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metformin hydrochloride
Glucophage

Pregnancy Risk Category B

How supplied
Tablets:
500 mg, 850 mg

Action
Decreases hepatic glucose production and intestinal absorption of glucose and improves insulin sensitivity (increases peripheral glucose uptake and utilization).

Indications & dosage
Adjunct to diet to lower blood glucose level in patients with type 2 non-insulin-dependent diabetes mellitus--

Adults:
initially, 500 mg P.O. b.i.d. given with morning and evening meals, or 850 mg P.O. once daily given with morning meal. When 500-mg form used, dosage increased 500 mg weekly to maximum dose of 2,500 mg P.O. daily in divided doses, p.r.n. When 850-mg form used, dosage increased 850 mg every other week to maximum dose of 2,550 mg P.O. daily in divided doses, p.r.n.
Elderly:
for patients over age 65, dosing should be conservative because of potential decrease in renal function.
Adjust-a-dose:
For debilitated patients, dosing should be conservative because of potential decrease in renal function.

Adverse reactions
GI:
diarrhea, nausea, vomiting, abdominal bloating, flatulence, anorexia, unpleasant or metallic taste.
Hematologic:
megaloblastic anemia.
Other:
lactic acidosis.

Interactions
Drug-drug.
Calcium channel blockers, corticosteroids, estrogens, isoniazid, nicotinic acid, oral contraceptives, phenothiazines, phenytoin, sympathomimetics, thiazide and other diuretics, thyroid drugs: may produce hyperglycemia. Monitor patient's glycemic control. Metformin dosage may need to be increased.
Cationic drugs (such as amiloride, cimetidine, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, vancomycin):
have potential to compete for common renal tubular transport systems, which may increase metformin plasma levels. Monitor patient's blood glucose level.
Nifedipine:
increased metformin plasma levels. Monitor patient closely. Metformin dosage may need to be decreased.
Radiologic contrast dye:
can result in acute renal failure. Withhold metformin for 24 hours before procedure.
Drug-lifestyle.
Alcohol use: potentiated drug's effects. Avoid concurrent use.

Effects on diagnostic tests
None reported.

Contraindications
Contraindicated in patients with hypersensitivity to drug and in those with renal disease or metabolic acidosis. Drug should be temporarily withheld in patients undergoing radiologic studies involving parenteral administration of iodinated contrast materials because use of such products may result in acute renal dysfunction. Drug should be promptly discontinued if patient enters a hypoxic state. Avoid use in patients with hepatic disease.

Nursing considerations

Patient teaching

*Liquid contains alcohol. **May contain tartrazine.  †Canada  ‡Australia  §U.K.  OTCOver the counter
Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE-THREATENING

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