B3.087 - Anticoagulant Therapies COPY Flashcards
why do clots form
- turbulence in blood flow
- abnormalities of surface in contact with blood
- abnormalities in clotting factors
what are conditions with abnormal clotting factors
Protein C deficiency
Protein S deficiency
Antithrombin III deficiency
antiphospholipid antibody syndrome
what are the general classes of drugs that treat hemostasis disorders
platelet inhibitors
anticoagulants
thrombolytic drugs
Drugs for bleeding disorders
what do TxA2 and ADP do in primary hemostasis
platelet granule release reaction
what are the antiplatelet drugs
Abciximab Tirofiban Aspririn Ticlopidine Clopidogrel
what is acetylsalicylic acid
aspirin
what does aspirin do
inhibits synthesis of thromboxane A2 by irreversible acetylation of cyclooxygenase COX 1 in platelets
what does thromboxane A2 do
potent mediator of platelet aggregation and degranulation and promotes vasoconstriction
what is aspirin used for
prevents and reduces risk of MI and recurring transient ischemic attacks
how does aspirin work
irreversibly inactivates COX-1; TXA2 end product causes platelet activation and vasoconstriction which is prevented here
what does COX2 do
is in endothelial cells and is inhibited by aspirin and by COX 2 inhibitors; PGI2 causes platelet inhibition and vasodilation
when do you see effects of aspirin
1-2 days after administration and lasts the duration of the platelet life span (7-10 days)
why does wiping out the COX1 affect platelets more than other cell types
they have no nucleus so they cant make new proteins in response, so the effects are seen until the platelets die and are replaced
what type of drug is ticlopidine and how does it work
ADP antagonist, inhibits ADP receptors on platelets which prevents activation of GPIIb-IIIa
what is ticlopidine indicated for
alternative to aspirin to prevent an initial or recurrent thromboembolic stroke and MI thromboembolic stroke
how is ticlopidine administered
orally, bioavailability 80%
adverse effects of ticlopidine
nausea, dyspepsia, diarrhea in 20% of patients, hemorrhage in 5%
what is ticlopidine associated with (AEs that are more severe)
TTP (thrombotic thrombocytopenia purpura)
Severe bone marrow toxicity
what does clopidogrel do
similar mechanism to ticlopidine (ADP antagonist) but lower incidence of adverse effects
what is clopidogrel used for
patients with a history of recent stroke, MI or established peripheral vascular disease, pts with stents
what is an important AE of clopidogrel
many drug drug interactions because requires activation by CYP2C9
what are other drugs metabolized by 2C9 and what drug can cause interactions with these
Clopidogrel causes interactions Fluvastatin NSAIDs Phenytoin tamoxifen tolbutmide warfarin
when would ticlodipine be preferred over clopidogrel
if drug drug interactions are difficult to manage
where is clopidogrel metabolized
liver
how does abciximab work
inhibits platelet aggregation by preventing binding of fibrinogen to glycoprotein receptor IIb/IIIa on activated platelets
how is abciximab administered
IV to high risk pts undergoing coronary angioplasty and pts undergoing angioplasty, atherectomy and stent placement often with clopidogrel
downsides to Abciximab including AEs
Expensive
Bleeding most common AE
what does Tirofiban do
small molecule that with short half life that works similar to Abciximab, has to be continually infused bc of short half life
How does dipyridamole work
inhibits phosphodiesterase which leads to increased cAMP levels, inhibiting platelet activation
what does phosphodiesterase do normally
breaks down cAMP
what effects does dipyridamole do
coronary vasodilator that also inhibits platelet aggregation
what is dipyridamole used for
in combo with warfarin, inhibits embolism from prosthetic heart valves (main use)`
what is dipyridamole combined with aspirin to treat
patients with thrombotic disease, reduces thrombosis
what do calcium chelators do
inhibit blood coagulation in vitro
what do heparins do
accelerate the action of antithrombin III to neutralize thrombin and other coagulation factors
what do rudins do
direct thrombin inhibitors
what do coumarin derivatives do
interfere with the hepatic synthesis of functional vitamin K dependent clotting factors
what are calcium chelators used for and why cant you use them in the body
for lab draws to prevent coagulation
cant use them in the body because calcium is used on so many function
structure of standard heparin
sulfated mucopolysaccharide (acidic molecule)
route of admin for standard heparin
NOT ORAL OR IM
infusion pump or intermittent Subcutaneous
onset of action of standard heparin
immediate
mechanism of action of standard heparin
heparin binds to antithrombin III and stimulates complex formation with antithrombin III
Main mech is heparin-antithrombin III complex inactivates factor IIa (thrombin) and Xa
heparin AEs
endothelial cell/protein binding
Clearance is dose dependent
therapeutic goal of standard heparin
prolong PTT to 1.5-2.5x normal
contraindications of standard heparin
bleeding disorders, hemorrhage
liver, kidney disease, HT, certain infections