Metformin Generic Name & Formulations
Metformin HCl 500mg, 850mg, 1000mg; tabs.
Adjunct to diet and exercise in type 2 diabetes.
Metformin Dosage and Administration
Take with meals. Individualize. ≥17yrs: Monotherapy: initially 500mg twice daily or 850mg once daily; may increase by increments of 500mg at 1-week intervals or 850mg in divided doses at 2-week intervals. Or, may increase from 500mg twice daily to 850mg twice daily after 2 weeks. Max 2.55g/day in 2–3 divided doses.
<10yrs: not established. Take with meals. Individualize. ≥10yrs: Monotherapy only: initially 500mg twice daily; may increase by 500mg increments at 1-week intervals. Max 2g/day in 2 divided doses.
Severe renal impairment (eGFR <30mL/min/1.73m2). Metabolic acidosis, diabetic ketoacidosis.
Metformin Boxed Warnings
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.
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.
Metformin Adverse Reactions
Diarrhea, nausea, vomiting, flatulence, asthenia, indigestion, abdominal discomfort, headache; rare: lactic acidosis (may be fatal).
Metformin Clinical Trials
Formerly known under the brand name Glucophage, Glucophage XR.
Metformin Patient Counseling