Which of the following characteristics make metformin a preferred biguanide than phenformin?: (A) It is more potent, (B) It is less liable to cause lactic acidosis, (C) It does not interfere with vitamin B12 absorption, (D) It is not contraindicated in patients with kidney disease
Answer is B. (Ref: KDT 6/e p269) Incidence of lactic acidosis is more with phenformin and that of megaloblastc anemia (due to interference with vitamin B12 absorption) is more with metformin.