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Metformin is an oral drug indicated to treat Type 2 diabetes. In March 2020, the online pharmacy Valisure petitioned the U.S. Food & Drug Administration (FDA) for a metformin recall after tests indicated some tablets contained unacceptable levels of N-Nitrosodimethylamine (NDMA) – a probable human carcinogen.

About Metformin

Metformin is the preferred first-line treatment for adults or children over the age of 10 who suffer from Type 2 diabetes. The medication is also approved for:

  • Treatment of gestational diabetes.
  • Management of antipsychotic-induced weight gain.
  • Type 2 diabetes prevention.
  • Treatment and prevention of polycystic ovary syndrome (PCOS).

Currently, metformin is the only drug recommended by the American Diabetes Association for pre-diabetes. Researchers are also studying metformin for its possible antiaging, anticancer, and neuroprotective effects.

Metformin is used in conjunction with diet and exercise. It may also be taken with insulin and in combination with other diabetes drugs.

Metformin is NOT approved to treat Type 1 diabetes.

Unlike another class of oral diabetes drugs call sulfonylureas, metformin does not stimulate insulin release, but primarily reduces the release of glucose from the liver.

Metformin History

Metformin is derived from a plant called Galega officinalis, which in medieval times was used to relieve frequent urination that was likely a symptom of the disease now known as Type 2 diabetes.

By the late 19th century, scientist knew that two active ingredients in Galega officinalis — galegine or isoamylene guanidine – could lower blood sugar levels. But guanidine was found to be too toxic for clinical use. The precise structure of galegine – the less toxic extract – was confirmed in 1923.

In 1957, metformin was shown to lower blood glucose in patients with Type 2 diabetes, although not in healthy individuals. The drug became available in the British National Formulary in 1958, and was cleared for use in Canada in 1972.

The FDA finally approved metformin in 1994, after studies suggested it not only controlled blood glucose levels in Type 2 diabetics, but also decreased their risk of heart attack and death from all cause.  Bristol-Myers Squibb launched Glucophage, the first branded formulation of metformin sold in the United States, the following year.

Today, metformin is marketed under several brand names, including:

  • Fortamet
  • Glucophage
  • Glucophage XR
  • Glumetza
  • Riomet

Various generic drug makers are also licensed to sell metformin in the United States, including Actavis Pharma, Inc., Amneal Pharmaceuticals LLC, and Heritage Pharmaceuticals Inc., among others.

Metformin Side Effects

Before taking metformin, patients should tell their doctor if they ever had:

  • Kidney disease (kidney function may need to be checked prior to treatment.)
  • High ketone levels in the blood or urine.
  • Heart disease
  • Congestive heart failure
  • Liver disease
  • If they also use insulin or other oral diabetes medications.

In very rare instances, metformin can cause lactic acidosis, a dangerous and potentially life-threatening build-up of lactic acid in the blood. For this reason, patients taking metformin should seek emergency medical attention if they experience:

  • Unusual muscle pain
  • Trouble breathing
  • Stomach pain
  • Dizziness
  • Feeling cold
  • Feeling very weak or tired

Metformin patients should also seek emergency medical help if they experience signs of an allergic reaction, including:  hives; difficult breathing; swelling of the face, lips, tongue, or throat.

The most common metformin side effects include:

  • Low blood sugar
  • Nausea/upset stomach
  • Diarrhea

Valisure Tests Detect High Levels of NDMA in Some Metformin Products

In December 2018, the FDA announced it was investigating the possibility that some metformin products contained high levels of NDMA, a contaminant that has been linked to an increased risk of cancer, especially liver, kidney, and pancreatic cancer. While the agency later acknowledged that metformin samples had tested positive for the chemical, the public was assured that the levels detected were well below the acceptable daily intake limit of 96 nanograms.

But in March 2020, Valisure – the online pharmacy that had found NDMA in Zantac – petitioned the FDA for a metformin recall, after its own investigation found NDMA in 16 of 38 samples it tested. The highest levels were found in Amneal Pharmaceutical’s metformin, which in some cases contained as much as 16-times the FDA’s recommended daily limits. Several companies’ metformin contained more than 10 times the limit.

“The presence of this carcinogen in metformin where multiple tablets can be taken daily and often for a lifetime diabetic condition, makes this finding particularly concerning,” Deanna Akinbajo, PharmD, MPH, Chief Pharmacist of Valisure, said in a statement announcing the findings. “Furthermore, the increased prevalence of diabetes in adolescents and young adults strongly underscores the need for quick action to protect patients.”

The FDA indicated it was evaluating Valisure’s petition, but as of this time, has not ordered any metformin recalls.

  1. MedlinePlus (2019) “Metformin”
  2. Diabetes Forecast (2010) “The Origins of Metformin”
  3. NCBI (2020) “Metformin”
  4. FDA (2019) “Statement from Janet Woodcock, M.D., director of FDA’s Center for Drug Evaluation and Research, on impurities found in diabetes drugs outside the U.S.”
  5. FDA (2020) “FDA Updates and Press Announcements on NDMA in Metformin”
  6. Valisure (2020) “Valisure Detects High Levels of NDMA in Metformin”
  7. Valisure (2020) “Valisure Citizen Petition on Metformin”
Last Modified: July 13, 2020

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