Metformin Hydro Chloride

metformin hydrochloride (met fore' min) Glucophage, Glucophage XR, Riomet Pregnancy Category B Drug class

Antidiabetic Therapeutic actions

Exact mechanism is not understood; possibly increases peripheral utilization of glucose, increases production of insulin, decreases hepatic glucose production and alters intestinal absorption of glucose. Indications

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Adjunct to diet to lower blood glucose with type 2 (non–insulin-dependent) diabetes mellitus in patients > 10 yr; extended release in patients > 17 yr As part of combination therapy with a sulfonylurea or insulin when either drug alone cannot control glucose levels in patients with type 2 diabetes mellitus

Contraindications and cautions

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Contraindicated with allergy to metformin; CHF; diabetes complicated by fever, severe infections, severe trauma, major surgery, ketosis, acidosis, coma (use insulin); type 1 (insulin-dependent), serious hepatic impairment, serious renal impairment, uremia, thyroid or endocrine impairment, glycosuria, hyperglycemia associated with primary renal disease; labor and delivery (if metformin is used during pregnancy, discontinue drug at least 1 mo before delivery); lactation (safety not established).

Available forms

Tablets—500, 850, 1,000 mg; extended-release tablets—500 mg; oral solution— 100 mg/mL Dosages ADULTS

500–850 mg/day PO in divided doses to a maximum of 2,550 mg/day. Dose should be adjusted based on response and blood glucose level. ER tablet: Initially 500 mg/day PO with the evening meal; may be increased by 500 mg each wk to a maximum of 2,550 mg once daily. PEDIATRIC PATIENTS 10–16 YR

500 mg/day PO in divided doses with meals; may be increased by 500 mg each wk to a maximum of 2,000 mg/day. ER tablet is not recommended. GERIATRIC PATIENTS AND PATIENTS WITH RENAL IMPAIRMENT

Smaller doses may be necessary; monitor closely and adjust slowly. Pharmacokinetics Route

Peak

Duration

Oral

2–2.5 hr

10–16 hr

Metabolism: Hepatic; T1/2: 6.2 and 17.6 hr Distribution: Crosses placenta; enters breast milk Excretion: Urine Adverse effects

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Endocrine: Hypoglycemia, lactic acidosis GI: Anorexia, nausea, vomiting, epigastric discomfort, heartburn, diarrhea Hypersensitivity: Allergic skin reactions, eczema, pruritus, erythema, urticaria

Interactions

Drug-drug • Increased risk of hypoglycemia with cimetidine, furosemide, cationic drugs such as digoxin, amiloride, vancomycin • Increased risk of lactic acidosis with glucocorticoids or ethanol • Increased risk of acute renal failure and lactic acidosis with iodinated contrast material used in radiologic studies; stop metformin for 48 hr before and after such studies Drug-alternative therapy • Increased risk of hypoglycemia if taken with juniper berries, ginseng, garlic, fenugreek, coriander, dandelion root, celery Nursing considerations Assessment

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History: Allergy to metformin; diabetes complicated by fever, severe infections, severe trauma, major surgery, ketosis, acidosis, coma; type 1 diabetes, serious hepatic or renal impairment, uremia, thyroid or endocrine impairment, glycosuria, hyperglycemia associated with primary renal disease, CHF, pregnancy, lactation Physical: Skin color, lesions; T, orientation, reflexes, peripheral sensation; R, adventitious sounds; liver evaluation, bowel sounds; urinalysis, BUN, serum creatinine, liver function tests, blood glucose, CBC

Interventions

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Monitor urine or serum glucose levels frequently to determine effectiveness of drug and dosage. Arrange for transfer to insulin therapy during periods of high stress (infections, surgery, trauma). Use IV glucose if severe hypoglycemia occurs as a result of overdose.

Teaching points

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Do not discontinue this medication without consulting your health care provider. Monitor urine or blood for glucose and ketones as prescribed. Do not use this drug during pregnancy; if you become pregnant, consult with your health care provider for appropriate therapy.

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Avoid using alcohol while taking this drug. Report fever, sore throat, unusual bleeding or bruising, rash, dark urine, lightcolored stools, hypo- or hyperglycemic reactions.

Adverse effects in Italic are most common; those in Bold are life-threatening.