DOACs Flashcards
use of anticoagulants
prevent thrombus formation or extension of existing thrombus in slower-moving venous side of circulation, where thrombus consists of fibrin web enmeshed with platelets and red cells
Vitamin K anatgonists
~ warfarin, acenocoumarol, phenindione
~ antagonise effects of vitamin K,
~ take at least 48 to 72 hours for anticoagulant effect to develop fully; warfarin sodium = drug of choice. If immediate effect required, unfractionated or LMW heparin must be given concomitantly.
~ should not be used in cerebral artery thrombosis or peripheral artery occlusion as 1st-line therapy; aspirin more appropriate for reduction of risk in TIA. Unfractionated or low LMW usually preferred for prophylaxis of VTE in patients undergoing surgery; alternatively, warfarin sodium can be continued in selected patients currently taking long-term warfarin sodium and at high risk of thromboembolism
INR within … of target value generally satisfactory; larger deviations require dosage adjustment
0.5 units
INR 2.5 for
~ TX of DVT or PE
~ Atrial fibrillation
~ Cardioversion—target INR achieved at least 3 weeks before cardioversion & continue for at least 4 weeks after procedure (higher target values, INR of 3, used for up to 4 weeks before procedure to avoid cancellations due to low INR)
~ dilated cardiomyopathy
mitral stenosis or regurgitation in patients with either atrial fibrillation, Hx of systemic embolism, a left atrial thrombus, or enlarged left atrium
bioprosthetic heart valves in the mitral position (treat for 3 months), or in patients with history of systemic embolism (treat for at least 3 months), or with left atrial thrombus at surgery (treat until clot resolves), or with other risk factors (e.g. atrial fibrillation or low ventricular ejection fraction).
~ acute arterial embolism requiring embolectomy
~ myocardial infarction
INR 3.5 for
~ recurrent DVT or PE in patients currently receiving anticoagulation & with INR above 2;
~ Mechanical prosthetic heart valves:
Warfarin & MAJOR BLEEDING
STOP warfarin sodium
~ give phytomenadione (vitamin K1) by slow intravenous injection
~ give dried prothrombin complex (factors II, VII, IX, and X)
~ if dried prothrombin complex unavailable, fresh frozen plasma given but less effective; recombinant factor VIIa not recommended for emergency anticoagulation reversal
Warfarin and INR >8.0, minor bleeding—
~ STOP warfarin sodium
~ give phytomenadione (vitamin K1) by slow intravenous injection
~ repeat dose of phytomenadione if INR still too high after 24 hours
~ restart warfarin sodium when INR <5.0
Warfarin & INR >8.0, no bleeding—
~ STOP warfarin sodium
~ give phytomenadione (vitamin K1) by mouth using intravenous preparation orally [unlicensed use]
~ repeat dose of phytomenadione if INR still too high after 24 hours
~ restart warfarin when INR <5.0
Warfarin & INR 5.0–8.0, minor bleeding
~ STOP warfarin sodium
~ give phytomenadione (vitamin K1) by slow intravenous injection
~ restart warfarin sodium when INR <5.0
Warfarin and INR 5.0–8.0, no bleeding
withhold 1 or 2 doses of warfarin sodium & reduce subsequent maintenance dose
Peri-operative anticoagulation
Warfarin usually stopped 5 days before elective surgery
~ phytomenadione (vitamin K1) by mouth (using intravenous preparation orally [unlicensed use]) given day before surgery if INR ≥1.5. If haemostasis adequate, warfarin sodium can be resumed at normal maintenance dose on evening of surgery or next day.
Patients stopping warfarin sodium prior to surgery who are considered to be at high risk of thromboembolism (e.g. those with a venous thromboembolic event within the last 3 months, atrial fibrillation with previous stroke or transient ischaemic attack, or mitral mechanical heart valve) may require interim therapy (‘bridging’) with a low molecular weight heparin (using treatment dose). The low molecular weight heparin should be stopped at least 24 hours before surgery; if the surgery carries a high risk of bleeding, the low molecular weight heparin should not be restarted until at least 48 hours after surgery.
Patients on warfarin sodium who require emergency surgery that can be delayed for 6–12 hours can be given intravenous phytomenadione (vitamin K1) to reverse the anticoagulant effect. If surgery cannot be delayed, dried prothrombin complex can be given in addition to intravenous phytomenadione (vitamin K1) and the INR checked before surgery.
Combined anticoagulant and antiplatelet therapy
Existing antiplatelet therapy following ACS or percutaneous coronary intervention continued for the necessary duration according to indication being treated. The addition of warfarin sodium, when indicated (e.g. for venous thromboembolism or atrial fibrillation) should be considered following an assessment of the patient’s risk of bleeding and discussion with a cardiologist. The duration of treatment with dual therapy (e.g. aspirin and warfarin sodium) or triple therapy (e.g. aspirin with clopidogrel and warfarin sodium) should be kept to a minimum where possible. The risk of bleeding with aspirin and warfarin sodium dual therapy is lower than with clopidogrel and warfarin sodium. Depending on the indications being treated and the patient’s risk of thromboembolism, it may be possible to withhold antiplatelet therapy until warfarin sodium therapy is complete, or vice versa (on specialist advice) in order to reduce the length of time on dual or triple therapy.
DOACs
Apixaban, dabigatran, edoxaban, & rivaroxaban
~ reversible inhibitors of activated factor X (factor Xa) to prevents thrombin generation & thrombus development
Dabigatran
reversible inhibitor of free thrombin, fibrin-bound thrombin, & thrombin-induced platelet aggregation
anticoagulant effects of DOACs
diminish 12 to 24 hours after last dose taken, therefore omitted or delayed doses could lead to reduction in anticoagulant effect
Reversal agents for dabigatran
Idarucizumab
Reversal agents of apixaban or rivaroxaban
Andexanet alfa
Reversal agents of Edoxaban
NONE
