METFORMIN

Biguanide oral antidiabetic medicine. It works by decreasing the production of glucose and increasing the utilisation of glucose by the peripheral cells.

Dosage Forms

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Tablet

500 mg

Uses

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  • Type II diabetes mellitus

Dose and Duration

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Type II diabetes

Adult and child > 10 years: initially 500 mg with breakfast for at least 1 week, then 500 mg with breakfast and evening meal for at least 1 week; then 500mg with breakfast, lunch and evening meal.
Maximum 2 g daily in divided doses

Child 8–10 years: initially 200 mg once daily adjusted according to response at intervals of at least 1 week (max 2 g daily in 2–3 divided doses)

Contraindications

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  • Ketoacidosis
  • General anaesthesia
  • Iodine-containing x-ray contrast media
  • Moderate to severe renal impairment
  • Alcohol dependency
  • Disease that may cause tissue hypoxia (e.g. heart failure, respiratory failure, recent myocardial infarction, shock)

Side Effects

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  • Nausea, vomiting, diarrhoea, abdominal pain, taste disturbance
  • Decreased vitamin B12 absorption
  • Itching
  • Lactic acidosis

Patient Instructions

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  • Continue diet restrictions and exercise recommendations
  • Always take metformin with meals
  • Gastro intestinal side effects usually go away as you continue taking the medicine so do not worry

Pregnancy

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  • Can be used

Breast-feeding

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  • Can be used

⚠️ Caution

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  • May cause lactic acidosis in renal impairment
  • Determine renal function before treatment and at least once a year during treatment
  • Suspend metformin on morning of surgery and restart when renal function returns to normal
  • Iodinated contrast media may cause kidney failure, which can increase the risk of lactic acidosis with metformin. Suspend metformin prior to the test; restart no earlier than 48 hours after the test and renal function has returned to normal
  • Insulin is always required in medical and surgical emergencies e.g. during infections
  • During pregnancy, it is preferable to use insulin so as to achieve as normal as possible blood glucose concentrations