Indications for: FORTAMET
Adjunct to diet and exercise in type 2 diabetes.
Swallow whole. Take with evening meal. Initially 500mg once daily; may increase by 500mg increments at 1-week intervals; max 2g once daily. If uncontrolled, consider trial of 1g twice daily.
<18yrs: not established.
Severe renal impairment (eGFR <30mL/min/1.73m2). Metabolic acidosis, diabetic ketoacidosis, with or without coma.
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 annually and Vit. B12 every 2–3yrs. Resumption of premenopausal ovulation in anovulatory patients may occur (may result in unintended pregnancy). 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; consider benefits/risks. 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; monitor. May need lower dose of concomitant sulfonylurea or insulin to reduce risk of hypoglycemia.
Diarrhea, nausea, vomiting, abdominal pain/distention, constipation, dyspepsia, flatulence, dizziness, headache, upper respiratory infection, taste disturbance; Vit. B12 deficiency; rare: lactic acidosis (may be fatal).