03:13am Sunday 08 December 2019

Outdated Warning on Antidiabetic Drug Curtails Its Use

There’s only one problem: An estimated 1 million Americans who are candidates for metformin aren’t taking it, according to new findings from researchers at Weill Cornell Medical College and the Perelman School of Medicine at the University of Pennsylvania.

Investigators have long believed that a decades-old safety warning issued by the U.S. Food and Drug Administration that advised doctors not to prescribe it to patients who have mild to moderate kidney disease was overly conservative, and that metformin is safer than the guidelines suggest. The study, published Jan. 5 in JAMA Internal Medicine, is the first to quantify the effect the safety warning has on patient care, and, the researchers say, underscores the need for the FDA to review the drug’s protocol.

“It’s a public health priority to relax these warnings,” said Dr. James Flory, a medical research fellow in endocrinology in the Department of Medicine who is collaborating with the Department of Healthcare Policy and Research at Weill Cornell. “It’s not like the warning label isn’t affecting practice. People are obeying it and ignoring this important drug that this population really needs.”

There are an estimated 25 million people with diabetes in the United States, and about one in three has some degree of kidney disease — a common byproduct of diabetes. The FDA discourages doctors from prescribing metformin to people who have mild to moderate kidney disease because of concerns that the drug could cause lactic acidosis, a potentially fatal condition when lactic acid builds up in the bloodstream faster than it can be removed. The agency based its safety recommendations on the experience of phenformin, a similar drug that was implicated in fatal cases of lactic acidosis and was eventually pulled off the market in the 1970s.

Since metformin was cautiously approved for use in the United States, diabetes researchers have investigated whether it carries the same risk for lactic acidosis as phenformin. They found that such cases are extremely rare, and suggest that metformin is safe for patients who have mild to moderate kidney disease. But the FDA has not updated its recommendations to reflect these findings.

“Once you issue a safety warning, it’s very hard to get it eliminated,” Dr. Flory said.

To quantify current usage, the investigators in the current study examined data from 2007-2011 reported in the National Health and Nutrition Examination Survey, which uses interviews and physical exams to assess the health and nutritional status of adults and children in the United States.

They looked at the drugs patients were prescribed, and identified patients who had diabetes severe enough that metformin would normally be recommended under current guidelines and appeared not to be taking it because of their kidney disease. They estimated that 1 million people could be benefitting from metformin if policies discouraging its use in mild to moderate kidney disease were revised.

Weill Cornell Medical College

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