Anticoagulants

Question 1

Warfarin inducers? (less drug)

Answer 1

CRAP gpS

C arbamazepine
R ifampicin
A lcohol - chronic
P henytoin

(griseolfin)
(phenobarbitone)
St John’s Wort & Sulfonylurea

Question 2

Warfarin inhibitors? (more drug)

Answer 2

SiCkfAcE.com + grapefruit juice

S imvastatin
         (isoniazid)
C iprofloxacin - tendonitis/rupture
         (ketconazole/antifungals)
         (fluoxetine)
A lcohol acute
         (cardiac/LF)
E rythromycin
         (sulphonamides & Na+ Valproate)
         (cimetidine)
         (omeprazole)
         (metronidazole)

Question 3

what is never prescribed w/ warfarin?

Answer 3

DOAC
prophylactic LMWH
therapeutic LMWH (unless “bridging”)

Question 4

normal INR?

Answer 4

0.8 - 1.2

Question 5

target INR in AF?

Answer 5

2 - 3

Question 6

target INR in metallic valve?

Answer 6

2.5-3.5 / 3-4

Question 7

if raised INR, but NOT bleeding, Tx for INR:

• <6
• 6 - 8
• > 8
• minor bleeding + INR>5?

Answer 7

• reduce dose
• omit dose for 2 days, then reduce
• oral Vit K 1-5mg
• IV Vit K 1-3mg

(restart doses when INR <5)

Question 8

Tx for bleeding, with any raised INR:

• minor
• major
• life threatening

Answer 8

• oral Vit K
• 5-10mg IV Vit K
• prothrombin complex concentrate (Beriplex)

Question 9

drugs that increase risk of bleeding even if INR in range?

Answer 9

NSAIDs
steroids
aspirin
clopidogrel

Question 10

how does warfarin work?

Answer 10

Vit K reductase inhibitor

• less reduced Vit K
• less 1972 factor production
• less of clotting cascade

Question 11

how does heparin or LMWH work?

Answer 11

activates antithrombin III & inhibits thrombin

- therefore less clotting cascade

Question 12

how do DOACs work?

Answer 12

inhibit factor Xa

• less prothrombin to thrombin
• less fibrin, less clots

Question 13

what drugs to STOP if Sx of bleeding/ tarry stools/ haemoptysis/ haemaemesis?

Answer 13

warfarin
DOAC
LMWH
antiplatelet

Question 14

what kind of thrombophrophylaxis is given on admission to hospital?

Answer 14

prophylactic LMWH (dalteparin 5000 U daily S/C)

compression stockings

Question 15

when would you not give compression stockings?

Answer 15

in PAD
(absent foot pulses)
may cause acute limb ischaemia

Question 16

monitoring when starting someone on warfarin?

Answer 16

INR daily, or alternate days, until 2-3 on two consecutive occasions

(a meaningful INR can only be obtained 3–4 days after starting Tx)

Then, twice weekly for 1–2 weeks (this should be continued if HT, RF or bleed risk)

Then, weekly measurements until > two INR measurements are 2-3

Thereafter, longer intervals (for example, < 12 weeks, if agreed locally)

Once stable, changes seldom required.

Question 17

painkiller to avoid prescribing with warfarin?

Answer 17

NSAID (stomach ulcers will be at risk of bleed)

Question 18

if INR is >1.5 perioperatively?

Answer 18

give 5mg oral Vit K

Question 19

when to stop warfarin before surgery?

when resumed?

Answer 19

5 days before (converted to tinzaparin/LMWH)

evening of surgery/next day

Question 20

what INR for surgery to go ahead?

Answer 20

<1.5

Question 21

is warfarin okay to take in pregnancy?

is warfarin safe in breastfeeding?

Answer 21

No! teratogenic

BF - yes

Question 22

what if rapid anticoagulation with warfarin is required?

Answer 22

Give 5 mg or 10 mg
once a day
for 2 days
remeasure INR on day three

Question 23

when an immediate effect is required from warfarin? (for example DVT, PE)

Answer 23

heparin/LMWH is given concomitantly for first 2 days, due to initial pro-coagulant affect of warfarin

(this is done in secondary care)

Question 24

examples of LMWHs?

Answer 24

dalteparin sodium
enoxaparin sodium
tinzaparin sodium

Question 25

what to prescribe as prophylaxis of DVT in medical patients? what if thy're on COCP? when to be cautious? what to avoid prescribing alongside?

Answer 25

dalteparin sodium 5000 units S/C every 24 hours (LMWH) stop COCP! bleeding risk - recent stroke DOACs

Question 26

which drugs are Xa inhibitors?

