Endocrine: insulin, metformin

Question 1

Common indications of insulin?

Answer 1

Type 1 diabetes
- insulin replacement

Type 2 diabetes (if oral hypoglycaemic tx is inadequate/resistant -poorly controlled)

For diabetic emergencies, for e.g:
- diabetic ketoacidosis
- hyperglycaemic hyperosmolar syndrome
- perioperative glycaemic control

Hyperkalaemia (insulin given alongside glucose)

Question 2

Warnings of insulin?

Answer 2

Renal impairment
- reduce insulin clearance, so increased risk of hypoglycaemia

Question 3

Adverse effects of insulin?

Answer 3

Hypoglycaemia (can lead to coma and death)

Lipohypertrophy (fat overgrowth if repeated SC injection at the same site)

Question 4

Important interactions of insulin?

Answer 4

Combining insulin with other hypoglycaemic agents increase the risk of hypoglycaemia.

Concurrent therapy with systemic corticosteroids increase insulin requirements.

Question 5

List the forms of insulin?

Answer 5

Rapid
Short
Intermediate
Long
Biphasic
IV insulin requirement

Question 6

What is rapid acting insulin? Example?

Answer 6

Immediate onset

Short duration

NovoRapid

Question 7

What is short acting insulin? Example?

Answer 7

Early onset (2-3 hour delay to peak effect)

Short duration

E.g. Actrapid (soluble insulin)

Question 8

What is intermediate acting insulin? Example?

Answer 8

Intermediate onset

Intermediate duration

E.g. Isophane or NPH insulin (Humulin I)

Question 9

What is long acting insulin? Example?

Answer 9

Flat profile with regular administration

Long duration

E.g. Insulin glargine (Lantus) or Insulin detemir (Levemir)

Question 10

What is biphasic insulin? Example?

Answer 10

Mix of rapid and immediate acting insulin

E.g. NovoMix

Question 11

What is IV insulin requirement? Example?

Answer 11

E.g. Actrapid (soluble insulin)

Question 12

How is insulin prescribed/administered?

Answer 12

Basal-bolus regimen
- Lantus = long-acting; low basal level (inject once per day)

• NovoRapid = rapid-acting; given before each main meal
• SC injection, self administration

Question 13

How is insulin monitored?

Answer 13

Pt should measure capillary blood glucose regularly and adjust insulin dose based on results.
- Check at least 4 times a day before meals (4-7 mmol/L) and before going to bed.

Measure HbA1c (≤48mmol/mol) annually to assess long-term glycaemic control.

Monitor potassium level every 4 hours if IV insulin infusion.

Question 14

How would you explain to pt starting on insulin?

Answer 14

Insulin helps control blood sugar levels and prevents complications.

Advise lifestyle measures:
- healthy, balanced diet, regular exercise

Warn about hypoglycaemia and to watch out for signs (e.g. dizziness, agitation, nausea, sweating, confusion).
- If hypoglycaemia occurs, tell pt to have something sugary (e.g. glucose tablet, sugary drink), then have something starchy (e.g. sandwich).

Question 15

Mechanism of action for insulin?

Answer 15

Diabetes mellitus:
- Stimulates glucose uptake from the circulation into tissues, including skeletal muscle and fat.

• Increases the use of glucose as an energy source.
• Insulin stimulates glycogen, lipid and protein synthesis and inhibits gluconeogenesis and ketogenesis.

Hyperkalaemia:
- Insulin causes potassium ions to enter cells, reducing the serum concentration.

Question 16

Indications of metformin?

Answer 16

Type 2 diabetes

Question 17

Mechanism of action for metformin?

Answer 17

Type of biguanide.

Lowers blood glucose by:
- reducing hepatic glucose output (glycogenolysis and gluconeogenesis).

• Increasing glucose uptake and utilisation by skeletal muscle.

Metformin activates AMP kinase (adenosine monophosphate-activated protein kinase).

Question 18

Adverse effects of metformin?

Answer 18

GI upset
- n+v
- taste disturbance
- anorexia
- diarrhoea

Lactic acidosis

Weight loss

Question 19

Warnings of metformin?

Answer 19

Caution in:
- renal impairment (reduce dose in eGFR <45; stop drug if eGFR <30)
- hepatic impairment
- chronic alcohol abuse

Withold metformin in:
- AKI
- severe tissue hypoxia
- acute alcohol intoxication

Question 20

Interactions of metformin?

Answer 20

Metformin must be withheld:
- before and 48hours after injection of IV contrast media.
- increased risk of renal impairment
- metformin accumulation
- lactic acidosis

Other drugs might impair renal function:
- ACEi
- NSAIDs
- diuretics

Other drugs that elevate blood glucose can oppose the actions and reduce efficacy of metformin:
- prednisolone
- thiazide
- loop diuretics

Question 21

Monitoring of metformin?

Answer 21

Assess HbA1c

Target for type 2 diabetes is usually <48 mmol/mol.

Add another drug if HbA1c >58 mmol/mol, so new target will be <53mmol/mol.

Safety:
- renal function before and starting tx, then annually.

Question 22

Pt education on metformin?

Answer 22

Long-term tx to help control blood sugar and reduce the risk of diabetic complications.

Must maintain healthy, balanced diet, and regular exercise.

Seek urgent medical advice if they develop any significant illness (e.g. fever, chest pain, SOB). Investigate and treat illness.

Metformin may need to be stopped/withheld due to lactic acidosis.

Metformin may need to be stopped before having an x-ray or operation, so inform doctor early on.