Pharm Unit 2 - Anti-Thrombotics Flashcards
antiplatelets
prevent blood clot formation
primary hemostasis
endothelial injury
adhesion
activation
aggregation
endothelial injury
exposure of collagen and vWF inside vessel
adhesion
circulating platelets bind to vWF and collagen
activation
shape change of platelets
TXA2 release
granual release
GP IIb/IIIa conformation change
do platelets have nucleus?
no
TXA2 function
thromboxane recruits more platelets to the plug
expands the clot
what is converted into TXA2
arachadonic acid –> TXA2
what does granule release do
ADP
coagulation factors
aggregation
fibrinogen cross linking between platelets’ surfaces
anti-thombotic therapy goals
prevent thrombosis
without over promotion of bleeding
main risk of antithrombotics
bleeding
increase risk of death 3-5x
pt monitoring during antithrombotic therapy
Hgb drop
bloody stools
melena
hematuria
bruising
oozing from arterial/venous puncture
antiplatelets drug types
aspirin
P2Y12 receptor antagonists
GP IIb/IIIa inhibitors
Vorapaxar
aspirin mechanism
irreversibly inhibits COX-1
prevents conversion of arachidonic acid into thromboxane
- decr platelet formation
- decr vasoconstriction
aspirin uses
prevention of DVT
prevention of ASCVD (secondary)
- MI
- angina
- stroke/TIA
- PAD
- CAD
antiypyretic
analgesic
prevention of colorectal cancer
what is the fastest way to get aspirin into the body?
chew non-enteric coated
–20 mins
duration of aspiring effects
lasts entire platelet lifespan
wears off once new plts are made
aspiring SE
GI
bleeding
allergic rxns
incr hemorrhagic stroke in men
aspiring drug interactions
NSAIDs will blunt aspirins effect
incr risk of serious GI complications
ADP
binds to P2Y1
- incr Ca2+ == shape change
binds to P2Y12
- granule release
both paths activate GPIIb/IIIa, resulting in platelet aggregation
which is the more dominant ADP biding site?
P2Y12
so drugs target P2Y12
P2Y12 ADP inhibitor drugs
clopidogrel
prasugrel
ticagrelor
cangrelor
what polymorphism impacts clopidogrel?
decr CYP2C19 function
loss of effectiveness of drug
clopidogrel and prasugrel bind
irreversibly to P2Y12 receptor
which is more potent: clapidogrel or prasugrel?
prasugrel has more potent plt inhibition w/faster onset
clopidogrel is a prodrug so must be metabolized to work == slower
if you inhibit CYP2C19 function, would you amplify or reduce clopidogrels anti-platelet effect?
reduce
clopidogrel requires CYP2C19 to convert into active form
clopidogrel indications
acute coronary syndrome
- typically DAPT w/aspirin
percutaneous coronary intervention
- prevents stent thrombosis
2ndary prevention in atherothrombotic disease
- CAD
- CVD
- PAD
what drug can replace aspiring in prevention of atherothrombotic disease?
clopidogrel
Prasugrel CI
<60 kg = half dose
Stroke or TIA history
>75 yrs old
cannot be used in CABG pts
Prasugrel indication
only pts w/PCI and stent implant
Ticagrelor and Cangrelor bind
reversibly to ADP P2Y12 receptor
Ticagrelor and Cangrelor are administered
IV only
Ticagrelor: 2x daily
Cangrelor: continous IV
Ticagrelor is metabolized by
CYP3A
Ticagrelor vs Clopidogrel
ticagrelor has:
faster onset
more potent platelet inhibition
What other receptor does Tacagrelor block?
