warfarin

Question 1

1mg~2mg x 1wk (expected sensitivity to warfarin)
for what population

Answer 1

> 75y
High bleeding rsk
CHF
Liver or kidney disease
Poor nutritional status
low albumin level
Baseline INR not within 0.8-1.2 , possible clotting deficiency
Indian, overweight (lower INR – HIGHER dose needed)
Current thyroid storm, infection, CYP inh (higher iNR - lower dose now)

Question 2

When to add clexane with initiating warfarin

Answer 2

ACE, VTE, bridging OAC with mechanical heart/valves/ high TE risk/ active clot (complete 5d bridging!)

Question 3

high TE risk

Answer 3

AF with CHADVASC ≥7
AF with stroke/ TIA
recurrent stroke or <3m
mechanical valve replacement
intracardiac thrombus
rheumatic mitral stenosis
recurrent VTE or <3m
chronic TE pulmonary HTN, arterial thromboembolism, artificial bypass graft
APS, deficiency clots

Question 4

moderate TE

Answer 4

non-valvular AF CHADVASC 5-6
VTE within 3-12m

Question 5

low TE

Answer 5

non-valvular AF CHADVASC <4, no stroke
stroke without AF >9m
VTE >12m

Question 6

Pt bleeding risk - HIGH

Answer 6

procedure with high bleed risk
severe renal impairment/ liver
hx of bleeding: anemia, thrombocytopenia, bleed event within 3m
active cancer
>75y

Question 7

high vs mod TE clexane dose

Answer 7

High TE: therapeutic dose 1mg/kg BD or OD based on crcl
Mod TE: prophylactic dose 40mg or 30mg based on crcl

Question 8

warfarin > DOAC, LMWH, IV heparin

Answer 8

INR <2 stop warfarin, start DOAC
INR2-3 stop warfarin, start DOAC 1 DAY AFTER
INR>3, repeat INR

Question 9

dabig > warfarin

Answer 9

crcl > 50, start warfarin 3d after stopping dabig

crcl 30-50, start warfarin 2d after stopping dabig

Question 10

rivaox > warfarin

Answer 10

stop rivarox, start clexane
INR >2

Question 11

apix > warfarin

Answer 11

concurrent for 2d
INR 3rd day, until >2

Question 12

INR goals 2.5-3.5

Answer 12

mechanical Mitral replacement

Risk factors for thromboembolism (AF, anterior-apical STEMI, left atrial enlargement, hypercoagulable state, low EF)

Question 13

short term warfarin

Answer 13

bioprosthetic mitral valve replacement (3m > aspirin 100mg/d)

until thrombus resolves

Large anterior MI, significant heart failure,
intracardiac thrombus, AF, history of
thromboembolic event (3m)

DVT, PE (provoked 3-6m), (unprovoked 6-12m)

Question 14

Dabigatran dose AF

Answer 14

CrCl >30 mL/min:
150mg twice daily

If age ≥80 years:
110mg twice daily

CrCl <30 ml/min:
Avoid use

Question 15

dabig DVT

Answer 15

CrCl > 30ml/min:
Parenteral anticoagulant x 5-10 days then 150mg twice daily

Question 16

dabig prophy dose

Answer 16

CrCl >30 mL/min:
150 mg twice daily

Question 17

rivarox AF dose

Answer 17

CrCl > 50ml/min:
20mg once daily

CrCl 15-50 ml/min:
15mg once daily

CrCl <15 ml/min:
Avoid use

Question 18

rivarox DVT dose

Answer 18

CrCl ≥ 30ml/min:
15mg twice daily x 21
days then 20mg once
daily

Question 19

rivarox prophy dose

Answer 19

CrCl ≥ 30ml/min:
10mg once daily

We do not have the 10mg tablet. (½ of 20mg tablet)

The 2.5mg dose is for pts that have Peripheral Artery Disease done stenting, for DAT (Dual Antithrombotic Therapy).

Question 20

apix AF

Answer 20

CrCl > 30ml/min:
5mg twice daily

Fulfill at least 2 of the
following:
Age ≥80 years
Body weight ≤60kg
Serum creatinine ≥133umol/L
2.5mg twice daily

CrCl 15-30ml/min:
2.5mg twice daily

CrCl <15 ml/min:
Avoid use

Question 21

apix DVT tx dose

Answer 21

crCl > 25ml/min:
10mg twice daily x 7 days
then 5mg twice daily

Question 22

Apix prophy

Answer 22

CrCl > 25ml/min:
2.5mg twice daily

Question 23

pain

Answer 23

incr INR

Question 24

hepatic impairment

Answer 24

incr INR
Decreased clotting factor synthesis and warfarin metabolism

Question 25

fever/ infection

Answer 25

incr INR Increased catabolism and reduced level of clotting factors

Question 26

hypoalbuminuria

Answer 26

incr INR Warfarin is highly protein bound (Low albumin = more free warfarin)

Question 27

fluid retention gut

Answer 27

decr INR

Question 28

thyroid HYPER

Answer 28

incr INR increases clotting factor turnover

Question 29

HF/ liver congestion

Answer 29

incr INR decr warfarin metabolism

Question 30

GI diarrhea

Answer 30

inr INR increases elimination of gut vitamin K

Question 31

activity lvl

Answer 31

reduce INR Increased metabolism including warfarin Induction of CYP enzymes

Question 32

alcohol binge

Answer 32

blip incr INR alcohol inhibits the liver enzyme system responsible for metabolizing warfarin.

Question 33

chronic drinking

Answer 33

decr INR chronic, heavy alcohol use increases the liver's metabolism of warfarin, clearing it faster.

Question 34

CYPC29, VKORC1

Answer 34

CYP2C9, the principal enzyme that metabolizes warfarin -- PM=incr INR VKORC1, the target protein inhibited by warfarin -- more sensitive = incr INR

Question 35

incr vit k/ oral intake/ feeds

Answer 35

decr INR

Question 36

smoking

Answer 36

decr INR Cigarette smoke induces warfarin metabolism via CYP enzymes

Question 37

major bleed

Answer 37

Fatal/hemodynamic instability Symptomatic bleeding in critical organs such as: Intracranial Intraspinal Intraocular Retroperitoneal Intraarticular Pericardial Intramuscular with compartment syndrome ↓Hb ≥2g/dL

Question 38

when to vit k

Answer 38

Omit warfarin and administer 1-3mg of oral vitamin K. Check INR in 24 hours.

Question 39

CYP inducers eg and effect on INR

Answer 39

rifampicin, CBP, st john wort, ginger, ginseng reduce INR

Question 40

CYP inhibitors eg and effect on INR

Answer 40

cipro, macrolides, doxy, metronidazole, PPI, amiodarone, allopurinol, grapefruit, SSRI/TCA, azole, steroids, paracetamol >2g incr INR

Question 41

Competitively block or displace warfarin at plasma protein binding sites eg and effect on INR

Answer 41

Sulfonamides (sulfamethoxazole/ trimethoprim**) Sulfonylureas Phenytoin incr INR

Question 42

high k foods > 100mcg per 100g human daily about 100mcg

Answer 42

brocoli, kale, lettuce, spinach, seaweed, watercress avocado, kiwi beef/ pork liver beans soybean oil, mayo, canola oil green tea > 2L, HL milk , herbal pistachio