Warfarin

Question 1

Warfarin: Action

Answer 1

Blood thinner

Does so by blocking vitamin k (Vit k antagonist) which is used by proteins in the blood called clotting factors, these are used to clot the blood

Alters the INR - a measure of the time for blood to clot

Question 2

Warfarin: indication

Answer 2

Prophylaxis of embolization

• rheumatic heart disease
• AF

Prophylaxis after insertion of prosthetic heart valve

Treatment for DVT / PE

Question 3

Warfarin: where metabolised

Answer 3

Liver

Question 4

Warfarin: timeline

Answer 4

OD - usually in the evening

Question 5

Warfarin: how to take

Answer 5

Tablet

Question 6

Warfarin: length of treatment

Answer 6

3 months for DVT
6 months for PE
Lifelong for AF

Question 7

Warfarin: how long till effects

Answer 7

2-3 days

Question 8

Warfarin: tests

Answer 8

Before starting: clotting screen (prothrombin time), U&Es, LFTs, FBC, BP, renal function

Start 5mg for 4days then test INR on day 5 and 8 - adjust dose according to INR

If require a immediate effect then start LMWH to cover

Target INR varies for different conditions

Monitor INR if additional medication given

Be cautious in renal and liver failure

Question 9

Warfarin: important side effects

Answer 9

Haemorrhage (1-2%)
- advise to see doctor if any unusual bleeding eg Brussels, dark stools, cuts take longer to heal

GI upset - nausea, diarrhoea, rash, hair loss

Many drug interactions - mainly with CYP p450 inducers/inhibitors, steroids

Caution in liver and renal failure

Question 10

Warfarin: complications and contraindications

Answer 10

Complications: bleeding

Contraindications

• pregnancy
• haemorrhagic stroke
• significant bleeding

Caution: patients at high risk of falling

Question 11

Warfarin: Supplementary advice

Answer 11

Avoid liver, spinach, cranberry juice, alcohol binges
- can affect INR

No NSAIDs or Aspirin

Give a yellow anticoagulant book