Biguinides

They potentiate the hypoglycemic action of insulin and sulphonyl ureas but they don’t produce clinical hypoglycemia in diabetics.

Biguanides include drugs like metformin and phenformin.

Mechanism: They do not stimulate the release of insulin. They increase glucose uptake in skeletal muscle, and have effects on glucose absorption and hepatic glucose production. They also enhance anaerobic glycolysis.

Pharmacokinetics: Phenformin and metformin are rapidly absorbed from the gastrointestinal tract. Metformin is largely excreted unchanged in the urine and has a longer duration of action.

Side effects: Nausea, vomiting, anorexia, diarrhea, abdominal cramp, lactic acidosis (esp. phenformin).

Use: Obese diabetics (uncontrolled by diet alone), Supplement to sulphonyl urea.

Contraindication: Diabetes with hepatic, renal insufficiency, In IDDM, NIDDM (with infection, fever, surgery) and during pregnancy.

They have no value in diabetes complicated by acidosis or coma.