Anti-Coagulant Drugs Flashcards
what are two indications for anticoagulants?
venous thrombosis
AF - stroke prevention
what do anticoagulant drugs target?
the formation of the fibrin clot
name three types of anti coagulant
heparin
warfarin
DOACs
how does heparin work?
potentiates the naturally occurring anti-coagulant, anti thrombin
how long does it take for heparin to have an effect?
immediate
what are the two possible routes of administration of heparin?
IV
SC
what are the two forms of heparin?
unfractionated
low molecular weight (LMWH)
what is the MoA of unfractionated heparin?
binds to the complex of anti-thrombin and thrombin, keeping it together and stabilising it = more clot breakdown
what is the MoA of LMWH?
binds to anti-thrombin bound to factor Xa to prevent it from being deactivated
which type of heparin requires close monitoring due to its less predictable responses?
unfractionated
which type of heparin can be given at fixed doses?
LMWH
what effect does heparin have on coagulation screen results?
PT and APTT will be prolonged
what should be monitored when giving unfractionated heparin?
APTT
what can be monitored to assess LMWH in complex patients?
anti-Xa assay
not usually needed
what is the main risk of heparin use?
bleeding
what is a possible rare complication of heparin?
heparin induced thrombocytopenia with thrombosis (HITT)
what should be monitored in patients on heparin in case of HITT?
FBC
what causes HITT with heparin use?
when heparin results in antibody formation
what complication can be caused by long term heparin use?
osteoporosis
what can be done to reverse heparin in most cases and why?
stop giving it
very short half life
what can be given to reverse heparin in severe bleeding?
protamine sulphate
complete reversal for unfractionated, partial for LMWH
name four coumarin anticoagulants
warfarin
phenindione
acenocoumarin
phenprocoumon
what is the MoA of warfarin?
inhibition of vitamin K leading to the synthesis of non functional coagulation factors
what are the vitamin K dependent proteins involbed in haemostasis?
factors 2,7,9 and 10
protein C and S
what should be given when starting on warfarin and why?
heparin
initially increased risk of clots due to lack of protein C and S, goes away after around 5 days
when should patients take warfarin?
at the same time everyday
how is warfarin response monitored?
INR
what is the target INR for most patients on warfarin?
2-3
what does a higher INR suggest?
less likely to thrombose, more likely to bleed
what can be done to reverse warfarin if there is minor bleeding, to bring INR down over a few days?
omit warfarin doses
what should be done to reverse warfarin if INR>8?
administer oral vitamin K
how long does it take for oral vitamin K to reverse warfarin?
around six hours
what should be given for immediate reversal of warfarin in severe bleeding?
clotting factor concentrates
what are the two types of DOACs?
oral direct thrombin inhibitors
oral Xa inhibitors
what monitoring is required for DOACs?
none
name an oral direct thrombin inhibitor
dabigatran
how do oral direct thrombin inhibitors work?
target thrombin, preventing the fibrin clot from forming
also prevent factors 8+9 being activated
when are direct thrombin inhibitors contraindicated and why?
patients with renal problems as they are renally excreted
which type of DOAC is more commonly used?
oral Xa inhibitors
how do oral Xa inhibitors work?
directly inhibit Xa
name three oral Xa inhibitors
edoxaban
rivaroxaban
apixaban
