BLOOD: WARFARIN

Question 1

WARFARIN: INDICATIONS

Answer 1

• Prevent clot extension and recurrence in DVT + PE
• To prevent embolic complications in AFib
• To prevent embolic complications after HEART VALVE REPLACEMENT (ST for tissue valve replacement, LT for mechanical valve replacement)

Question 2

WARFARIN: MOA

Answer 2

• Inhibits Vit K epoxide reductase

- Inhibits factor 2, 7, 9 and 10 production

Question 3

WARFARIN: ADVERSE EFFECTS

Answer 3

• Bleeding (slight excess increases risk of bleeding from existing abnormalities such as peptic ulcers or following minor trauma - intracerebral haemorrhage after head injury)

Question 4

WARFARIN: WARNINGS

Answer 4

• Immediate risk of haemorrhage, including > trauma and in patients requiring surgery
• Liver Dx patients
• Pregnancy (not in first trimester = fetal malformations)

Question 5

WARFARIN: INTERACTIONS

Answer 5

• Plasma concentration required to prevent clotting v close to concentration = Bleeding (LOW THERAPUTIC INDEX)
• Cytochrome P450 inhibitors = decrease warfarin metabolism and increase bleeding risk
  EXAMPLES: FLUCONAZOLE, MACROCLIDES
• Cytochrome P450 inducers = increase warfarin metabolism and risk of clots
  EXAMPLES: PHENYTOIN, CARBAMAZEPIN, RIFAMPICIN