ENT1
– incr adenosine plasma levels
– incr endothelium function
– decr HR
Ticagrelor SE
dyspnea
– P2Y12 incr neuronal signaling
– incr conductivity of pulmomnary vagal C-fibers
– incr sensation of dyspnea
cangrelor bleeding rates compared to clopidogrel
cangrelor has higher bleeding rates compared to clopidogrel
cangrelor SE
dyspnea
decr renal function (3.2%)
Cilostazol mechanism
PDE3 inhibitor
incr intraplatelet cAMP
decr Ca2+
plt inhibition
Cilostazol effects
platelet inhibition
inhibit vascular smooth muscle cell proliferation
improves peripheral BF
Cilostazol indications
PAD - claudication
PVD
stroke/TIA
post-PCI
Cliostazol CI
HF
most abundant receptor on platelates
Gp IIb/IIIa
80,000 copies/plt
GPIIb/IIIa inhibitor mechanism
binds to GPIIb/IIIa receptors
prevents formation of fibrinogen plt-plt crosslinks
GPIIb/IIIa inhibitor indications
PCI
unstable angina
GP IIb/IIIa inhibitors SE
bleeding
thrombocytopenia
GP IIb/IIIa drugs
abcimimab
eptifibatide
tirofiban
GP IIb/IIIa inhibitor CI
active internal bleeding
major surgeries
recent trauma
intracranial hemorrhage
bleeding disorders
severe hypertension
abciximab has a ____ % risk of thrombocytopenia
5% risk
1% severe risk
anticoagulants
prevent blood clots from forming by interfering with coagulation factors
hemostasis
stopping bleeding
primary hemostasis
formation of platelet plug
secondary hemostasis
coagulation
extrinsic pathway of secondary hemostasis
activated by tissue factor found outside the blood
intrinsic pathway of secondary hemostasis
factors required for activation are found in the blood
common pathway
activation of factor X
coagulation cascade
4 parental anticoagulants
unfractionated heparin
low molecular weight heparin
synthetic pentasaccharides
direct thrombin inhibitors
parenteral anticoagulatns indications
DVT
PE
initial management of ACS
clotting times
measure the time it takes plasma to clot when various substances are added
prothrombin time (PT)
assesses extrinsic pathway of coagulation
INR
activated clotting time (ACT)
measures time of clot formation via the intrinsic coagulation pathway
high dose heparin monitoring uses
ACT
activated partial thromboplastin time (aPTT)
assess intrinsic pathway of coagulation
antifactor Xa assay
measures unbound Factor Xa level
assesses functional activity of anticoagulant
unfractionated heparin mechanism
binds to endothelium/plasma proteins
causes a confirmational change in antithrombin
inactivates clotting factor proteases (IIa, IXa, Xa)
which molecular weight heparin inhibits thrombin
High molecular weight heparin inhibits thrombin
heparin clinical uses
PE
DVT
clot prevention in arterial/cardiac surgery
Afib w/embolization
ACS
MI
Low-molecular weight heparin mechanism
primarily inhibit Factor Xa
heparin SE
hemorrhage
heparin induced thrombocytopenia (HIT)
epidural/spinal hematoma
HIT
prothrombotic
Heparin monitoring
aPTT
anti-factor Xa plasma levels
ACT (high doses)
heparin aPTT
2-3x normal
heparin clearance
reticuloendothelial system
dose-dependent
- low = fast clearance
- high = long clearance
heparin reversal
protamine sulfate
protamine sulfate
highly basic (+ charge)
neutralizes heparin
better at HWMH than LWMH
Heparin Induced Thrombocytopenia
antibody mediated process
PF4-heparin antibody rxn
activated plts
decr plt count
incr thrombin production
incr clotting
occurence rate of HIT
5%
HIT ocurrence timeframe
4-10 days post-heparin dosing
LMWH drugs
enoxaparin
dalteparin
tinzaparin
LMWH
longer half life
more predictable
minimal need for monitoring
kidney clearance
decr HIT risk
partial reversal by protamine
Fondaparinux
synthetic indirect Factor Xa inhibitor
100% bioavailability
Fondaparinux mechanism
binds antithrombin
inactivation of factor Xa
Fondaparinux is dependent on
renal excretion
renal impairment (Fondaparinux clearancce rates)
mild: decr clearance 25%
mod: decr clearance 40%
sev: decr clearance 55%
Fondaparinux SE
thrombocytopenia
(2.9%)
severe (0.2%)
hemorrhage
epidural/spinal hematoma
does fondaparinux cause HIT?
no
LMWH/Fondaparinux CI
epidural indwelling catheter
NSAIDs
plt inhibitors
anticoagulants
traumatic epidurals/spinals
spinal deformity
spinal surgery
Direct Thrombin inhibitor mechanismn
directly bind and inhibit unbound and fibrin-bound thrombin
direct thrombin inhibitor drugs
bivalriduin
argatroban
bivalirudin metabolism/excretion
met: blood proteases
excr: urine (20%)
argatroban metabolism
hepatic
bivalirudin requires does adjustment for
renal impairment
CrCl<30
argatroban requires dose adjustment for
hepatic impairment
direct thrombin inhibitor monitoring
aPTT
ACT
argatroban does what to PT and INR
argatroban prolongs PT/INR
argatroban indications
HIT pts
bivalirudin indications
PCI (coronary angioplasty)
with or w/o HIT
direct thrombin inhibitor side effects
hemorrhage
oral anticoagulants
warfarin
dabigatran
direct Factor X inhbitors
– apixaban
– edoxaban
– rivaroxaban
oral anticoagulants indications
DVT
PE
stroke prevention in afib pts
Warfarin mechanism
inhibits conversion of Vit K into its active form
results in incomplete clotting factors that are biologically inactive in coagulation
Active Vit K is needed for
the production of functional clotting factors:
II
VII
IX
X
and anticoagulant proteins:
C
S
what polymorphisms impact warfarin clearance and dosing?
