Phenformin-associated lactic acidosis: pathogenesis and treatment.

Since phenformin's introduction into clinical medicine, a total of 552 cases of lactic acidosis have been reported in patients taking this hypoglycemic agent. In 306 cases, sufficient documentation was available to establish the diagnosis with reasonable certainty (blood lactate, 6 meq/litre or greater, and blood pH, 7.33 or less). The mortality rate among insulin-treated patients (15%) was considerably less than the mortality rate in the group as a whole (42%). Taken together with results from animal studies, these data suggest that insulin is the treatment of choice for phenformin-associated lactic acidosis. Sodium bicarbonate should be administered to patients with severe acidosis, but should be withheld from patients with mild acidosis. Overly aggressive administration of sodium bicarbonate can be deleterious and should be avoided. Although dialysis has been suggested by some authors for the treatment of phenformin-associated lactic acidosis, the mortality rate among dialyzed patients (48%) was roughly the same as for the group as a whole (42%).