Biguanides contraindications

Metformin is a biguanide used to treat diabetes mellitus. It is contraindicated in patients undergoing general anaesthesia since anaesthesia can interfere with renal function. The risk of lactic acidosis associated with metformin increases in patients with renal impairment. Metformin should be stopped before and during surgery where anaesthesia is indicated. Metformin should only be restarted after the renal function has returned to normal. 

Metformin, a biguanide derivative, can lower excessive blood glucose levels, provided that insulin is present Metformin does not stimulate insulin release. Glucose release from the liver is decreased, while peripheral uptake is enhanced. The danger of hypoglycemia apparently is not increased. Frequent adverse effects include anorexia, nausea, and diarrhea Overproduction of lactic acid (lactate acidosis, lethality 50%) is a rare, potentially fatal reactioa Metformin is used in combination with sulfony-lureas or by itself. It is contraindicated in renal insufficiency and should therefore be avoided in elderly patients. 

Biguanide drugs are contraindicated in patients with renal disease, alcoholism, hepatic disease, or conditions predisposing to tissue anoxia (eg, chronic cardiopulmonary dysfunction) because of an increased risk of lactic acidosis induced by biguanide drugs. 

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