Drugs for Thromboembolic Disorders (Wolff) Flashcards
White (platelet-rich) thrombi form in arteries under what type of pressure?
High-pressure arteries
What are 2 pathologic conditions of coronoary arteries associated w/ white thrombi?
- MI
- Unstable angina
Red (fibrin-rich) thrombi form in vessels under what type of pressure and in which location?
Low-pressure veins and in the heart
Anticoagulants are primarily used to prevent clots form forming where?
Which specific type of thrombi?
- Venous system and heart
- Red (fibrin) thrombi
Antiplatelet drugs are primarily used to preven clots from forming in which vessels?
What specific type of thrombi?
- Arteries
- White thrombi
What are the 3 classes and drugs in each of parenteral anticoagulants which act as indirect thrombin and factor Xa (FXa) inhibitors?
- Unfractionated (HMW) heparin = Heparin sodium
- LMW heparins = Enoxaparin, Tinzaparin, and Dalteparin
- Synthetic pentasaccharide = Fondaparinux
Which 3 drugs belong to the direct thrombin inhibitor class and are used as parenteral anticoagulants?
- Lepirudin
- Argatroban
- Bivalirudin
The indirect thrombin and factor Xa (FXa) inhibitors bind to what in the plasma?
Serine protease inhibitor antithrombin III
Unfractionated (HMW) heparin inhibits the activity of?
Thrombin and factor Xa
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LMW heparins inhibit what?
Factor Xa w/ little effect on thrombin
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Which 2 drugs in the parenteral direct thrombin inhibitor class are bivalent and bind at both the active site and substrate recognition site of thrombin?
- Lepirudin
- Bivalirudin
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Which parenteral class of heparin has increased bioavailability from the SC injection site and allows for less frequent injections and more predictable dosing?
LMW Heparin (-aparin’s)
Heparins are used during surgery or in hospitalized patients to reduce the risk of what?
Reduces risk of emboli
Heparin is administered to patients with what disorders?
- DVT
- Atrial arrhythmias
Why must heparins be given via IV or SC routes?
Very hydrophilic
What are 2 AE’s associated with Heparin?
- Bleeding
- Heparin-induced thrombocytopenia (HIT)
What are heparin locks used for?
Prevents clots from forming in catheters
What 2 lab studies are used to monitor patients on Heparin?
- Activated partial thromboplastin time (aPTT)
- Anti-Xa assay
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Heprain-induced thrombocytopenia (HIT) is due to what underlying mechanism?
Immunogenicitiy of the complex of heparin with platelet factor 4 (PF4)
What 2 things should you be looking for in a patient on Heparin?
- Thrombocytopenia
- Thrombosis
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Treatment for hepain-induced thrombocytopenia?
Discontinue heparin and administer DTI
What are 4 contraindications for using Heparin?
- Severe HTN
- Active TB
- Ulcers of GI tract
- Patients w/ recent surgeries
What is used clinically for reversal (antidote) of heparin action?
Protamine sulfate
The synthetic pentasaccharide, Fondaparinux, used as an anticoagulant binds to and inhibits what?
Acts as antithrombin III catalyst –> indirectly inhibit factor Xa (NO effect on thrombin)
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In what 3 ways does the anticoagulant, Fondaparinux, differ from heparins?
- Does not inhibit thrombin acitivity
- Rarely induces HIT (thrombocytopenia)
- Action is not reversed by Protamine sulfate
What are 3 clinical indications for the use of Fondaparinux?
- Prevention of DVT’s
- Tx of acute DVT (in conjunction w/ Warfarin)
- Tx of pulmonary embolism
Which parenteral direct thrombin inhibitor binds only at the thrombin active site?
Argatroban
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Which parenteral direct thrombin inhibitor is an irreversible inhibitor of thrombin?
Lepirudin
Which parenteral direct thrombin inhibitor is a reversible inhibitor of thombin and also inhibits platelet aggregation?
Bivalirudin
*Think Bi = 2 mechanisms!
Which parenteral direct thrombin inhibitor is short acting and used IV?
Argatroban
What are the clinical indications for the parenteral direct thrombin inhibitors?
What are bivalirudin and argatroban used for specifically?
- HIT
- Coronary angioplasty (bivalirudin and argatroban)
Repeated lepirduin use may cause what?
Anaphylactic rxn
Bleeding is an adverse effect of parenteral direct thrombin inhibitors and why may this potentially be a big deal?
