Indications for: Metformin Ext-Rel

Adjunct to diet and exercise in type 2 diabetes.

Adult Dosage:

Swallow whole. Take with evening meal. Individualize. ≥17yrs: initially 500mg once daily; may increase by 500mg increments at 1-week intervals; max 2g once daily or in 2 divided doses. If higher doses needed, switch to immediate-release form at max 2.55g/day in divided doses.

Children Dosage:

<17yrs: not established. Use immediate-release form.

Metformin Ext-Rel Contraindications:

Severe renal impairment (eGFR <30mL/min/1.73m2). Metabolic acidosis, diabetic ketoacidosis.

Boxed Warning:

Lactic acidosis.

Metformin Ext-Rel Warnings/Precautions:

Increased risk of metformin-associated lactic acidosis in renal or hepatic impairment, concomitant use of certain drugs (eg, carbonic anhydrase inhibitors), ≥65yrs of age, undergoing radiological contrast study, surgery and other procedures, hypoxic states, and excessive alcohol intake; discontinue if lactic acidosis occurs. Discontinue at time of, or prior to intravascular iodinated contrast imaging in patients with eGFR 30–60mL/min/1.73m2, history of hepatic impairment, alcoholism, heart failure, or will be given intra-arterial contrast; reevaluate eGFR 48hrs after procedure and restart therapy if renally stable. Suspend therapy if dehydration occurs or before surgery. Avoid if evidence of hepatic disease. Assess renal function prior to starting and periodically thereafter; more frequently in elderly or patients whose eGFR falls <45mL/min/1.73m2; see full labeling. Monitor hematology (esp. serum Vit. B12 in susceptible patients). Pregnancy. Nursing mothers.

See Also:

Metformin Ext-Rel Classification:


Metformin Ext-Rel Interactions:

Increased risk of lactic acidosis with topiramate, other carbonic anhydrase inhibitors (eg, zonisamide, acetazolamide, dichlorphenamide); monitor. Concomitant cationic drugs that interfere with renal tubular transport systems (eg, ranolazine, vandetanib, dolutegravir, cimetidine) may increase metformin levels; monitor. Avoid excessive alcohol intake (potentiates effects of metformin on lactate). Diuretics, steroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, sympathomimetics, calcium channel blockers, isoniazid, nicotinic acid, others may cause hyperglycemia. May need lower dose of concomitant insulin and/or insulin secretagogue (eg, sulfonylurea) to reduce risk of hypoglycemia.

Adverse Reactions:

Diarrhea, nausea, vomiting, flatulence, asthenia, indigestion, abdominal discomfort, headache; rare: lactic acidosis (may be fatal).


Formerly known under the brand name Glucophage, Glucophage XR.

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