haemostasis Flashcards
haemostatic mechanisms
platelet plug
vasoconstriction
coagulation
thrombin converts..
fibringogen into fibrin
Why does bernard-soulier syndrome cause bleeding?
platelets do not adhere
clotting factor activation dependent on
carboxylation of glutamate
factor 5 Leiden mutation causes what genetic disorder?
hypercoagulability disorder
vitamin K reduction required for activation of which enzyme?
gamma glutamyl carboxylase
reduced vitamin K acts as a …?
co factor
why are newborns injected with vitamin K
cannot synthesize K2
why can bile acids not be taken with anti-coagulants?
bile acids needed for vitamin K absorption
hemorrhage
warfarin background:
oral
derived from coumarin
delayed onset
long half life
narrow therapeutic range
how does warfarin lower hydroquonione ?
inhibits VKORC1 which converts expoxide into quinione and then to hydroquinione
warfain uses:
DVT and pulmonary emvolism
how does warfarin reduce the availability of hydroquinione
similar structure to vitamin K competitive inhibition of VKORC1
at which level does warfarin cause inhibiton?
inhibits vitamin K epoxide reductase
heparin enhances the activity of which molecule….
antithrombin
by enhancing the effect of antithrombin, which molecules are inhibited by heparin?
clotting factor 10a
thrombin
limitation of heparin:
no effect on thrombus-bound thrombin
half life of heparin vs warfarin
heparin shorter half life
heparin can cause a decrease in circulating….
platelet numbers
types of direct thrombin inhibitors:
bivalent and univalent
DTIS inhibit…
coagulation and platelet activation
warfarin and heparin differ to direct thrombin inhibitors in what way?
direct thrombin inhibitors do not have an active site
downside of rivaroxban:
expensive
effect of antiplatelet drugs:
decrease platelet activation and thrombus formation
difference between arterial and venous thrombi:
platelets in a fibrin mesh are found in arterial circulation
which drugs have anti-platlelet properties?
NSAIDS and SSRIs
3 classes of antiplatlet drugs:
COX1 inhibitors
ADP receptor antagonists
glycoprotein IIb-IIIa antagonists
thromboxane 2 role…
enhances platelet activation
arachidonic acid is the precusor of what molecule….
prostaglandins via COX enzymes
thromboxane is derived from what molecule?
prostaglandin
aspirin inhibits the production of what thromboxane precursor?
prostaglandins
thromboylsis definition
drug induced clot breakdown
what processes do thrombolytic agents enhance?
fibrinolysis via stimulating plasmin production
what is the only drug which breaks down clots?
thrombolytic agents
function of antifibrinlytic agents
reduce the conversion of plasminogen to plasmin
how do bivalent and univalent direct thrombin inhibitors differ?
bivalent bind to two active sites
