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bnf 2021 > 2. Warfarin > Flashcards

2. Warfarin Flashcards

1
Q

Warfarin

MOA

A

Warfarin competitively inhibits the vitamin K epoxide reductase complex 1 (VKORC1), which is an essential enzyme for activating the vitamin K available in the body. Through this mechanism, warfarin can deplete functional vitamin K reserves and therefore reduce the synthesis of active clotting factors

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2
Q

Warfarin

0.5mg tablet colour

A

White

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3
Q

Warfarin

1mg tablet colour

A

Brown

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4
Q

Warfarin

3mg tablet colour

A

Blue

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5
Q

Warfarin

5mg tablet colour

A

Pink

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6
Q

Warfarin

How long to start working in body? (Hrs)

A

48-72hrs

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7
Q

Warfarin LD

A

5mg 1-2 days
Then
3-9mg OD
everyday on the same time

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8
Q

How to take warfarin

A

1 full glass of water

Never double the dose

Always carry yellow book

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9
Q

Warfarin

What to monitor (6)

A

INR on first day, the alternate days then longer up to 12 weeks

Liver function

Renal function

Full blood count

BP

thyroid function

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10
Q

Warfarin

Target INR

Normal

VTE, AF, MI, cardioversion

Recurrent DVT or PE

A
  1. 1 or less
  2. 5
  3. 5
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11
Q

Warfarin

Target INR which condition?

  1. 1 INR
  2. 5 INR
  3. 5 INR
A

Normal

VTE, AF, MI, cardioversion

Recurrent DVT or PE

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12
Q

Warfarin

Duration

Isolated calf-vein DVT

Venous thromboembolism PROVOKED by surgery
Or other risk: combined pill, plaster cast or pregnancy

Unprovoked DVT or PE

A

6 weeks

3 months

3 months + (may be required long term)

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13
Q

Warfarin

Warning ⚠️
Report ASAP

May need antidote

A
  1. Haemorrhage
Nosebleeds 
Bruising 
Bleeding wounds 
Haemorrhage stroke
(Headache, confusion)
  1. DVT or PE
    (Pain, swelling, tenderness in calf; SOB, chest pain, red skin)
  2. Rash, skin necrosis, purple toes
  3. Diarrhoea- Vomiting
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14
Q

Warfarin

Antidote

A

Phytomenadione
(Vit k)

Slow IV 5mg

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15
Q

Warfarin in
Pregnancy

Baby?

A

Avoid and caution in first trimester,

Best avoided but if benefit Overweight risk only given in 3rd trimester

Babies of mothers taking warfarin at the time of delivery need to be offered immediate prophylaxis with intramuscular phytomenadione (vitamin K1).

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16
Q

Warfarin

Breastfeeding

A

Not present in milk in significant amounts and appears safe.

Risk of haemorrhage which is increased by vitamin K deficiency.

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17
Q

Warfarin

Hepatic impairment

A

In general, manufacturers advise caution in mild to moderate impairment;

avoid in severe impairment.

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18
Q

Warfarin

Renal impairment

A

Use with caution in mild to moderate impairment.

Monitoring
In severe renal impairment, monitor INR more frequently.

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19
Q

Warfarin

+

Vitamin K

A

Reduced anticoagulant effect

20
Q

Warfarin

+

Vitamin E

A

Increased anticoagulant effect

21
Q

Warfarin

Interaction

Increased and decreased plasma concentration (2)

A

Corticosteroids

Cholestyramine

Clopidogrel

22
Q

Warfarin

Interaction with underlying conditions
Enhanced ⬆️ plasma concentration) (9

A

Hyperthyroidism

Low vitamin K intake

Poor nutritional state

Diarrhea

Liver disease

Congestive heart failure

Cancer

Connective tissue diseases

High fever

23
Q

Warfarin

Interaction enhanced plasma concentration (⬆️ bleeding risk)

Drugs

A 
Amiodarone 
Paracetamol 
Anabolic steroids
Azithromicin 
Cephalogrel
Cimetidine 
Clarithromicin 
Clopidogrel 
High dose corticosteroids 
Cranberry juice
Dipyridamole 
Erythromycin
Esomeprazole 
Fibrates 
Fluconazole
Fluvastatin
Itraconazole 
Methylphenidate 
Metronidazole 
Miconazole (including topical use)
NSAIDs
Omeprazole 
Propafenone 
Rosuvastatin
SSRIs
St John Wort
Tamoxifen 
Testosterone 
Thyroid hormones
Tetracyclines
Tramadol 
Venlafaxine
24
Q

