose in the blood is not stored or metabolized. Thus, even if there is insulin produced, the organs lack the ability to use them.
It is thought that only about 30% of patients with type 2 diabetes require exogenous insulin to survive. The rest however, need supplementation and glycemic control to prevent the debilitating effects of type 2 diabetes. There are numerous oral antidiabetic agents available in the market today, but the traditional medications of choice for type 2 diabetes include those under the sulfonylurea and biguanide group.
Metformin is the only drug classified under biguanides. An older drug, Phenformin, has since been phased out due to its lactic acidosis effects and lack of long term benefit despite regular use. Metformin use in type 2 diabetes is essentially for decreasing the production of glucose in the liver thus reducing its output in the bloodstream. Other possible actions of metformin involve blocking sugar production in the kidneys, slowing its absorption in the intestines, increasing glucose breakdown in tissues and rapid removal from the blood. The medication may be taken alone but patients with type 2 diabetes are usually prescribed a combination of biguanides plus other oral antidiabetic agents like sulfonylureas and thiazolidinediones.
Since metformin controls blood sugar, hypoglycaemia may be an expected side effect. However, actual studies have not come up with concrete evidence to say that it can cause hypoglycaemia. The common toxic effects of metformin include gastrointestinal upset, anorexia, nausea, vomiting, and diarrhea. These are often observed during the start of medication and are often transient and harmless. There are a small population of patients who develop persistent diarrhea, in which case medication should be stopped and changed. Vitamin B12 deficiency may also arise in chronic or long term metformin treatment; hence patients with type 2 diabetes taking it should be screened for vitamin B12 levels every year. Vitamin B12 deficiency itself is detrimental, since nervous system damage can be severe and irreversible.
Another thing that must be noted in metformin use is its potential to cause lactic acidosis. Lactic acidosis arises from the drug’s action on the cells of the intestines, inducing them to convert the glucose to lactate. The increased lactic acid in the blood stream can produce symptoms such as nausea, vomiting, hyperventilation, abdominal pain, and lethargy. Individuals who have comorbid conditions in addition to type 2 diabetes should therefore be wary in using metformin as part of their treatment. Especially susceptible individuals include those who have kidney problems, liver disease, and chronic alcoholism.