metformin (Rx)

Brand and Other Names:Glucophage, Glucophage XR, more...Fortamet, Glumetza, Riomet
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Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

tablet, immediate-release

  • 500mg
  • 850mg
  • 1000mg

tablet, extended-release

  • 500mg
  • 750mg
  • 1000mg

oral solution

  • 100mg/mL
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Type 2 Diabetes Mellitus

Monotherapy or with sulfonylurea

Immediate-release tablet or solution

  • Initial: 500 mg PO q12hr or 850 mg PO qDay with meals; increase q2Weeks
  • Maintenance: 1500-2550 mg/day PO divided q8-12hr with meal
  • Not to exceed 2550 mg/day

Extended-release

  • Glucophage XR: 500 mg PO qDay with dinner; titrate by 500 mg/day qWeek; not to exceed 2000 mg/day
  • Fortamet: 500-1000 mg PO qDay; titrate by 500 mg/day qWeek; not to exceed 2500 mg/day
  • Glumetza: 1000 mg PO qDay; titrate by 500 mg/day qWeek; not to exceed 2000 mg/day

Type 2 Diabetes Prevention (Off-label)

850 mg PO qDay

Target dosing: 850 mg PO q12hr

Dosage Modifications

Hepatic impairment: Avoid use; risk of lactic acidosis

Renal impairment

  • Obtain eGFR before starting metformin
  • eGFR <30 mL/min/1.73 m²: Contraindicated
  • eGFR 30-45 mL/min/1.73 m²: Not recommended to initiate treatment
  • Monitor eGFR at least annually or more often for those at risk for renal impairment (eg, elderly)
  • If eGFR falls below 45mL/min/1.73 m² while taking metformin, risks and benefits of continuing therapy should be evaluated
  • If eGFR falls below 30 mL/min/1.73 m²: while taking metformin, discontinue the drug

Polycystic Ovary Syndrome (Orphan)

Orphan designation for treatment of pediatric polycystic ovary syndrome

Sponsor

  • EffRx Pharmaceuticals SA; Wolleraustrass 41 B; 8807 Freienbach (SZ); SWITZERLAND

Dosage Forms & Strengths

tablet, immediate-release

  • 500mg
  • 850mg
  • 1000mg

tablet, extended-release

  • 500mg
  • 750mg
  • 1000mg

oral solution

  • 100mg/mL
more...

Type 2 Diabetes Mellitus

Immediate-release (10-16 years)

  • Initial: 500 mg PO q12hr
  • Maintenance: Titrate qWeek by 500 mg; no more than 2000 mg/day in divided doses

Immediate-release (≥17 years)

  • Initial: 500 mg PO q12hr or 850 mg PO qDay with meals; increase q2Weeks
  • Maintenance: 1500-2550 mg/day PO divided q8-12hr with meal
  • No more than 2550 mg/day

Extended-release (<17 years)

  • Safety and efficacy not established

Extended-release (≥17 years)

  • Glucophage XR: 500 mg PO qDay with dinner; titrate by 500 mg/day qWeek; not to exceed 2000 mg/day
  • Fortamet: 500-1000 mg PO qDay; titrate by 500 mg/day qWeek; not to exceed 2500 mg/day

Dosage Modifications

Renal impairment

  • Obtain eGFR before initiating metformin
  • eGFR <30 mL/min/1.73 m²: Contraindicated
  • eGFR 30-45 mL/min/1.73 m²: 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 (eg, elderly)
  • If eGFR falls to <45 mL/min/1.73 m² during treatment: Assess the benefits and risks of continuing treatment
  • If eGFR falls to <30 mL/min/1.73 m² during treatment: Discontinue

Elderly patients are more likely to have decreased renal function; 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 >80 years unless normal renal function establishedInitial 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 metformin did not include sufficient numbers of elderly patients to determine whether they respond differently from younger patients

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Interactions

Interaction Checker

and metformin

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     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            Frequency Not Defined

            Asthenia

            Diarrhea

            Flatulence

            Weakness

            Myalgia

            Upper respiratory tract infection

            Hypoglycemia

            GI complaints

            Lactic acidosis (rare)

            Low serum vitamin B-12

            Nausea/vomiting

            Chest discomfort

            Chills

            Dizziness

            Abdominal distention

            Constipation

            Heartburn

            Dyspepsia

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            Warnings

            Black Box Warnings

            Lactic acidosis is a rare, but potentially severe, consequence of therapy with metformin; it is characterized by elevated blood lactate levels (>5 mmol/L), decreased blood pH, electrolyte disturbances with an increased anion gap, and an increased lactate/pyruvate ratio; when metformin is implicated as the cause of lactic acidosis, metformin plasma concentrations >5 mcg/mL are generally found

            Risk factors for metformin-associated lactic acidosis include renal impairment, concomitant use of certain drugs (eg, carbonic anhydrase inhibitors such as topiramate), age 65 years old or greater, having a radiological study with contrast, surgery and other procedures, hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, and hepatic impairment; if metformin-associated lactic acidosis is suspected, immediately discontinue

            Patients with CHF requiring pharmacologic management, in particular those with unstable or acute CHF who are at risk for hypoperfusion and hypoxemia, are at an increased risk for lactic acidosis; the risk for lactic acidosis increases with the degree of renal dysfunction and the patient’s age

            Do not start in patients aged 80 years or older unless CrCl demonstrates that renal function is not reduced, because these patients are more susceptible to developing lactic acidosis; metformin should be promptly withheld in the presence of any condition associated with hypoxemia, dehydration, or sepsis

