FDA updates labeling for metformin use in patients with mild to moderate renal impairment

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Pharmacists can advise patients to speak with physicians about getting back on metformin if they were taken off it because of kidney function

FDA’s recent decision to update labeling information for metformin use in patients with mild to moderate renal impairment is welcome news for many health care providers, including pharmacists.

“What we have learned over the years is that metformin is generally safe for a much wider range of patients with diminished kidney function,” said Stuart Haines, PharmD, professor and vice chair for clinical services at University of Maryland School of Pharmacy. “The FDA relabeling opens up the therapy to a lot more patients.”

FDA said it received two Citizen Petition submissions requesting that the agency relax the current warnings.

“To address these Citizen Petitions, FDA conducted a detailed review of the available medical literature on the use of metformin in patients with renal impairment,” FDA said in an e-mail. This review led to the current regulatory action.

FDA also said it will change the unit of measure to determine kidney function from serum creatinine (SCr) to estimated glomerular filtration rate (eGFR)—a more accurate measure because it takes into account a patient’s age, gender, race, and/or weight as well as other factors.

“Strict serum creatinine cutoffs excluded a lot of patients who probably would have benefited from metformin,” said Haines. “But it also gave people a false sense of security. The dosing of metformin should be guided by an estimate of the patient’s renal function.”

Many physicians had already been prescribing metformin to patients with mild to moderate impairment in kidney function. Emily Prohaska, PharmD, BCACP, a clinical pharmacist at Balls Food Stores in Kansas, said this was the case with endocrinologists in her area. She said the updated labeling not only reassures her about legal liability but also will save her time by not having to call physicians’ offices to document that the prescriber was aware of the old SCr cutoffs.

Prohaska said pharmacists can advise patients during medication therapy management sessions to speak with their physicians about getting back on metformin if they were taken off of it because of kidney function. Many studies have supported use of metformin as a first-line therapy, including a recent one published in April in Annals of Internal Medicine. After analyzing more than 200 randomized, controlled or observational studies published through 2015, researchers concluded: “The evidence supports metformin as first-line therapy for type 2 diabetes, given its relative safety and beneficial effects on hemoglobin, A1C, weight, and cardiovascular mortality (compared with sulfonylureas).”

According to Haines, pharmacists can also remind patients to have their kidneys checked once a year and let them know that metformin does not hurt the kidneys; rather, it’s important to make sure patients have good kidney function because it’s the way the body eliminates metformin.

 

For more information, visit www.pharmacytoday.org for the upcoming June 2016 issue of Pharmacy Today.

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