Anticoagulant and Fibrinolytic Drugs Nov21 M2 Flashcards
goal of these drugs
prevent thromboembolism
3 steps of normal coagulation
- retraction of vessel
- platelets activation after factor exposure from endothelium
- coagulation cascade
white vs red thrombus
white in arterial blood
red in venous blood bc stasis, slow flow. more blood stuck in fibrin
normal procoagulant vs anticoagulant factors present
pro: platelet adhesion, aggregation. fibrin clot formation
anti: fibrinolysis + natural inhibitors of coagulation
anticoagulant drugs discussed
UF heparin, LMWH heparin, oral anticoagulants (warfarin, dabigatran, rivaroxaban, apixaban)
fibrinolytic drugs discussed
alteplase (tissue plasminogen activator, a tPA), tenecteplase
heparin descript
sulphated mucopolysacch occuring in mast cells
heparin normal fct
cofactor of antithrombin III
antithrombin III functions (3)
inhibits thrombin (IIa) and factor Xa traps other coag factors, other proteases (suicide substrate)
how express UF heparin dose
USP units
heparin administration and why
IV or subcutaneous (latter = 1-2hr effect delay)
can’t GI bc mast cells destroy it
how heparin degraded
macrophages. reticulo-endothelial system
how monitor heparin dose
with activated partial thromboplastin time (aPTT)
normal aPTT value
30-50 seconds
uses of IV UF heparin
hospital. PE after DVT. DVT above knee joint. unstable angina. MI.
uses of subcut UF heparin
bed-ridden or hosp patients not receiving IV heparin for prevention of DVT
important UF heparin toxicities
- bleeding
- thrombocytopenia
- allergies
why thrombocytopenia possible in UF heparin
transient + harmless in 25% of patients
5% get heparin-induced-anti-platelet antibodies (HIT) can lead to serious bleeding: emergency, can give paradoxical clotting
contraindications of heparin
thrombocytopenia, bleeding disorders, active peptic ulcer disease, severe htn
UF heparin antagonist and when
protamine sulfate. when severe bleeding only. (binds to heparin tightly and inactivates it)
LMWH 2 examples
enoxaparin, dalteparin
LMWH effect compared to UF heparin
On Xa but not IIa. LMWH catalyze Xa inhib by antithrombin III but not IIa (thrombin) inhibition
why LMWH can’t inhib IIa too
lacks tail to bind to IIa too when it’s bound to antithrombin III
LMW vs UF heparin effectiveness
same
LMWH monitoring
none
LMWH effect on aPTT
increased
LMWH something better than UF heparin
less incidence of HIT
LMWH antagonist
not really. (partial effect only from protamine sulfate)
new heparin replacement
fondaparinux (indirect inhibitors of Xa through antithrombin III)
fondaparinux: admin, monitoring, HIT risk
s.c once a day, no monitoring, no HIT risk
fondaparinux problem
no antagonist
2 members of warfarin family
Coumadin (warfarin), sintrom (acenocoumarol)(more in Europe but same)
Warfarin and acenocoumarol fct
antagonizes vitamin K and affects synthesis of factors where it is involved
factors affected by warfarin and sintrom
II, X, IX, VII
warfarin vs heparin: which crosses placenta
warfarin
warfarin monitoring how
prothrombin time (PT), now INR
INR therapeutic level and why boundaries
2 to 3. minimal therapeutic effect but don’T want bleeding
warfarin best for what
prevent stroke in patients with prosthetic heart valves or mitral stenosis
2 other uses of warfarin (less now)
prevent DVT above knee + PE complication AFTER HEPARIN TREATMENT
prevent stroke if a fib
warfarin major toxicity + cause + other toxicity
bleeding. drug interactions. can cross plancenta too
warfarin antagonist (how to treat bleeding)
plasma + concentrated K1
what type of conditions interact dangeroulsy with warfarin
- bad uptake or metabo of vitK or warfarin
- bad synth, fct, clearance of clotting, hemostasis, fibrinolysis factors
- bad integrity of epithelia
most used new oral anticoag
rivaroxaban
dabigatran effect
direct thrombin inhibitor
dabigatran used in what
- prevent stroke in non-valvular a fib
- prev or treat PE after DVP AFTER OR WITH heparin or LMWH
- PE after hip knww replacement
dabigatran
inhibitor + fct
idarucizumab, (humanized monoclonal Ab)
rivaroxaban effect
direct Xa inhibitor
rivaroxaban use
- prev or treat PE, DVT
- prevent stroke in a fib
- after knee hip replacement
new rivaroxaban findings in coronary disease
low dose rivaroxaban + aspirin useful in coronary disease
which new anticoagulants don’t need start on heparin
rivaroxaban and apixaban
apixaban fct
Xa inhibitor
edoxaban fct + something to note
like rivaroxaban (Xa inhibitor) but need to start on heparin
problem with direct factor Xa inhibitors
no antagonist for now
antagonist in dev for Xa inhibitors
Andexanet alfa
fibrinolytic drugs effect and why good and bad
catalyse plasmin formation from plasminogen, to lead to lysis of thrombi
fibrinolytic drugs main use
acute MI with ST elevation in 6 hrs after infarction if PCI not available
danger of fibrinolytic
can lyse physiological thrombi. systemic lytic state