Anticoagulants Flashcards
What are the two main indications for anticoagulants?
Treatment - vte (DVT/PE)
Prophylaxis - vte (DVT/PE/stroke)
Describe how low molecular weight heparin works?
Factor Xa inhibitor
How often is LMWH given and by what route?
OD/BD
SC
Is monitoring required for LMWH?
no
Only in special situations check activated factor X levels
What should you do to the dose of LMWH in renal failure?
Reduce if for prophylaxis
How is unfractionated heparin given?
IV/SC
Describe how unfractionated heparin works?
Binds to antithrombin III (endogenous inhibitor of coagulation). Increases its ability to inhibit thrombin, factor Xa and IXa
Describe the speed of onset of unfractionated heparin
Fast onset
How is unfractionated heparin monitored and dosed?
APTT
List the side effects of both LMWH and UFH
Increased bleeding
Heparin induced thrombocytopenia (HIT)
Osteoporosis with long term use (less common in LMWH than UFH)
Hyperkalaemia
Which side effects are less common in LMWH than UFH
HIT and osteoporosis
What are the contraindications to heparins
Bleeding disorders Platelets <60X10^9 Previous HIT Peptic ulcer Cerebral haemorrhage Neurosurgery Severe hypertension
Name some low molecular weight heparins
Dalteparin
Enoxaparin
Tinzaparin
Describe the mechanism of action of warfarin
Inhibits the reductase enzyme and stops vitamin K being activated - creates a similar state to vit K deficiency
Describe the therapeutic range of warfarin
Narrow
List the CI of warfarin
Peptic ulcer, severe HTN, pregnancy, bleeding disorders
How is warfarin taken?
PO OD
What is warfarin used for?
Long term anticoagulation
When should warfarin be used with caution?
Elderly and those with past GI bleeds
Give the doses and colours of warfarin tablets
White = 0.5mg Brown = 1mg Blue = 3mg Pink = 5mg
Name some drugs which increase activity of warfarin
Alcohol Allopurinol Amiodarone Levothyroxine Phenytoin Aspirin Chloramphenicol Simvastatin Ciprofloxacin Erythromycin
Name some drugs which decrease the activity of warfarin
Barbiturates Vitamin K Carbamazepine Rifampicin Steroids
Name some direct oral anticoagulants
Rivaroxaban
Apixaban
Dabigatran
Give the mechanism of action for dabigatran
Direct thrombin inhibitor (II)
Give the mechanism of action for rivaroxaban and apixaban
Factor Xa inhibitors
Do DOACs require any monitoring?
No - just quarterly assessment and annual blood test
List the CI to DOACs
Active bleeding
Lesion at risk of bleeding
Decreased clotting factors
Which two drugs interact with DOACs
Heparin
Clopidogrel
Give the mechanism of action of fondaparinux
Penta saccharide Xa inhibitor
When may fondaparinux be used?
ACS or in place of LMWH for prophylaxis
Describe how you switch between LMW/UFH to warfarin
Give heparin in combination and continue until INR is in therapeutic range for 2 consecutive days
Start warfarin 5-10mg on days 1 and 2 at 18.00, then check INR on day 3 (takes 48-72hrs to work)
Adjust dose according to INR
Measure INR in alternate days till stable, then weekly, then less often
Describe how you transition from heparin to a DOAC
Do not administer heparin with a DOAC
Just switch
Describe how you manage a UFH overdose?
Stop infusion
What should you give someone with an UFH overdose who is bleeding
Protamine sulphate
Name two things which can be used to reverse warfarin
Vitamin K (but takes ages to work) Prothrombin complex concentrate
What is contained in a prothrombin complex concentrate
Factors 2,7,9,10
Give the targeted INRs
2-3 if DVT/PE
3.5 if recurrent or while anticoagulated
2-3 if AF
2-3.5 if prosthetic metal valve
How long should someone be anticoagulated for after 1st episode of VTE
3 months or 6 months if life threatening clot at presentation and those with transient but persistent RF
How long should a person be anticoagulated for if recurrent unprovoked emboli or underlying thrombophilia?
Indefinite treatment but consider bleeding risk
How long before surgery should warfarin be stopped?
5 days
How does warfarin affect PT and APTT?
Increased PT
Normal APTT
At what INR should warfarin be restarted after being stopped due to bleeding?
<5