            Should generally be avoided in patients with clinical or laboratory evidence of hepatic disease; patients should be cautioned against excessive alcohol intake, either acute or chronic, during metformin therapy because alcohol potentiates the effects of metformin on lactate metabolism

            Discontinue metformin at the time of or before an iodinated contrast imaging procedure in patients with an eGFR between 30-60 mL/minute/1.73 m²; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinate contrast

            The onset of lactic acidosis often is subtle and accompanied by nonspecific symptoms (eg, malaise, myalgias, respiratory distress, increasing somnolence, nonspecific abdominal distress); with marked acidosis, hypothermia, hypotension, and resistant bradyarrhythmias may occur; patients should be instructed regarding recognition of these symptoms and told to notify their physician immediately if the symptoms occur; metformin should be withdrawn until the situation is clarified; serum electrolytes, ketones, blood glucose, and, if indicated, blood pH, lactate levels, and even blood metformin levels may be useful

            Once a patient is stabilized on any dose level of metformin, GI symptoms, which are common during initiation of therapy, are unlikely to be drug related; later occurrences of GI symptoms could be due to lactic acidosis or other serious disease

            Lactic acidosis should be suspected in any diabetic patient with metabolic acidosis who is lacking evidence of ketoacidosis (ketonuria and ketonemia); lactic acidosis is a medical emergency that must be treated in a hospital setting; in a patient with lactic acidosis who is taking metformin, the drug should be discontinued immediately and general supportive care measures promptly instituted; metformin is highly dialyzable (clearance up to 170 mL/min under good hemodynamic conditions); prompt hemodialysis is recommended to correct the acidosis and to remove the accumulated metformin; such management often results in prompt reversal of symptoms and recovery

            Contraindications

            Hypersensitivity to metformin

            CHF

            Diabetic ketoacidosis with or without coma

            Severe renal disease: eGFR <30 mL/min/1.73 m²

            Abnormal creatinine clearance resulting from shock, septicemia, or myocardial infarction

            Lactation

            Cautions

            Increased risk of severe hypoglycemia especially in elderly, debilitated or malnourished, adrenal or pituitary insufficiency, dehydration, heavy alcohol use, hypoxic states, hepatic/renal impairment, stress due to infection, fever, trauma, or surgery

            Withholding of food and fluids during surgical or other procedures may increase risk for volume depletion, hypotension, and renal impairment; therapy should be temporarily discontinued while patients have restricted food and fluid intake

            Rare lactic acidosis may occur due to metformin accumulation; fatal in approximately 50% of cases; risk increases with age, degree of renal dysfunction, and with unstable or acute CHF; if metformin-associated lactic acidosis suspected, general supportive measures should be instituted promptly in a hospital setting, along with immediate discontinuation of therapy; in patients with a diagnosis or strong suspicion of lactic acidosis, prompt hemodialysis is recommended to correct acidosis and remove accumulated metformin (metformin hydrochloride is dialyzable, with a clearance of up to170 mL/minute under good hemodynamic conditions); hemodialysis has often resulted in reversal of symptoms and recovery

            Possible increased risk of CV mortality

            May cause ovulation in anovulatory and premenopausal PCOS patients

            May be necessary to discontinue therapy with metformin and administer insulin if patient is exposed to stress (fever, trauma, infection), or experiences diabetic ketoacidosis

            Several of the postmarketing cases of metformin-associated lactic acidosis occurred in setting of acute congestive heart failure (particularly when accompanied by hypoperfusion and hypoxemia); cardiovascular collapse (shock) acute myocardial infarction, sepsis, and other conditions associated with hypoxemia have been associated with lactic acidosis and may also cause prerenal azotemia; discontinue therapy when such events occur

            May impair vitamin B12 or calcium intake/absorption; monitor B12 serum concentrations periodically with long-term therapy

            Not indicated for use in patients with type 1 diabetes mellitus that are insulin dependent due to lack of efficacy

            Withhold in patients with dehydration and/or prerenal azotemia

            Clinical recommendations based upon the patient’s renal function

            • Before initiating therapy, obtain an eGFR
            • Initiation of therapy is not recommended in patients with eGFR between 30 –45 mL/minute/1.73 m²
            • Obtain an eGFR at least annually in all patients receiving therapy
            • In patients at increased risk for development of renal impairment (e.g., the elderly), renal function should be assessed more frequently
            • If eGFR later falls below 45 mL/minute/1.73 m², assess benefit and risk of continuing therapy

            Iodinated contrast imaging procedures

            • Discontinue metformin at the time of or before an iodinated contrast imaging procedure in patients with an eGFR between 30-60 mL/minute/1.73 m²; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinate contrast
            • Reevaluate eGFR 48 hr after the imaging procedure; restart metformin if renal function is stable
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            Pregnancy & Lactation

            Pregnancy category: B

            Lactation: Enters breast milk; not recommended

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Decreases hepatic glucose production; decreases GI glucose absorption; increases target cell insulin sensitivity

            Absorption

            Bioavailability: 50-60%

            Peak plasma time

            • Regular-release: 2-3 hr
            • Extended-release: 4-8 hr

            Distribution

            Protein bound: Minimal

            Vd: 650 L (regular-release)

            Metabolism

            Metabolism: Not by liver

            Elimination

            Half-Life: 4-9 hr

            Dialyzable: Yes (hemodialysis)

            Renal clearance: 450-540 mL/min (regular-release)

            Excretion: Urine (90%, by tubular secretion)

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            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

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            • View the formulary and any restrictions for each plan.
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            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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