The Food and Drug Administration's Adverse Event Reporting System is the primary surveillance database used for the identification of safety problems of marketed drugs. Despite the limitations of underreporting, differential reporting, and uneven quality, submitted reports often allow the identification of serious adverse events that are added to the product labeling information. In rare instances, additional regulations, up to and including market removal, have been required. We encourage physicians, pharmacists, other health care professionals, and patients to continue to report serious suspected and known adverse drug reactions to manufacturers and the Food and Drug Administration.

From 1980 through 1995, the incidence rate of lactic acidosis was 9 per 100,000 person-years (95% CI 0-21) in patients dispensed metformin in Saskatchewan, Canada. This incidence rate was derived from a population with complete ascertainment of hospitalizations and deaths associated with lactic acidosis in metformin users. It is similar to previously published rates based on passive reporting of cases, and it is well below the lactic acidosis rate of 40-64 per 100,000 patient-years in patients prescribed phenformin.

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Since 2003, the number of adult antidiabetic drug users increased by 42.9% to 18.8 million in 2012. Metformin use increased by 97.0% to 60.4 million prescriptions dispensed in retail pharmacies in 2012. Among antidiabetic drugs newly approved for marketing between 2003 and 2012, the dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin had the largest share with 10.5 million prescriptions in 2012. Rosiglitazone use plummeted to <13,000 prescriptions dispensed in retail or mail-order pharmacies in 2012. Concomitancy analyses showed that 44.9% of metformin use was for monotherapy. Between 33.4 and 48.1% of sulfonylurea, DPP-4 inhibitor, thiazolidinedione, and glucagon-like peptide 1 analog use was not accompanied by metformin. CONCLUSIONSThe antidiabetic drug market is characterized by steady increases in volume, and newly approved drugs experienced substantial uptake, especially DPP-4 inhibitors. The use of rosiglitazone has been negligible since restrictions were put in place in 2011. Further study is needed to understand why one-third to one-half of other noninsulin antidiabetic drug use was not concomitant with metformin use despite guidelines recommending that metformin be continued when other agents are added to treatment.In 2010, 18.8 million adults in the U.S. had been diagnosed with diabetes mellitus, 7.0 million additional Americans were affected by undiagnosed diabetes, and an estimated 1.9 million adults received a new diagnosis of diabetes during that year (1). The number of Americans with diabetes who have or have not received a diagnosis is expected to increase to 44