Metformin causes I severe, sometimes life-threatening side effect of lactic acidosis. All of the following factors increase the risk of lactic acidosis except:
(A) Advanced age (B) Smoking (C) Liver dysfunction (D) Renal failure
(B) Ans: B. Smoking(Ref Goodman Gilman 12/e p1259; Katzung I 3/e p736-737, 12/e p75)Smoking does not increase lactic acidosis risk in patients taking metformin.Lactic acidosis & metformin:Metformin use in patients with concurrent conditions with poor tissue perfusion (sepsis, myocardial infarction, CHF & enal failure).Decreased GFR - Increases plasma metformin levels - By reducing drug clearance from circulation.Metformin - ContraindicationsSevere pulmonary disease.Decompensated hea failure.Severe liver diseaseChronic alcohol abuse.Renal disease.Conditions predisposing to tissue anoxia (e.g., chronic cardiopulmonary dysfunction) - Due to increased lactic acidosis risk.