Warfarin

Interaction (reduced plasma concentration ⬇️= clot risk)

A 
Acictretin
Azathioprine 
Carbamazepine 
Clopidogrel
Griseofulvin 
Mercaptopurine 
Phenobarbital 
Phenytoin 
Rifamycin 
Succalfate
 Vitamin k
25
Q

Warfarin

+

Surgery

Elective

A

Elective:
Stop warfarin 5 days before surgery

Give oral Vit K (phytonadione) surgery day

If INR >1.5

Restart warfarin on evening or next day

26
Q

Warfarin

+

Surgery

Emergency

A

Delay dose by 6-12hrs

If can’t delay give IV phytonadione + dried prothrombin complex

27
Q

Warfarin
High risk VTE

+

Surgery

A

If had VTE in last 3 months
OR
AF/TIA/mechanical valve

Stop warfarin 24hrs before surgery

Treat with:
“Bridge”

Lmwh dose I stress of warfarin

28
Q

Warfarin

+

Surgery

High risk bleeding

A

LMWH 48 hrs AFTER surgery

29
Q

Anticoagulants

SE

A 
passing blood in your urine.
passing blood when you poo or having black poo.
severe bruising.
prolonged nosebleeds.
bleeding gums.
vomiting blood or coughing up blood.
heavy periods in women.
30
Q

Anticoagulants

Examples

A

dabigatran (= direct thrombin inhibitor)

edoxaban (= direct Xa factor inhibitors)
rivaroxaban
Apixaban
warfarin

31
Q

Warfarin and birth

A

Take warfarin

After 48 hours of postpartum

32
Q

Warfarin half-life

A

40 hrs

33
Q

Warfarin form

A

Only Tablets

34
Q

Warfarin

Why CI in pregnancy especially 1st trimester

A

Crosses placenta

35
Q

Half life:

dabigatran (= direct thrombin inhibitor)

edoxaban (= direct Xa factor inhibitors)
rivaroxaban
Apixaban
warfarin

A

dabigatran 13hrs

edoxaban 10-14hrs
rivaroxaban young adult: 5-9hrs/ elderly: 13hrs
Apixaban 12 hrs
warfarin 40 hrs

36
Q

Dabigatran
Apixaban
Rivaroxaban

Indicated in?

A

Prophylaxis of venous thromboembolism

following total knee replacement surgery

37
Q

Edoxaban

Indication

A

Tx and prophylaxis of DVT
Stroke, non vascular AF

Dose adjustments due to interactions
Manufacturer advises max. dose of 30 mg once daily with concurrent:

ciclosporin,
dronedarone,
erythromycin
ketoconazole

38
Q

Warfarin

INR 5-8

And

NO bleed

A

Withhold 1-2 doses

Reduce maintenance dose

Check INR in 2-3 days

39
Q

Warfarin

INR >8

And

NO bleed

A

Stop warfarin

Take oral phytonadione

Repeat if INT still high after 24hrs

Restart warfarin if INR =5 or less

40
Q

Warfarin

INR 5-8 or INR >8

And

bleed

A

Stop warfarin

IV phytonadione

Repeat if INR still high in 24hrs

Restart warfarin when INR =<5

41
Q

heparin

Antidote

A

Protamine

42
Q

Heparin

Eliminated through?

A

Renal

43
Q

Warfarin

Eliminated by?

A

Hepatic (liver)

44
Q

Warfarin

can cause a serious skin rash
What is it called?

IMMEDIATE REFERRAL!!!!

A

Calciphylaxis (kal-sih-fuh-LAK-sis)

is a serious, uncommon disease in which calcium accumulates in small blood vessels of the fat and skin tissues.

Calciphylaxis causes blood clots, painful skin ulcers and may cause serious infections that can lead to death

45
Q

Rivaroxaban

Catheter after surgery when to take it out?

When to start given it after Removing the catheter

A

Wait atleast 18hrs after rivaroxaban dose to remove the catheter;

Wait 6 hrs after catheter removed and then give next rivaroxaban dose

bnf 2021 (20 decks)

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