Metformin

DEA Class; Rx

Common Brand Names; Glucophage, Glucophage XR, Glumetza, Riomet, Riomet ER

Adjunctive therapy to diet and exercise to improve glycemic control in adults with type 2 diabetes

Monotherapy or with sulfonylurea

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

• Diarrhea, immediate-release product (53%)
• Nausea/vomiting, immediate-release product (25%)
• Diarrhea, extended-release product (10%)
• Nausea/vomiting, extended-release product (7%)
• Low serum vitamin B-12 (7%)
• Abdominal pain (1-5%)
• Constipation (1-5%)
• Abdomen distention (1-5%)
• Dyspepsia/heartburn (1-5%)
• Flatulence (1-5%)
• Dizziness (1-5%)
• Headache (1-5%)
• Upper respiratory infection (1-5%)
• Taste disturbance (1-5%)
• Postmarketing Reports H3
• Cholestatic, hepatocellular, and mixed hepatocellular liver injury
• Lactic acidosis
• Hypoglycemia

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

Limited data with in pregnant women are not sufficient to determine drug-associated risk for major birth defects or miscarriage

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

Metformin hydrochloride

tablet, immediate-release

• 500mg (generic)
• 850mg (generic)
• 1000mg (generic)

tablet, extended-release

• 500mg (generic, Glumetza)
• 750mg (generic)

1000mg (generic, Glumetza)

oral solution

• 100mg/mL (Riomet)

oral suspension, extended-release

• 47.31g/473mL per bottle (Riomet ER)
• Reconstituted suspension is 500mg/5mL