Biguanide-induced lactic acidosis in Finland.

Twenty-four patients with biguanide-induced lactic acidosis were reported to the Adverse Drug Reaction Register of the Finnish National Board of Health from 1974-1977. Of them, 23 had been treated with phenformin and one with metformin. The mean age of the patients was 71 years, and all but one were more than 65 years of age. The mortality rate was 63%. One patient had cirrhosis of the liver and one was already known tohave had impaired renal function. Fourteen of the patients had a normal serum creatinine concentration either before or after the development of lactic acidosis. Thus, in most patients it had not been possible to prevent development of lactic acidosis by observing the contraindications to biguanide therapy. Most patients had some form of co-existing cardiovascular disease. Tetracycline therapy was a probable precipitating factor in three cases. Based on the statistics of biguanide consumption in Finland, the annual incidence of biguanide-induced lactic acidosis in 1976 and 1977 was between 1/2000 and 1/3000 and that of fatal lactic acidosis was 1/4000.