Generic Name and Formulations:
Metformin HCl 500mg, 1000mg; ext-rel tabs.
Indications for FORTAMET:
Adjunct to diet and exercise in type 2 diabetes.
Swallow whole. Take with evening meal. Individualize. ≥17yrs: Monotherapy: initially 1000mg once daily; may increase by 500mg increments at 1-week intervals; max 2.5g once daily. Adding to insulin: initially 500mg once daily; may increase by 500mg increments at 1-week intervals; max 2.5g once daily. Reduce insulin dose by 10–25% as needed. Concomitant sulfonylureas: see full labeling.
<17yrs: not recommended.
Severe renal impairment (eGFR <30mL/min/1.73m2). Metabolic acidosis, diabetic ketoacidosis.
Increased risk of metformin-associated lactic acidosis in renal or hepatic impairment, concomitant use of certain drugs (eg, cationic drugs), ≥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 clinical or lab evidence of hepatic disease. Assess renal function prior to starting and periodically thereafter; more frequently in elderly or if eGFR <60mL/min/1.73m2. Elderly, debilitated, uncompensated strenuous exercise, malnourished or deficient caloric intake, adrenal or pituitary insufficiency, or alcohol intoxication: increased risk of hypoglycemia. Monitor hematology (esp. serum Vit. B12 in susceptible patients). Pregnancy (Cat.B), nursing mothers: not recommended; consider using insulin instead.
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 sulfonylurea or insulin to reduce risk of hypoglycemia. β-blockers may mask hypoglycemia. May affect or be affected by furosemide, nifedipine.
Diarrhea, nausea, dyspepsia, flatulence, abdominal pain; rare: lactic acidosis (may be fatal).