April 27, 2017
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Metformin

Medical and Pharmacy Editor:

Brand Name: Glucophage, Glucophage XR, Fortamet, Glumetza, Riomet

Generic Name: metformin

Drug Class: Anti-diabetics (medications to treat or manage diabetes), Biguanides

What Is Metformin and How Does It Work?

Metformin is a drug approved by the U.S. Food and Drug Administration as a prescription medication to treat diabetes. This medication is used to decrease hepatic (liver) glucose production, to decrease GI glucose absorption and to increase target cell insulin sensitivity. This medication is a treatment indicated as an adjunct to diet, exercise, and lifestyle changes such as weight loss to improve glycemic (blood sugar) control in adults with type 2 diabetes. Many patients with type 2 diabetes will eventually need to take insulin by injection. Metformin does not cause weight gain.

About Type 2 Diabetes

Type 2 diabetes (also known as adult-onset or non-insulin-dependent diabetes) is the most common form of diabetes. Type 2 diabetes is a condition in which the body does not process insulin properly, resulting in elevated blood sugar (blood glucose). Insulin is a hormone that is produced in the pancreas. Type 2 diabetes is diagnosed more often in people who are overweight or obese, and who are not physically active. Patients with diabetes should also note that a healthy weight improves cholesterol levels and overall health. Insulin resistance is a condition that is commonly seen in type 2 diabetes, where it becomes difficult for the body to use the insulin that is produced. Certain genes that affect insulin production rather than insulin resistance are a risk factor for developing type 2 diabetes. Family history of diabetes is a risk factor, and people of certain races or ethnicities are at higher risk. Abnormal glucose production by the liver can also lead to elevated blood sugar (glucose) levels.

Metformin is available under the following different brand names: Glucophage, Glucophage XR, Fortamet, Glumetza, and Riomet.

Dosages of Metformin Should Be Given As Follows:

Adult Dosage Forms & Strengths for Diabetes

Tablet, immediate-release

  • 500 mg
  • 850 mg
  • 1000 mg

Extended-release tablet

  • 500 mg
  • 750 mg
  • 1000 mg

Oral solution

  • 500 mg
  • 750 mg
  • 1000 mg

Pediatric Dosage Forms & Strengths for Diabetes

Tablet, immediate-release

  • 500 mg
  • 850 mg
  • 1000 mg

Extended-release Tablet

  • 500 mg
  • 750 mg
  • 1000 mg

Oral solution

  • 500 mg
  • 750 mg
  • 100 mg

Dosage Considerations

For Adults with Type 2 Diabetes Mellitus

Monotherapy or with sulfonylurea

Immediate-release tablet or solution
  • Initial dose: 500 mg orally every 12 hours or 850 mg orally once/day with meals; increase every two weeks
  • Maintenance doses: 1500-2550 mg/day taken orally divided once every 8-12hr with meal
  • Not to exceed 2550 mg/day
Extended-release
  • Glucophage XR: 500 mg orally once/day with dinner; titrate by 500 mg/day each week; not to exceed 2000 mg/day
  • Fortamet: 500-1000 mg orally once/day; titrate by 500 mg/day each week; not to exceed 2500 mg/day
  • Glumetza: 1000 mg orally once/day; titrate by 500 mg/day each week; not to exceed 2000 mg/day

For Prevention of Type 2 Diabetes

  • 850 mg by mouth every day
  • Target dosing: 850 mg orally every 12 hours

Dosage Modifications

Hepatic (liver) impairment: Avoid use; risk of lactic acidosis.

Renal (kidney) impairment

  • Obtain eGFR before starting metformin
  • eGFR less than 30 mL/min/1.73 mē: Contraindicated
  • eGFR 30-45 mL/min/1.73 mē: Not recommended to initiate treatment
  • Monitor eGFR at least annually or more often for those at risk for renal impairment (e.g., elderly)
  • If eGFR falls below 45mL/min/1.73 mē while taking metformin, health risks and benefits of continuing therapy should be evaluated
  • If eGFR falls below 30 mL/min/1.73 mē: while taking metformin, discontinue the drug

Polycystic Ovary Syndrome (Orphan)

Orphan designation for treatment of pediatric polycystic ovary syndrome

Pediatric Dosage Considerations

Type 2 Diabetes Mellitus

Immediate-release (10-16 years)

    Initial: 500 mg orally every 12 hours

    Maintenance: Titrate once/week by 500 mg; no more than 2000 mg/day in divided doses

Immediate-release (17 years of age and older)
  • Initial dose: 500 mg orally every 12 hours or 850 mg orally once/daily with meals; increase every two weeks
  • Maintenance doses: 1500-2550 mg/day orally divided once every 8-12hr with meal
  • No more than 2550 mg/day
Extended-release (under 17 years of age)
  • Safety and efficacy not established
Extended-release (17 years of age and older)
  • Glucophage XR: 500 mg orally once/daily with dinner; titrate by 500 mg/day once each week; not to exceed 2000 mg/day
  • Fortamet: 500-1000 mg orally once/daily; titrate by 500 mg/day once each week; not to exceed 2500 mg/day

Dosage Modifications of Medication

Renal impairment (Poor kidney function)

  • Obtain eGFR before initiating metformin
  • eGFR less than 30 mL/min/1.73 mē: Contraindicated
  • eGFR 30-45 mL/min/1.73 mē: Initiating not recommended
  • Obtain GFR at least annually in all patients taking metformin; assess eGFR more frequently in patients at increased risk for renal impairment (e.g., elderly)
  • If eGFR falls to less than 45 mL/min/1.73 mē during treatment: Assess the benefits and risks of continuing treatment
  • If eGFR falls to less than 30 mL/min/1.73 mē during treatment: Discontinue

Geriatric Dosage

Elderly patients with diabetes are more likely to have decreased renal function with the use of this drug; contraindicated in patients with renal impairment, carefully monitor renal function in the elderly and use with caution as age increases.

Not for use in patients over 80 years unless normal renal function established initial and maintenance dosing of metformin should be conservative in patients with advanced age due to the potential for decreased renal function in this population.

Controlled clinical studies of this drug did not include sufficient numbers of elderly patients with diabetes to determine whether they respond differently from younger patients with diabetes.

Medically Reviewed by a Doctor on 4/14/2017



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