No antidote exists
What is the MOA of Warfarin?
- Inhibits reactivation of vitamin K, by inhibiting vit K epoxide reductase
- Inhibits carboxylation of glutamate residues by GGCX in prothrombin and factors VII, IX, and X
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List 4 causes of high variability in therapeutic warfarin concentrations between individuals?
- Genetic make-up
- Disease states
- Drug-Drug interactions
- Diet
Warfarin has a narrow therapeutic window therefore the dose is titrated based on what lab testing?
At what range should patients be at?
- Prothrombin time (PT/INR)
- 2.0-3.0 range for pt’s on Warfarin
- INR is monitored a patients visit the clinic regularly
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Which stereoisomer of Warfari in 3-5x more potent?
S-isomer
Which steroisomer of Warfarin is metabolized primarily by CYP2C9?
S-isomer
What is the bioavailability of Warfarin when administered orally?
Onset and half-life?
- 100% bioavailability
- Delayed onset of action (12 hours)
- Long half-life (36 hrs)
99% of Warfarin is bound to what in the plasma?
Plasma albumin
What are 3 clincial uses for Warfarin?
- Prevent thrombosis or prevent/treat thromboembolism
- Atrial fibrillation
- Prosthetic heart valves
What are the major AE’s associated with Warfarin?
- Teratogenic effect (bleeding disorder in fetus, abnormal bone formation)
- Skin necrosis, infarction of breasts, intestines, extremities
- Osteoporosis
- Bleeding
Individual variability in the action of Warfarin may be to genetic factors including a high dose and low dose haplotype of what?
VKORC1
The high dose haplotype of VKORC1 for warfarin is more common in which ethnic group?
African Americans = more resistant to warfarin
The low dose haplotype of VKORC1 for warfarin is more common in which ethnic group?
Asian Americans = less resistant to warfarin
Which CYP is responsible for the individual variations in warfarin dose seen in some Caucasian pt’s?
CYP2C9
What are 3 pharmacokinetic interactions of Warfarin?
- CYP enzyme induction
- CYP enzyme inhibition
- Reduced plasma protein binding
What are 3 pharmacodynamic interactions associated with Warfarin?
- Synergism with other antithrombotic drugs
- Competitive antagonism (Vit K)
- Clotting factor concentration (diurectics)
Which 2 disease states must be accounted for when treating with Warfarin due to possibility of increased prothrombin time?
- Liver diseases (reduced clotting factor synthesis)
- Thyroid status –> Hyperthyroidism
What are 3 pharmacodynamic drug interactions of warfarin associated with increased prothrombin time?
- Aspirin (high doses)
- Cephalosporins, 3rd Gen.
- Heparin
What are 3 pharmacokinetic drug interactions of warfarin associated with decreased prothrombin time?
- Barbituates
- Cholestyramine
- Rifampin
What are 2 pharmacodynamic drug interactions of warfarin associated with decreased prothrombin time?
- Diuretics
- Vitamin K
List 4 advantages of using Warfarin.
- Oral administration
- Long duration of action
- Drug clearance is independent of renal function
- Reversal of action strategy has been developed
How can reversal of Warfarin action be accomplished?
What if rapid reversal needed?
- Vit K administration will reverse action in 12-24 hours
- More rapid reversal give fresh frozen plasma or prothrombin complex concentrate
What are 3 drawbacks of using Warfarin?
- Very high dosing variability, hard to maintain optimal concentration
- May lead to bleeding complications, such as intracranial hemorrhages
- Requires INR monitoring
Direct ORAL anticoagulants consist of three factor Xa inhibitors and a direct thrombin inhibitor, what are the drugs in these classes?
- Factor Xa inhibitors: Rivaroxaban, Apixaban, and Edoxaban
- Direct thrombin inhibitor: Dabigatran
What are the 3 clinical uses of the direct oral anticoagulants, which are Factor Xa inhibitors (Rivaroxaban, Apixaban, Edoxaban)?
- Prevention of thromboembolism
- Treatment of thromboembolism
- Prevention of stroke in patients w/ atrial fibrillation
What are 4 clinical advantages of using direct oral anticoagulants, which are Factor Xa inhibitors (Rivaroxaban, Apixaban, Edoxaban)?
