Fortamet, Glucophage, Glucophage XR, Glumetza, Riomet
Classifications: hormone & antidiabetic agent; biguanides; Therapeutic: antidiabetic; biguanide
Pregnancy Category: B
500 mg, 850 mg, 1000 mg tablets; 500 mg, 750 mg, 1000 mg sustained release tablets; 100 mg/mL oral solution
Biguanide oral hypoglycemic agent with a mechanism of action thought to be due to both increasing the binding of insulin
to its receptors and potentiating insulin action. Improves tissue sensitivity to insulin, increases glucose transport into
skeletal muscles and fat, and suppresses gluconeogenesis and hepatic production of glucose, thus lowering blood glucose
Effective in suppressing hepatic production of glucose as well as increasing the binding of insulin to its receptors in
Treatment of type 2 diabetes mellitus in patients not controlled with diet alone. May be used with an oral sulfonylurea.
Hypersensitivity to metformin; hepatic or cardiopulmonary insufficiency; alcoholism; concurrent infection; acute MI, cardiogenic
shock; diabetic ketoacidosis; hypoxemia, lactic acidosis; radiographic contrast administration; renal disease, renal failure,
renal impairment; sepsis; surgery; children <10 y.
Previous hypersensitivity to phenformin or buformin; anemia; coma; dehydration, diarrhea; older adults; ethanol intoxication;
fever; gastroparesis, GI obstruction; heart failure; hyperthyroidism, pituitary insufficiency; polycystic ovary syndrome;
trauma, emesis; pregnancy (category B), lactation.
Route & Dosage
|Type 2 Diabetes Mellitus
Adult: PO Start with 500 mg q.d. to t.i.d. or 850 mg q.d. to b.i.d. with meals, may increase by 500850 mg/d every 13 wk
(max: 2550 mg/d); or start with 500 mg sustained release with p.m. meal, may increase by 500 mg/d at p.m. meal qwk (max:
- Ensure that extended release tablets are not crushed or chewed. They must be swallowed whole.
- Use a calibrated oral syringe or container to measure the oral solution for accurate dosing.
- Give with or shortly after main meals.
- Withhold metformin 48 h before and 48 h after receiving IV contrast dye.
- Make dose increment, if needed, at 2- to 3-wk intervals.
- Store at 15°30° C (59°86° F).
Adverse Effects (≥1%)CNS:
Headache, dizziness, agitation, fatigue
Lactic acidosis. GI: Nausea, vomiting, abdominal pain, bitter or metallic taste, diarrhea, bloatedness, anorexia;
malabsorption of amino acids, vitamin B12
, and folic acid possible.
InteractionsDrug: Captopril, furosemide, nifedipine
may increase risk of hypoglycemia
reduces clearance of metformin. Concomitant therapy with azole antifungal agents (fluconazole, ketoconazole, itraconazole)
and oral hypoglycemic drugs
has been reported in severe hypoglycemia
. iodinated radiocontrast dyes
can cause lactic acidosis and acute kidney failure. Amiloride, cimetidine digoxin, dofetilide, midodrine, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim,
may decrease metformin elimination by competing for common renal
tubular transport systems. Acarbose
may decrease metformin levels. Iodinated contrast dyes
may cause lactic acidosis or acute kidney failure. Herbal: Garlic, ginseng, glucomannan
may increase hypoglycemic effects. Guar gum decreases absorption.
5060% of dose reaches systemic circulation. Peak:
13 h. Distribution:
Not bound to plasma proteins. Metabolism:
Not metabolized. Elimination:
In urine. Half-Life:
Assessment & Drug Effects
- Lab tests: Obtain baseline and periodic kidney and liver function tests; drug contraindicated in the presence of renal or
hepatic insufficiency. Monitor blood glucose and HbA1C, and lipid profile periodically.
- Monitor known or suspected alcoholics carefully for decreased liver function.
- Monitor cardiopulmonary status throughout course of therapy; cardiopulmonary insufficiency may predispose to lactic acidosis.
Patient & Family Education
- Be aware that hypoglycemia is not a risk when drug is taken in recommended therapeutic doses unless combined with other
drugs which lower blood glucose.
- Report to physician immediately S&S of infection, which increase the risk of lactic acidosis (e.g., abdominal pains, nausea,
and vomiting, anorexia).