Anticoagulation

Question 1

How is unfractionated heparin monitored?

Answer 1

APTT

Question 2

How are LMWH monitored?

Answer 2

anti-Xa assay

Question 3

Effects of enzyme inducers on INR in a patient taking warfarin?

Answer 3

Increase warfarin metabolism and decrease INR

Question 4

Effects of enzyme inhibitors on INR in a patient taking warfarin?

Answer 4

Decrease warfarin metabolism and increases INR

Question 5

Name the enzyme inducers that can decrease drug concentration/INR

Answer 5

antiepileptics: phenytoin, carbamazepine

barbiturates: phenobarbitone

rifampicin

St John’s Wort

chronic alcohol intake
griseofulvin
smoking (affects CYP1A2, reason why smokers require more aminophylline)

Question 6

Enzyme inhibitors that increase drug concentration and increase INR?

Answer 6

antibiotics: ciprofloxacin, clarithromycine/erythromycin MACROLIDES
isoniazid
cimetidine, omeprazole
amiodarone
allopurinol
imidazoles: ketoconazole, fluconazole
SSRIs: fluoxetine, sertraline
ritonavir
sodium valproate
acute alcohol intake
quinupristin

Question 7

Management of warfarin with high INR - major haemorrhage e.g. intracranial bleed, variceal haemorrhage

Answer 7

1. Stop warfarin
2. IV vitamin K 5mg
3. Prothrombin complex concentrate

Question 8

Management if INR > 8 and minor bleeding

Answer 8

1. Stop warfarin
2. IV vitamin K 1-3mg
3. Repeat dose of vitamin K if INR still high after 24 hours
4. Restart warfarin when INR <5

Question 9

Management if INR 8 with no bleeding

Answer 9

1. Stop warfarin
2. ORAL vitamin K (take the IV form orally)
3. Repeat dose of vitamin K if INR still to high after 24 hours
4. Restart when INR <5

Question 10

INR 5-8 with minor bleeding

Answer 10

stop warfarin
give IV vitamin K 1-3mg
restart when INR <5

Question 11

INR 5-8 no bleeding

Answer 11

withhold 1 or 2 doses of warfarin
reduce subsequent maintenance dose

Question 12

Which factors does warfarin affect

Answer 12

II, VII, IX, X

Question 13

clotting screen for someone taking warfarin

Answer 13

prolonged PT, normal APTT