Anticoagulant, Antiplatelet and Thrombolytic Drugs Flashcards
Describe the process of Haemostasis
vascular wall damage exposes collagen and tissue factor
primary haemostasis causes local vasoconstriction platelet adhesion activation and aggregation via fibrinogen
activation of blood clotting( coagulation) to form a stable clot by fibrin enmeshing platelets
d: haemostasis
arrest of blood loss from a damaged vessel
physiological
What is thrombosis?
pathological haemostasis
d: thrombosis
haematological plug in the absence of bleeding
Name the 3 predisposing factors that lead to thrombosis and what they are called collectively?
injury to vessel wall
abnormal BF
coagulability
Virchow’s Triad
What colour is an arterial thrombus?
white
what is an arterial thrombus treated with?
anti-platelets primarily
What is a venous thrombus treated with?
anticoagulants
What colour is a venous thrombus?
red
What are anticoagulants mainly used for?
prevention and treatment of venous thrombosis and embolism
Name the main Anticoagulant drugs
Warfarin
Heparin
Orally active Inhibitors
What receptors does ADP bind to in Primary Haemostasis?
GPCR PURINE receptors
How does warfarin work as an anticoagulant?
competes with vit K
this renders clotting factors II,VII,IX and X inactive
where do arterial thrombus normally lodge?
left heart, carotid artery, brain
where does venous thrombus normally lodge as an embolism/
lungs
How is warfarin taken and it has a fast/slow onset of action?
orally
slow
What is a risk of all anticoagulants?
haemorrhage
do anticoagulants have a low/high therapeutic index? what does this mean?
low
therefore not that safe
what is INR?
internalized normal ratio
used to check how fast blood is clotting under warfarin
How is a warfarin overdose treated?
vitamin K
concentrate of plasma clotting factors
How does Heparin work?
binds to anti-thrombin iii (inhibitor of coagulation) they inhibit factor Xa by binding to ATIII and Xa at the same time.
How is Heparin administered?
either IV -immediate
or SC-delayed an hour
What are some adverse effects of heparin?
haemorrhage
osteoporosis
hyperaldosteronism
hypersensitivity reaction
What type of Heparins are preferred, why?
Low molecular weight Heparins
What type of Heparins are preferred, why? How are they given?
Low molecular weight Heparins
inhibit factor Xa, but not thrombin (IIa)
SC
When are LMWH not preferred?
renal failure
Name 2 orally active inhibitors
Dabigatran
Rivaroxaban
What does Dabigatran do?
direct inhibitor of thrombin
What does Rivaroxaban do?
direct inhibitor of factor of Xa
Name the 2 key antiplatelet drugs
Aspirin
Clopidogrel
How does aspirin work?
irreversibly blocks COX in platelets, preventing TXA2 synthesis
TXA 2 is responsible for activation of platelets
How is aspirin given?
orally as thromboprophylaxis
side effects of aspirin?
GI bleeding and ulceration
How does Clopidogrel work?
inhibits P2Y12 receptor
Blocks binding of ATP to P2Y12 receptor which causes activation of platelets resulting in o fibril linking
How is Clopidogrel given?
orally synergistic with aspirin
What do the drugs that are fibrinolytics do?
used to reopen occluded arteries in acute MI or stroke but prefer PCI
What is PCI?
percutaneous Coronary Intervention
Name some fibrinolytics
streptokinase
alteplase and duteplase
How does streptokinase work? And what is it?
protein extracted from cultures of streptococci
What drug do you use for rapid anticoagulation?
warfarin and heparin together
What drug do you use for less serious anticoagulation?
warfarin
After 4 days of streptokinase why cant further doses not be given?
action blocked after 4 days by the generation of antibodies
What does streptokinase do?
reduces mortality in MI but cation blocked after 4 days
How does streptokinase work?
activates plasminogen
plasmin which breaks down the fibrin down to fragments lysing the clot
side effects of Streptokinase?
may cause allergic reactions
and cant be used after 4 days
How do alteplase and duteplase work?
Are recombinant tissue plasminogen activator (rt-PA)
Why are alteplase and duteplase more effective on fibrin bound plasminogen than plasma plasminogen?
show selectivity for clots
no allergic reactions
How Alteplase and duteplase given? Why?
IV
short half life
Name the major adverse affects of fibrinolytics?
haemorrhage which may be controlled by oral tranexamic acid which inhibits plasminogen activation