CYP2C9
what polymorphisms impact warfarin anticoagulation response?
VKORC1
which polymorphisms have reduced enzyme activity with warfarin?
CYP2C92
CYP2C93
what polymorphism are associated with increased sensitivity to warfarin and lower dose requirements?
VKORC1
– G3673A
– -1639G>A
VKORC1 G/G warfarin dosing
46 mg/wk
VKORC1 G/A warfarin dosing
33 mg/wk
VKORC1 A/A warfarin dosing
21 mg/wk
when is the anticoagulant effect of warfarin observed?
after elimination of normal pre-formed clotting factors
~48-72 hrs post-administration
how do you recover from warfarin?
synthesize new normal clotting factors
which coagulation factor has the shortest half-life with warfarin?
shortest: F VII
FIX
FX
longest: FII
what is the length of time to maximal effect of warfarin on Factor II?
7 days
warfarin normal INR
2.0-3.0
warfarin starting dose
5mg daily
titrate to appropriate INR
warfarin SE
bleeding
skin necrosis (3-10 days)
thrombosis of microvasculature
protein C depletion
warfarin CI
pregnancy
warfarin reversal
Vit K (phytonadione)
clotting factor replacements to help warfarin reversal
fresh frozen plasma
prothrombin complex concentrate
recombinant factor VIIa
Direct oral anticoagulant drugs
dabigatran
rivaroxaban
apixaban
edoxaban
direct oral anticoagulants inhibit what factors?
Factor Xa
Factor IIa
Factor Xa inhibitors
rivaroxaban
apixaban
edoxaban
Factor IIa inhibitor
dabigatran
DOAC onset
rapid
DOAC dosing
fixed
Do you need to monitor DOACs?
no
dabigatran clearance
renal (80%)
which DOACs are metabolized by the liver?
rivaroxaban
apixaban (minor)
edoxaban (minimal)
dabigatran SE
dyspepsia
DOAC boxed warning
increased rate of stroke following discontinuation of DOACs
(incr risk of thrombotic events)
dagibatran antidote
idarucizumab
(monoclonal antibody)
DOAC antidote
decoy Factor Xa
–decr DOAC effect
DOAC indications
DVT
PE
VTE (hip/knee replacements)
stroke prevention in afib
Rivaroxaban inbdications
chronic CAD or PAD
– combined w/aspirin to decr risk
thrombolytics
break up blood clots formed during hemostasis
restore blood flow
thrombolytics drugs
alteplase
reteplase
tenecteplase
streptokinase
which thrombolytics are derived from tPA
alteplase
reteplase
tenecteplase
streptokinase is derived from
beta hemolytic bacteria proteins
tPA derived-thrombolytics mechanism
bind to fibrin proteins
onverts plasminogen to plasmin
plasmin degrades fibrin mesh
streptokinase mechanism
binds to circulating or fibrin bound plasminogen
converts plasminogen to plasmin
plasmin degrades fibrin mesh
which thrombolytic is not selective to fibrin? what does that mean?
streptokinase
it impacts the entire body, not just fibrin
thrombolytics indications
short term emergent mgmt of thrombosis
STEMI
DVT
PE
acute ischemic stroke
acute peripheral arterial occlusion
thrombolytics SE
severe bleeding
intracranial hemorrhage
thrombolytics CI
active internal bleeding
close to major surgiers
after recent trauma
suspected aortic dissection
intracranial hemorrhage
bleeding disorders
severe hypertension
thrombotic (fibrinolytic) antidotes
aminocaproic acid
tranexamic acid
aminocaproic acid mechanism
blocks binding of plasminogen to fibrin
blocks conversion of plasminogen to plasmin
tranexamic Acid mechanism
forms reversible complex that displaces plasminogen from fibrin
inhibition of fibrinolysis
thrombotic (fibrinolytic) antidote indications
fibrinolytic bleeding
hemophilia
prevention of surgical blood loss
post-trauma hemorrhage