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Metformin has been discovered for nearly 90 years. The advantages of safety, efficacy, and low price make it the most widely used oral hypoglycemic agent in clinical practice. In 2014, approximately 14.4 million people in the United States prescribed drugs containing metformin. As evidence of the benefits of metformin in more indications is constantly being disclosed, such as lowering blood lipids, anti-tumor, anti-aging, and even extending life expectancy, metformin has been crowned the “Magic Medicine.”

Metformin is currently approved for use in diet control and exercise for glycaemic control in patients with type 2 diabetes (T2DM), but since FDA approval was first approved in 1995, metformin drugs have been given a black box warning on the drug label. Patients with type 2 diabetes who have impaired renal function are strongly advised by the FDA to refrain from taking metformin-containing drugs so as not to cause excessive lactic acid accumulation in the blood and fatal lactic acidosis.

The risk of lactic acidosis in T2DM patients treated with metformin is related to their renal function levels and age. Although existing studies have shown that the probability of taking lactic acidosis with metformin is very low (30/1 million) and the probability of death from this is even lower (15/100 million cases), the FDA recommends that elderly people taking metformin should closely monitor renal function. Level. For patients with T2DM over 80 years of age, metformin should not be given unless the test proves that the kidney function is completely normal.

The FDA issued a drug safety newsletter on April 8 requesting the amendment of all drug labels containing metformin components to ease the use of metformin in some patients with renal insufficiency. Specific information is as follows:

After evaluating a large number of studies published in medical journals, we believe that metformin is safe enough for T2DM patients with mild renal impairment and some with moderate renal impairment. Therefore, we request amendments to the drug labeling of these drugs and hereby provide specific recommendations for the use of metformin in some T2DM patients with mild to moderate renal impairment.

We also recommend that the assessment of renal function in patients with T2DM should be based on the determination of metformin as the only measure of serum creatinine concentration, based on the glomerular filtration rate (eGFR).

The label revision mainly provides information on how and when renal function tests are performed in T2DM patients, including:

  • Before starting metformin, patients should be tested for eGFR.
  • Metformin is contraindicated in patients with eGFR <30 ml/min/1.73 m2.
  • Metformin is not recommended for patients with eGFR between 30 and 45/min/1.73m2.
  • All patients receiving metformin should be tested for eGFR once a year. In patients with a high risk of renal impairment (such as the elderly), the frequency of detecting eGFR should be more frequent.
  • For patients whose eGFR falls below 45/min/1.73m2 after receiving metformin treatment, the benefits and risks of continued metformin use should be assessed. If eGFR continues to fall below 30/min/1.73m2, metformin should be stopped.
  • Patients with an eGFR between 30 and 60/min/1.73m2, patients with a history of liver disease, alcohol abuse, and heart failure, and patients requiring arterial injection of iodine contrast agents should stop taking metformin before imaging with iodine contrast agents; After 48 hours of contrast imaging, eGFR should be tested again. After eGFR is stabilized, metformin can be continued.

Health care professionals should comply with the above recommendations when prescribing metformin in patients with T2DM who have renal impairment; if they have any questions about the use of metformin, they should communicate with health care providers in a timely manner.

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