Warfarin

Question 1

What ?

Answer 1

Vitamin K antagonist

Takes 48-72hrs to work

Question 2

Tablets

Answer 2

white = 0.5mg 
brown = 1mg 
blue = 3mg 
pink = 5mg

Question 3

Dose

Answer 3

5mg initially and monitor 1-2 days

maintenance 3-9mg at same time each day

Question 4

Monitoring

Answer 4

INR every 3 months once stable

Question 5

Duration of treatment

Answer 5

isolated calf DVT = 6 weeks 
provoked DVT (COCs, pregnancy, leg cast) = 3 months 
Unprovoked (AF) = 3 months / long-term

Question 6

Target INR

Answer 6

2. 5 = VTE, AF, MI, Cardioversion, bioprosthetic mitrial valve
3. 5 = recurrent VTE (on anticoag and INR >2)

Question 7

Patient counselling

Answer 7

yellow treatment booklet

anticoag alert card

Question 8

MRHA

Answer 8

1. Interaction with direct-acting antivirals to treat chronic Hep C = closely monitor INR
2. OTC miconazole gel (DAKTARIN) contraindication = closely monitor INR
   * enzyme inhibitor, increased anticoag effect of warfarin so increased bleeding risk
   * stop and seek immediate medical attention if any sign of bleeding e.g. nose bleed/blood in urine
3. Reports of calciphylaxis - report painful skin rash, consider stopping if calciphylaxis diagnosed, RF end-stage renal disease

Question 9

What to do if bleeding?

Answer 9

1. Stop warfarin
2. IV Phytomenadione (Vit K)
3. Dried prothrombin complex or fresh frozen plasma

Question 10

INR 5-8 and no bleeding

Answer 10

1. withhold 1-2 dose
2. reduce maintenance dose
3. measure IRN after 2-3 days

Question 11

INR 5-8 and minor bleed

Answer 11

1. omit warfarin
2. IV phytomenadione
3. repeat if IRN still >5 after 24hrs
4. restart warfarin when INR <5

Question 12

INR >8 and no bleed

Answer 12

1. Omit warfarin
2. ORAL phytomenadione
3. Repeat if INR >5 after 24hrs
4. restart warfarin when INR <5

Question 13

INR >8 and minor bleed

Answer 13

1. omit warfarin
2. IV phytomenadione
3. Repeat if INR >5 after 24hrs
4. restart warfarin once INR <5