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Metformin

Editor: Updated Class:

ADMINISTRATION ROUTES:

PO

ALTERNATIVE NAMES:

Arrow Metformin

ICU INDICATIONS:

  1. Type 2 diabetes mellitus

PRESENTATION AND ADMINISTRATION:

PO:

Metformin 250 mg, 500 mg, 850 mg and 1000 mg tablets

DOSAGE:

PO:

500 mg OD or BD

Increase to max 1000 mg TDS

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

Dose in renal impairment

GFR (ml/min) DOSE
<10 do not use
10-40 do not use
>40-50 25-50% of dose

Dose in renal replacement therapy

MODALITY DOSE
CAPD do not use
HD do not use
CVVHDF do not use

DOSAGE IN PAEDIATRICS:

PO:

Not applicable

CLINICAL PHARMACOLOGY:

Metformin is an antihyperglycaemic agent which improves glucose tolerance in patients with Type 2 diabetes, lowering both basal and postprandial plasma glucose. Its pharmacologic mechanisms of action are different from other classes of oral antihyperglycaemic agents. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.

CONTRAINDICATIONS:

  1. Renal dysfunction
  2. Congestive heart failure requiring pharmacologic treatment
  3. Known hypersensitivity to metformin
  4. Acute or chronic metabolic acidosis including diabetic ketoacidosis
  5. Use of intravenous contrast for angiography or CT if eGFR <30 mL/min

WARNINGS:

Lactic Acidosis

Lactic acidosis is a rare, but serious, metabolic complication that can occur due to metformin accumulation. When it occurs, it is fatal in approximately 50% of cases

PRECAUTIONS:

General:

Surgical Procedures

Metformin therapy should be temporarily suspended for any surgical procedure (except minor procedures not associated with restricted intake of food and fluids) and should not be restarted until the patient's oral intake has resumed and renal function has been evaluated as normal.

Hypoglycaemia

Hypoglycaemia does not occur in patients receiving metformin alone under usual circumstances of use, but could occur when caloric intake is deficient, when strenuous exercise is not compensated by caloric supplementation, or during concomitant use with other glucose-lowering agents (such as sulfonylureas and insulin)

Laboratory Tests:

No tests in addition to routine ICU tests are required

Drug/Laboratory Test Interactions:

None noted

IMPORTANT DRUG INTERACTIONS IN ICU:

None of note

ADVERSE REACTIONS:

Gastrointestinal:

Diarrhoea, nausea, vomiting, flatulence, abdominal discomfort

Metabolic and endocrine:

Lactic acidosis, hypoglycaemia