Anticoagulant Drugs Flashcards
what are indications for anticoagulant drugs
venous thrombosis
atrial fibrillation
what is the mechanism of action of heparin and how can it be taken
Potentiates antithrombin
Immediate effect - can be given in acute situations
IV or sc
what are the 2 forms of heparin
unfractionated
LMWH
how does LMWH differ from unfractoinated heparin in terms of mode of action
unfractionated = more suited too Anti Thrombin and thrombin.
LMWH = more suited to Anti Thrombin and factor X
what is used to monitor heparin
APTT
when would more monitoring of a patient on heparin be considered
Hx of kidney disease
- heparin is cleared through the kidneys
what are complications of Heparin
bleeding
Heparin induced thrombocytopenia (with thrombosis) = HITT
osteoporosis
what happens in HITT
can develop anti bodies to heparin»_space;> leading to thrombocytopenia
occurs between 5-10 days of starting heparin
how would you monitor for HITT
need to monitor FBC = if you see platelet count drop between 5-10 days
would need to stop the drug
what is the antidote to heparin
protamine sulphate
what else can be done if you need a heparin reversal
stop heparin
- has a short half life, particularly unfractionated [only 30 mins]
what are features of vitamin K - where is it absorbed
Fat soluble vitamin
Absorbed upper intestine
Requires bile salts for absorption
what is vitamin K needed for
Final carboxylation of clotting factors II, VII, IX and X
Protein C and S
what is first affected when warfarin is given
Protein C and S
- have a much shorter half life than clotting factors
what does vitamin K do
adds COOH group to clotting factors that make it possible for them to bind through calcium to the phospholipid platelet
how does warfarin work
blocking the ability of Vitamin K to carboxylate the Vitamin K dependent clotting factors, thereby reducing their coagulant activity
what is the name for the MOA of warfarin
antagonism of vitamin K
causing synthesis of non functional coag factors
where is warfarin metabolised and what can interfere with this
liver
alcohol metabolised by the same enzyme
what is the INR window we aim for with warfarin treatment
INR 2-3
above = risk of bleeding below = not doing anything useful
what is INR
standardisation of PT across labs
what are complications of warfarin
Haemorrhaging
- beware drug interactions
what are bleeding complications seen in warfarin therapy
mild
- skin bruising, epistaxis, haematuria
severe
- GI, intracerebral
- would see significant drop in Hb
how can warfarin actions be reversed
1-2mg oral vitamin K
- reveres affects in 6 hours
IV clotting factors
- reveres affects immediately
what are new anti-coagulants
Thrombin inhibitors
- e.g. Dabigatran
Xa inhibitors
- e.g. Rivaroxaban, Apixaban
what is Rivaroxaban starting to be used first line in
AF
DVT, PE
why are new anticoagulants starting to be preferred
taken orally
no monitoring required
less drug interactions
how can warfarin be taken
IV or oral
what are drawbacks of the new anticoagulants
no specific antidote