- Given orally
- Administered at fixed doses and do NOT require monitoring
- Show non-inferiority compared with Warfarin
- Rapid onset of action as compared to warfarin
What is one drawback of direct oral anticoagulants, which are Factor Xa inhibitors (Rivaroxaban, Apixaban, Edoxaban)?
Excreted by kidneys; dose adjustment is needed in renal pts
What are the 2 clinical uses of the oral direct thrombin inhibitor, Dabigatran?
- Reduce the risk of stroke and systemic embolism in patients w/ non-valvular atrial fibrillation
- Tx of venous thromboembolism
What is the approved antidote for the oral direct thrombin inhibitor, Dabigatran?
Idarucizumab
What is a disadvantage associated w/ the oral direct thrombin inhibitor, Dabigatran?
80% renal excretion - may not be suitable in renal pt’s
What are some of the advantages of the oral direct thrombin inhibitor, Dabigatran?
- Predictable pharmacokinetics and bioavailability
- Fixed dosing and predictable anticoagulant action (no INR monitoring required)
- Rapid onset and offset of actions
- No interaction w/ P-450 metabolized drugs
What is the antidote for the DOAC - FXa inhibitors (rivaroxaban, apixaban, and edoxaban)?
Andexanet alfa
Which blood coagulation test is used for the direct oral anticoagulants, which are FXa inhibitors (rivaroxaban, apixaban, edoxaban)?
Anti-Xa
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Which blood coagulation test is used for the oral direct thrombin inhibitor, Dabigatran?
Diluted thrombin time (TT)
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Which antiplatelet drug is an inhibitor of thromboxane A2 synthesis?
Aspirin
What are the 4 ADP receptors blockers used as antiplatelet drugs?
- Clopidogrel
- Prasugrel
- Ticlopidine
- Ticagrelor
What are the 3 platelet glycoprotein receptor (GP IIb/IIIa) antagonists used as antiplatelet drugs?
- Abciximab
- Eptifibatide
- Tirofiban
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What are the 2 inhibitors of phosphodiesterases used as antiplatelet drugs?
- Dipyridamole
- Cilostazol
What are the clinical uses of Aspirin as an antiplatelet?
- Primary and seconday prevention of a heart attack
- And other vascular events –> ischemic stroke, arterial thrombosis of the limbs resulting in intermittent claudication
What are 2 AE’s associated with Aspirin?
- Peptic Ulcer
- GI bleeding
What is the MOA of the antiplatelets which are blockers of ADP receptors?
- Inhibition of AC by αi is relieved
- Increased production of cAMP
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What is the MOA of the antiplatelet drugs which are inhibitors of phosphodiesterase?
- Inhibition of cAMP degradation
- Levels of cAMP in platelets are increased
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The high variability of action of the antiplatelet drug, Clopidogrel is related to metabolism by what?
CYP2C19
Nonfunctional CYP2C19 allele is present in which ethnicities and has an effect on the action of the antiplatelet drug, Clopidogrel?
- Chinese (50%)
- African Americans (25%)
- Caucasians and Mexican-Americans (19%)
Cilostazol (inhibitor of phosphodiesterase) is primarily used for what?
Treat intermittent claudication
Dipyridamole (PDE inhibitor) is used with aspirin to prevent what?
Cerebrovascular ischemia
Dipyridamole (PDE inhibitor) is used with warfarin in which patients?
Those w/ prosthetic heart valves
What is the MOA of the fibrinolytic (thrombolytic) drugs?
Activate endogenous fibrinolytic system by converting plasminogen —> plasmin
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What are the 3 tissue-type plasminogen activator drugs which are fibrinolytic?
- Alteplase
- Reteplase
- Tenecteplase
What is the Urokinase-type plasminogen activator drug used as a fibrinolytic?
Urokinase
Which 3 classes of drugs are used as thrombolytic (fibrinolytic) drugs?
- Tissue-type plasminogen activator
- Urokinase-type plasmingoen activator
- Streptokinase preparations
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What are 5 clinical uses for the thrombolytic (fibrinolytic) drugs?
- Acute embolic/thrombotic stroke (within 3 hrs)
- Acute MI (withing 3-6 hrs)
- Pulmonary embolism
- DVT
- Ascending thrombophlebitis
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What is an AE associated with the fibrinolytic drugs, streptokinase and urokinase?
Bleeding from the systemic fibrinogenolysis
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Allergic reactions are an AE associated with what fibrinolytic drug?
Streptokinase
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Which fibrinolytic drugs need fibrin as coactivator?
tPA