anticoagulation

Question 1

How does warfarin act?

Answer 1

It inhibits vitamin K epoxide reductase in the liver. Which is a necessary enzyme for the activation of a multiple coagulation factors (II, VII, IX, X)

Question 2

How long should warfarin be used in a provoked DVT? Temporary risk factors known.

Answer 2

3 months

Question 3

How long should warfarin be used in an unprovoked DVT?

Answer 3

3 months - maybe long term

Question 4

How long should warfarin be used if recurrent DVT on warfarin, AF, Mechanical heart valve with or without r other risk factors for clotting?

Answer 4

long term
INR target increases by 0.5 with extra risk factors
mitral valve replace is higher risk of clotting - increased target INR by 0.5

Question 5

What questions do you need to ask when prescribing warfarin?

Answer 5

• Indication for treatment
• rapid loading or slow loading needed?
• Any reason’s the patient would be sensitive to warfarin
  
  • age >70 (esp. 80)
  • drug interactions
  • hepatic impairment
  • sever cardiac failure
  • TPN
  • Low albumin
  • Low BMI

Question 6

describe some pharmcokinetics (or the other one) of Warfarin.

Answer 6

• protein bound

- long half-life of 40 hours

Question 7

When is a loading dose more appropriate than not and vice versa?

Answer 7

• loading doses needed in situations where urgent anticoagulation is required
  
  • acute DVT/PE
  • Valve replacement
• not required in AF

Question 8

When is specialist management of warfarin required?

Answer 8

-greater than 21mg maintenance dose indicated a warfarin resistance

Question 9

What are the colours and doses of the warfarin tablets? (THIS QUESTION IS FOR FUTURE CLINICAL PRACTICE NOT FOR EXAMS)

Answer 9

get’s stronger as it gets more flamboyant

• white = 500 micrograms
• brown = 1mg
• Blue = 3 mg
• pink = 5mg

Question 10

what’s the deal with warfarin and surgical procedures?

Answer 10

• minor surgeries (cataracts) don’t require change in warfarin
• major invasive interventions warfarin should be stopped 4-5 days before hand
• LMWH can be used to prevent thrombosis perioperatively

Question 11

Advice for missed dose or too much warfarin?

Answer 11

• omit missed dose, record in yellow book, take the next dose as per normal scheduling
• contact warfarin clinic (or usual port of call for warfarin management) if the dose taken greatly exceeds normal dose

Question 12

What advice about diet should patients on warfarin receive?

Answer 12

• take foods that are high in Vit K in moderation
• chickpeas, leafy greens, liver, cranberry juice, brocolli
• sudden dietary changes may affect INR too
• it is dangerous too binge drink as it increases the metabolism of warfarin
• normal alcohol consumption (within national guidelines) is safe.

Question 13

When should one monitor an INR?

Answer 13

• daily for 4 days if a high loading dose regime is used
• measure at day 4 if slow loading regime used
• once stable measure every 4-12 weeks depending on local guidelines
• check INR if a new drug is started or stopped