Metformin Dosage

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Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Diabetes Type 2

Immediate-release:
Initial dose: 500 mg orally twice a day or 850 mg orally once a day
Dose titration: Increase in 500 mg weekly increments or 850 mg every 2 weeks as tolerated
Maintenance dose: 2000 mg daily
Maximum dose: 2550 mg daily

Comments: Take in divided doses 2 to 3 times a day with meals. Titrate slowly to minimize gastrointestinal side effects. In general, significant responses are not observed with doses less than 1500 mg/day.

Extended-release:
Initial dose: 500 to 1000 mg orally once a day
Dose titration: Increase in 500 mg weekly increments as tolerated
Maintenance dose: 2000 mg daily
Maximum dose: 2500 mg daily

Comments: If glycemic control is not achieved with once a day administration of an extended-release product, consider dividing doses. If higher doses are required, may switch to immediate-release product.

Use: To improve glycemic control in adults with type 2 diabetes mellitus as an adjunct to diet and exercise.

Usual Pediatric Dose for Diabetes Type 2

10 years or older:
Immediate-release:
Initial dose: 500 mg orally twice a day
Dose titration: Increase in 500 mg weekly increments as tolerated
Maintenance dose: 2000 mg daily
Maximum dose: 2000 mg daily

Comments: Take in divided doses 2 to 3 times a day with meals. Titrate slowly to minimize gastrointestinal side effects.

Safety and effectiveness of metformin extended-release has not been established in pediatric patients less than 18 years of age.

Use: To improve glycemic control in children with type 2 diabetes mellitus as an adjunct to diet and exercise.

Renal Dose Adjustments

Renal impairment (serum creatinine 1.5 mg/dL or greater in men, 1.4 mg/dL or greater in women, or abnormal CrCl): Use is contraindicated

Liver Dose Adjustments

Not recommended in patients with liver impairment.

Dose Adjustments

-Elderly, debilitated, and malnourished patients: Titration to the maximum dose is generally not recommended.

-Concomitant Insulin therapy: When initiating treatment in patients currently receiving insulin, metformin should be started at 500 mg orally once a day and titrated in 500 mg increments weekly. When fasting blood glucose levels decrease to less than 120 mg/dL, consider decreasing the insulin dose by 10% to 25%.

Therapeutic drug monitoring/range: Steady-state plasma concentrations are achieved within 24 to 48 hours and are generally less than 1 mcg/mL. Metformin levels greater than 5 mcg/mL have been implicated as the cause of lactic acidosis.

Precautions

US BOXED WARNING: Lactic Acidosis
-Lactic acidosis is a rare, but serious complication that may occur due to metformin accumulation.
-Increased risk is associated with renal impairment, sepsis, dehydration, excess alcohol intake, hepatic impairment, and acute congestive heart failure.
-Onset is often subtle, accompanied by nonspecific symptoms such as malaise, myalgia, respiratory distress, increasing somnolence, and nonspecific gastrointestinal distress.
-Laboratory abnormalities include low pH, increased anion gap, and elevated blood lactate.
-If acidosis is suspected, immediately discontinue drug and hospitalize patient.

Safety and efficacy have not been established in patients younger than 10 years.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available.

Other Comments

Administration advice:
-Take with meals
-Gastrointestinal tolerability may be improved by a slow increase in dosage.
-Extended-release product: Take with evening meal; swallow whole; do not crush, cut, dissolve, or chew

General:
-Not for use in patients with type 1 diabetes or diabetic ketoacidosis.
-Temporarily stop treatment prior to radiologic studies utilizing iodinated contrast materials and for surgical procedures when restricted food or fluid intake is expected; may resume once adequate renal function is confirmed.

Monitoring:
Renal: Assess renal function baseline, repeat at least annually and more often as clinically indicated.
Hematologic: Measure hematologic parameters annually
-Monitor glycemic control

Patient advice:
-Tablet shells may appear in feces, and this should not cause alarm.
-Inform patients about the risk of lactic acidosis, conditions that might predispose them to its occurrence, and symptoms to watch for and report.
-Advise patient that this drug will need to be temporarily stopped if undergoing radiologic studies with intravascular iodinated contrast materials or surgical procedures that will limit food or fluid intake.
-Advise patients on the risks of excessive alcohol intake.
-Tell patients that while gastrointestinal symptoms might be common when initiating treatment, gastrointestinal problems after initiation should be reported.

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