Metformin

Question 1

what is metformin used for

Answer 1

Type 2 diabetes (1st choice medication for control of blood glucose or combined with other drugs e.g. gliclazide or insulin)

Question 2

How does metformin work?

Answer 2

• Metformin lowers blood glucose by increasing the response (sensitivity) to insulin.
• stops gluconeogenesis / glycogenolysis
• increase glucose uptake by muscles
• lowers GI glucose absorption
• reduces weight gain + stimulates weight loss.

Question 3

What are the side effects of metformin/

Answer 3

1) GI upset (nausea, vomiting, contsip, diarr, loss of appetite)
2) Lactic acidosis:
- recurrent illness causes metformin acculumation by worsening renal impairment,
- increased lactic production in sepsis, hypoxia, cardiac failure.
- reduced lactate metabolism (e.g. liver failure)

Question 4

A side effect of metformin is lactic acidosis, what are the causes of this?

Answer 4

Lactic acidosis:

• recurrent illness causes metformin acculumation by worsening renal impairment,
• increased lactic production in sepsis, hypoxia, cardiac failure.
• reduced lactate metabolism (e.g. liver failure)

Question 5

What conditions is metformin contraindicated in?

Answer 5

1) Severe renal impairment (metformin is excreted unchanged by the kidneys, so in reduced renal function, metformin remains in the system)
2) Acute kidney injury (sepsis, dehydration)

Question 6

Why should caution be taken with metformin in liver impairment?

Answer 6

In hepatic impairment clearance of lactate may be reduced this can lead to lactic acidosis.

Question 7

Why should metformin be withheld in acute alcohol intoxication?

Answer 7

reduced liver function, so impaired clearance of lactate —> lactic acidosis.

Question 8

Why should metformin be use in caution with chronic alcohol overuse?

Answer 8

there is increased risk of hypoglycaemia

Question 9

What are the drug interactions of metformin?

Answer 9

-metformin should be witheld 48 hrs before and after contrast IV media (CT scans) when there is renal impairment or risk of lactic acidosis.

Caution with drugs that impair renal function:

• ACE i
• NSAIDs
• Diuretics

Drugs that raise blood glucose:

• prednisolone
• thiazide diuretic
• loop diuretic

Question 10

how is metformin taken?

Answer 10

Orally

with or after food

Question 11

How is metformin monitored?

Answer 11

HbA1c (target <58mmol/l)
Safety:
measure renal function before starting treatment then annually.