LACTIC-ACIDOSIS RATES IN TYPE-2 DIABETES

OBJECTIVE - To provide a context for the interpretation of lactic acid osis risk among patients using metformin, we measured rates of lactic acidosis in patients with type 2 diabetes before metformin was approve d for use in the U.S. RESEARCH DESIGN AND METHODS - Using electronic d atabases of hospital discharge diagnoses and laboratory results mainta ined by a large, nonprofit health maintenance organization (HMO), we i dentified possible lactic acidosis events in three geographically and racially diverse populations with type 2 diabetes. We then reviewed ha rd-copy clinical records to confirm and describe each event and determ ine its likely cause(s). RESULTS - From >41,000 person-years of experi ence, we found four confirmed, three possible, and three borderline ca ses of lactic acidosis. In each case, we identified at least one sever e medical condition that could have caused the acidosis. The annual co nfirmed event rate is similar to published rates of metformin-associat ed lactic acidosis. CONCLUSIONS - Lactic acidosis occurs regularly, al though infrequently, among persons with type 2 diabetes, at rates simi lar to its occurrence among metformin users. The medical conditions wi th which both metformin-associated and naturally occurring lactic acid osis co-occur are also its potential causes. The observed association between metformin and lactic acidosis may be coincidental rather than causal. This possibility merits further study.