Answer 26

DOACs | -Xa-ban

Question 27

how to Tx VTE (DVT/PE)?

Answer 27

1) LMWH S/C dalteparin sodium approx 15,000 units (200 units/kg daily + max. per dose 18 000 units) 2) OR fondaparinux S/C (if body-weight 50–100 kg) 7.5 mg every 24 hours, usually warfarin started at the same time either should be continued for at least 5 days and until INR ≥ 2 for at least 24 hours

Question 28

how to Tx massive PE (haemodynamic instability)?

Answer 28

``` unfractioned heparin (UFH) + thrombolytic therapy (US‑enhanced, catheter‑directed thrombolysis) ``` if life threatening, occasionally surgical thrombectomy

Question 29

how to give VTE prophylaxis if patient has a phobia to needles?

Answer 29

apixaban PO 2.5 mg twice daily

Question 30

what to consider before prescribing NOACs?

Answer 30

eGFR

Question 31

Tx acute stroke?

Answer 31

CT <1 hr if no haemorrhage: <80 years and onset <4.5 hours ago consider thrombolysis (alteplase) Aspirin 300mg oral

Question 32

if INR > 1.5 on the day before surgery?

Answer 32

phytomenadione (vitamin K) 1–5 mg PO, using the IV preparation, is indicated

Question 33

if a pt on warfarin with INR in range is being Tx with clarithromycin?

Answer 33

continue warfarin at normal dose and re-check INR in 48 hours

Question 34

role of LMWH?

Answer 34

- LMWH is used SC for Tx PE/DVT and ACS (i.e. unstable angina and MI) - it is also used (at a much lower dose) for DVT prophylaxis in a signifcant proportion of inpatient - 3 LMWH: enoxaparin, dalteparin and tinzaparin - you can prescribe LMWH in units or mg - unfractionated heparin is used IV when tighter control is needed (i.e. much less commonly)

Question 35

when to prescribe a lower dose of LMWH?

Answer 35

patients with low body weight or severe renal failure

Question 36

name of Vit K drug?

Answer 36

phytomenadione

Question 37

what to search for INR tables/warfarin?

Answer 37

"oral anticoagulants"

Question 38

Pt with DVT, weight 60 kg, INR 1.0 (<1.4), Tx?

Answer 38

- 1st: LMWH or fondaparinux to patients with confirmed proximal DVT (in/above popliteal) or PE - dalteparin sodium 25 000 units/mL injection - tinzaparin 175 units/kg SC daily - enoxaparin sodium 100 mg/mL injection OR - fondaparinux sodium 12.5 mg/mL injection

Question 39

Enoxaparin/dalteparin/tinzaparin are contraindicated in?

Answer 39

- with current (or history of) heparin-induced thrombocytopenia - high risk of bleeding (e.g. acute gastroduodenal ulcer, cerebral haemorrhage, conditions causing a predisposition to bleed, serious coagulation disorders) - within 3 months stroke (unless due to emboli)

Question 40

LMWHs generally preferred over UF in DVT/PE - EXCEPT when?

Answer 40

- in the case of significant renal impairment | - UF effects are easier to reverse

Question 41

dose of tinzaparin for 60kg patient in DVT Tx?

Answer 41

- tinzaparin sodium 20 000 units/mL injection - 175 units/kg SC daily - 60*175 = 10500 - but can only be given in increments of 0.05ml which is 1000 units - therefore 11 000 units is practical for administration

Question 42

dose of dalteparin for 60kg patient for DVT Tx?

Answer 42

- dalteparin sodium 25 000 units/mL injection | - 12 500 units for a patient weighing 57-68 kg SC daily (0.5 mL) using the 25 000 units/mL strength

Question 43

fondaparinux dose for 60kg patient in DVT Tx?

Answer 43

- fondaparinux sodium 12.5 mg/mL injection - body weight 50–100 kg — 7.5 mg every 24 hours - 7.5 mg SC daily (0.6 mL) using the 12.5 mg/mL preparation

Question 44

how does fondaparinux work?

Answer 44

synthetic pentasaccharide that inhibits activated factor X it is given S/C in a dose based on weight

Question 45

enoxaparin dose for 60kg adult in DVT Tx?

Answer 45

- enoxaparin sodium 100 mg/mL injection - 1.5 mg/kg SC daily - 60*1.5 = 90 mg - 0.9 mL of the 100 mg/mL injection

Question 46

Tx heparin OD?

Answer 46

Protamine sulphate