Anticoagulant drugs Flashcards
indications for anticoagulant drugs
VTE recurrent
AF
valve replacement
action of heparin
potentiates antithrombin by making the antithrombin-thrombin complex stronger
also acts on factor Xa
what are the 2 types of heparin
unfractionated
low molecular weight
when is heparin used
acute VTE (DVT, PE)
route for heparin
IV/SC
what does unfractionated mostly affect
thrombin
what does LMW mostly affect
factor Xa
what type of heparin requires monitoring
unfractionated
how is unfractionated heparin monitored
APTT
how often does APTT need to be checked in unfractionated heparin use
every 4-6 hours
why would unfractionated be used over LMWH
risk of bleeding eg GI ulcers
when is heparin used long term
prophylaxis in pregnancy if at high risk
warfarin is contraindicated in pregnancy
complications of heparin
bleeding
thrombocytopenia (monitor FBC, patient collapses within 5-10 days of onset)
osteoporosis if long term
how is heparin reversed
stop heparin (half life of half an hour)
if severe bleeding in heparin therapy, what is management and how effective is it
protamine sulfate
complete reversal if unfractionated
partial reversal if LMWH
what are coumans
warfarin
phenindione
action of warfarin
inhibits vitamin K which is required to decarboxylate factors 2, 7, 9 and 10 to make them active
warfarin keeps them inactive
what else is vitamin K required for
protein C and S function
during initiation of warfarin, what else should be given and why
heparin
proteins C and S are first to be affected by warfarin - become more thrombotic in first few days
when should warfarin be taken
same time every day (6pm I recommended)
what is warfarin metabolised by and why is this important clinically
cytochrome P450b enzymes
antibiotics are also metabolised this way - less warfarin metabolised
higher warfarin conc = higher chance of bleed
how is warfarin monitored and what is the target
using INR
2-3 (higher for mechanical valves)
what are minor bleeds
epistaxis
haematuria
bruising
what are major bleeds
GI bleeds
intracerebral bleeds
if drop in BP
INR 4.5-6 and no bled
reduce warfarin dose
INR 6-8
stop warfarin
resume when <5
INR >8 with no bleed/minor bleed
stop warfarin
give vit K
how long does Vit K take to work
6 hours
if INR >8 and major bleed
stop warfarin
give beriplex (contains clotting factors)
Vit K
fresh frozen plasma if required
how often is INR checked
every day on initiation
then alternative days
then weekly
signs of warfarin toxicity/overdose (SAFETY NETTING)
blood in stool haemoptysis heavy periods blood in urine hameatemasis/abdo pain purpura/bruising bleeding from cuts nose bleeds swollen joints/joint pain dizziness vision changes
how are patients bleeding risk assessed
HASBLED score H - hypertension >160 A - abnormal renal or liver function S - stroke history B - bleeding disposition L - labile INR E - elderly D - drinks >8 alcohol drinks /week, other antibleeding drugs >3 points = high risk of bleeding
example of thrombin inhibitor
dabigatran
examples of factor Xa inhibitors
rivaroxaban
apixapan
advantages of new anticoagulants
oral
no monitoring required
less drug interactions
disadvantage with new anticoagulants
no antidote
