Dosing & Uses
Dosage Forms & Strengths
tablet, immediate-release
- 500mg
- 850mg
- 1000mg
tablet, extended-release
- 500mg
- 750mg
- 1000mg
oral solution
- 100mg/mL
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
Myoclonus Epilepsy (Orphan)
Orphan designation for treatment of progressive myoclonus epilepsy type 2 (Lafora disease)
Sponsor
- Consorcio Centro de Investigación Biomédica en Red, M.P. (CIBER); Monforte de Lemos, 3-5 Pabellon 11; Madrid, Spain
Dosage Forms & Strengths
tablet, immediate-release
- 500mg
- 850mg
- 1000mg
tablet, extended-release
- 500mg
- 750mg
- 1000mg
oral solution
- 100mg/mL
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
Interactions
Interaction Checker
No Results
Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor
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
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
Concomitant administration of insulin and insulin secretagogues (e.g., sulfonylurea) may increase risk of hypoglycemia; therefore, a lower dose of insulin or insulin secretagogue may be required to minimize risk of hypoglycemia when used in combination with metformin
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
Conclusive evidence of macrovascular risk reduction with metformin not established
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
Pregnancy & Lactation
Pregnancy
Limited data with in pregnant women are not sufficient to determine drug-associated risk for major birth defects or miscarriage; published studies with metformin use during pregnancy have not reported a clear association with metformin and major birth defect or miscarriage risk; poorly-controlled diabetes mellitus in pregnancy increases maternal risk for diabetic ketoacidosis, pre-eclampsia, spontaneous abortions, preterm delivery, stillbirth and delivery complications; poorly controlled diabetes mellitus increases the fetal risk for major birth defects, stillbirth, and macrosomia related morbidity
Human data
- Published data from post-marketing studies have not reported clear association with metformin and major birth defects, miscarriage, or adverse maternal or fetal outcomes when used during pregnancy; however, these studies cannot definitely establish absence of any metformin-associated risk because of methodological limitations, including small sample size and inconsistent comparator groups
Animal data
- Metformin hydrochloride did not adversely affect development outcomes when administered to pregnant rats and rabbits at doses up to 600 mg/kg/day; this represents exposure of about 2 and 5 times a 2550 mg clinical dose based on body surface area comparisons for rats and rabbits, respectively; determination of fetal concentrations demonstrated a partial placental barrier to metformin
Reproduction potential
- Discuss potential for unintended pregnancy with premenopausal women as therapy may result in ovulation in some anovulatory women
Lactation
Limited published studies report that metformin is present in human milk; however, there is insufficient information to determine effects of metformin on breastfed infant and no available information on effects of metformin on milk production; therefore, developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for therapy and any potential adverse effects on breastfed child from therapy or from the underlying maternal condition
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.
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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Patient Handout
Formulary
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