Metformin Prescribing Trends in Patients With Diabetes, Chronic Kidney Disease

Results of a recent study suggest an increased metformin prescribing trend in patients with type 2 diabetes and chronic kidney disease (CKD) since 2010.

The findings were presented by Carlos Alvarez, PharmD, MSc, MSCS, associate professor at Texas Tech and University of Texas Southwestern, during a poster session on Friday, June 25, at the American Diabetes Association (ADA) Virtual 81st Scientific Sessions.¹

“Metformin is excreted unchanged in the urine and for years had a contraindication in this labeling in patients with SCr with [serum creatinine] cut-points of 1.5 in men and 1.4 in women,” Alvarez explained. “These cut-points were arbitrary and not really based on literature.”

In 2016, the FDA revised its guidance recommending the use of estimated glomerular filtration rate (eGFR) rather than SCr cut-points. The ADA also recommends the use of metformin as first-line therapy in patients with type 2 diabetes and CKD using these FDA constraints.

For the study, the investigators aimed to determine trends in incident metformin prescriptions for patients with type 2 diabetes and CKD from 2010 to 2018. Through drug utilization study, the investigators used administrative claims and electronic medical record data from the National Veterans Affairs (VA) Corporate Data Warehouse for 235,942 patients. Adult patients with type 2 diabetes and CKD as identified through validated algorithms using ICD-9/10 codes and laboratory values were included.

Patients who had a history of renal transplant or on chronic hemodialysis, or received metformin in the 2 years prior to cohort entry, and patients who received metformin in the 2 years prior to cohort entry were excluded. The study also excluded patients experiencing acute kidney injury at the time of cohort entry.

The investigators calculated metformin incidence rates using only new prescriptions after cohort entry. Metformin incidence was calculated for each CKD stage: 3a, 3b, 4, and 5.

“From 2010 to 2018, we did have a steady increase in the trend for metformin prescribing in patients with chronic kidney disease,” Alvarez said about the findings. This was statistically significant with a P<0.001 for trend.

There were similar results observed for stages 3a and 3b, where there was a statistically significant increasing trend for metformin prescribing per 1000 patients. However, “we did not see a statistically significant trend, or really any trend at all, for patients receiving metformin with CKD stages 4 or 5,” Alvarez added.

Overall, Alvarez reported an increase in metformin prescribing over time since 2010 for the whole CKD and type 2 diabetes cohort, which started to occur prior to the change in FDA policy.

Some limitations do occur, Alvarez noted. For example, the generalizability outside of the VA setting does come into question, although Alvarez indicated that the study did have a larger number of individuals in this particular cohort. Also, the ability for patients to obtain metformin from non-VA pharmacies could be another limitation; although rare, this can occur, Alvarez said.

“We need to determine additional things, like are there regional patterns for these trends and if certain provider types are more closely following FDA prescribing [policy],” Alvarez concluded. 

Reference

1. Alvarez CA, Perkins AR, Gregg LP, Mortensen EM. Trends in metformin prescribing in patients with chronic kidney disease after FDA label change. Presented at: American Diabetes Association Virtual 81st Scientific Sessions; June 25-29, 2021; online.