Outcomes and costs of different classes of diabetes drugs were compared by studies published in the past month.
An English cohort study with more than 400,000 type 2 diabetes patients looked at the outcomes of amputation, blindness, severe kidney failure, hyperglycemia, and hypoglycemia. The study, published by The BMJ on March 30, focused on 21,308 patients taking glitazones (mostly pioglitazone) and 32,533 patients taking gliptins (mostly sitagliptin) between 2007 and 2015. Use of glitazones was overall associated with reduced risk for blindness, and more specifically, triple therapy with metformin, sulfonylureas, and glitazones was associated with lower risk of blindness compared to metformin monotherapy. Triple therapy with metformin, sulfonylureas, and either glitazones or gliptins was associated with increased risk of hypoglycemia compared to metformin monotherapy, although the risk was about the same as that with metformin/sulfonylurea dual therapy. Overall, glitazones were associated with an increased risk of hypoglycemia and gliptins associated with a reduced risk. Patients on gliptin or glitazone monotherapy had a significantly increased risk of severe kidney failure compared to those on metformin.
The study authors noted that their findings could be affected by confounding variables, for example, that patients who take a drug other than metformin as their first-line medication might do so due to a comorbidity such as renal impairment. The authors attempted to control for such issues, though, and concluded that the study's results could have implications for the prescribing of hypoglycemic drugs, including the finding that “triple therapy involving gliptins or glitazones does not appear to have consistent measurable advantages [on the studied outcomes] compared with dual therapy or monotherapy with metformin.” An accompanying editorialist expressed even greater concern about the potential for confounding, writing, “To my knowledge, no antihyperglycaemic agent has been shown to convincingly reduce the risk of any diabetes related complication to any greater extent than other agents.”
Another study, published as a research letter in the April 5 Journal of the American Medical Association, compared the cost of diabetes medications in the U.S. from 2002 to 2013. Despite adjusting for inflation, researchers found that insulin spending per patient per year rose significantly, from $231.48 in 2002 to $736.09 in 2013. The quantity of insulin per patient per year also rose, from 171 mL to 206 mL, but not to an extent that explained the rise in cost. The mean price per milliliter of insulin rose from $4.34 per mL to $12.92 per mL. The mean price of dipeptidyl peptidase-4 inhibitors also rose, but only by 34% (from $6.67 per pill in 2006 to $8.92 in 2013) compared to the 197% increase in insulin cost. Metformin prices decreased by 93% from 2002 to 2013. In 2013, estimated expenditure per patient was $228.20 for human insulin, $507.89 for analog insulin, and $502.57 for all other antihyperglycemics. The authors acknowledged increased treatment intensity contributed to the rise in spending on insulin, but concluded the results “suggest a need to reassess the effectiveness and cost-effectiveness of alternative antihyperglycemic therapies.”