64 Questions
What is the primary effect of antiplatelet medications on blood coagulation?
Inhibition of platelet activation
What are the two main ADP receptors on the platelet membrane involved in platelet aggregation?
P2Y12 and P2Y1
What is the most significant adverse effect associated with antiplatelet and anticoagulant medications?
Bleeding
What is the main therapeutic use of antiplatelet medications?
Secondary prevention of coronary artery disease and stroke
What is the primary mechanism of platelet activation in response to vascular injury?
Binding of proteins to platelet receptors
What is the precaution that should be taken when considering antiplatelet or anticoagulant therapy in patients with certain medical conditions?
Assess risk of bleeding due to coagulopathies or other diseases
What is the outcome of TXA2 activation on the platelet membrane?
Activation of GPIIb/IIIa receptors
Which antiplatelet medication inhibits the enzyme responsible for breakdown of cAMP in platelet?
Dipyridamole
What is the outcome of thrombin activation on platelets?
Stimulation of ADP and TXA2 release
What is the mechanism of action of aspirin as an antiplatelet medication?
Irreversible inhibition of COX-1 enzyme
What is the indication for aspirin use in acute coronary syndrome?
Chew 162-325 mg immediately in emergency department
Which of the following is a PAR-1 receptor inhibitor?
Vorapaxar
What is the indication of clopidogrel in acute coronary syndrome?
As part of dual antiplatelet regimen with aspirin
What is the mechanism of clopidogrel's therapeutic effect?
Irreversible inhibition of P2Y12 receptor
What is the potential effect of smoking on clopidogrel's therapeutic effect?
Increased conversion to active metabolite
What is the potential interaction between clopidogrel and proton pump inhibitors (PPIs)?
PPIs decrease the conversion of clopidogrel to its active metabolite
What is the reason for the variable response to clopidogrel in some patients?
Genetic polymorphisms in CYP2C19
What is the boxed warning related to clopidogrel?
Higher prevalence of genetic polymorphisms in CYP2C19 in Eastern Asians
What is the indication of prasugrel in patients with acute coronary syndrome?
to reduce the risk of thrombotic cardiovascular events in patients who are to be managed with PCI
Which of the following is a boxed warning for prasugrel?
Increased risk of bleeding
What is the difference between ticagrelor and clopidogrel in terms of conversion to active metabolite?
Different CYP enzymes are responsible for conversion to active metabolite
Which of the following is a contraindication for prasugrel?
All of the above
What is the mechanism of action of ticagrelor?
P2Y12 (ADP) receptor inhibitor, reversible
Which of the following is a notable, rare adverse effect of prasugrel and ticagrelor?
TTP
What is the recommended loading dose of aspirin for acute coronary syndrome?
162-325 mg
Which P2Y12 inhibitor is preferred for acute coronary syndrome patients who require PCI?
Ticagrelor or Prasugrel
What is the primary benefit of dual antiplatelet therapy (DAPT) in patients with acute coronary syndrome?
Preventing stent thrombosis and lowering the risk of adverse events due to plaque rupture
In which patients is antiplatelet therapy contraindicated?
Those with a history of stroke, TIA, or intracranial hemorrhage
What is the typical duration of dual antiplatelet therapy (DAPT) in patients with acute coronary syndrome?
12 months
Which trial supported the preference for ticagrelor over clopidogrel in non-invasive treatment of acute coronary syndrome?
PLATO
What is the result of TXA2 activation on the platelet membrane?
Activation of GPIIb/IIIa receptors
Which of the following antiplatelet medications acts by inhibiting the breakdown of cAMP in platelets?
Dipyridamole
What is the common pathway of platelet activation in response to vascular injury?
TXA2 and ADP signaling
What is the primary effect of antiplatelet medications on blood coagulation?
Inhibition of platelet aggregation
Which of the following antiplatelet medications is an ATP analogue?
Cangrelor
What is the duration of the antiplatelet effect of aspirin?
Until new platelets are generated
What is the recommended dose range for aspirin as an antiplatelet medication?
81 mg - 325 mg
Which of the following is a contraindication for aspirin use in patients undergoing total hip or total knee arthroplasty?
Patients at higher risk for clot
What is the effect of omeprazole on clopidogrel's therapeutic effect?
Decreases the therapeutic effect
What is the benefit of spacing out daily aspirin from other non-selective NSAIDs in patients undergoing total hip or total knee arthroplasty?
Prevents the inhibition of aspirin's antiplatelet effect
Which of the following medications is used for secondary prevention of ischemic stroke or TIA?
Clopidogrel
What is the effect of smoking on CYP enzymes involved in clopidogrel's conversion to its active metabolite?
Induces the CYP enzymes
What is the primary effect of antiplatelet medications on platelet activation?
Inhibiting platelet adherence to injured vascular endothelium
What is the role of Von Willebrand factor in platelet activation?
Releasing proteins that bind to platelet receptors
Which of the following medications is NOT an antiplatelet drug?
Warfarin
What is the result of platelet activation in response to vascular injury?
Formation of a thrombus
Which of the following is NOT a mechanism of platelet activation?
Fibrinogen release
What is the primary therapeutic use of antiplatelet medications?
Secondary prevention of coronary artery disease and stroke
What is the mechanism of action of ticagrelor in platelet inhibition?
Reversibly binding to an area distinct from the ADP binding site
Which of the following P2Y12 receptor inhibitors has a boxed warning for bleeding risk?
All of the above
What is the primary indication for dipyridamole?
Ischemic stroke or TIA
What is the mechanism of action of cilostazol in platelet inhibition?
Inhibiting the phosphodiesterase III enzyme
Which of the following antiplatelet medications is contraindicated in heart failure of any severity?
Cilostazol
What is the main therapeutic benefit of vorapaxar?
Reduction in cardiovascular events in patients with prior MI or PAD
What is the primary route of excretion for eptifibatide?
Renal
Which of the following antiplatelet medications has a long receptor dissociation time?
Vorapaxar
What is the primary side effect of dipyridamole?
Headache
Which of the following antiplatelet medications is not routinely used?
Vorapaxar
What is the primary benefit of dual antiplatelet therapy (DAPT) in patients with acute coronary syndrome?
Preventing stent thrombosis and lowering the risk of adverse events due to plaque rupture
In which patients should antiplatelet medications be avoided?
Those with a history of stroke, TIA, or intracranial hemorrhage
What is the typical duration of dual antiplatelet therapy (DAPT) in patients with acute coronary syndrome?
12 months
What is the primary complication of dual antiplatelet therapy (DAPT)?
Bleeding
What is the loading dose of aspirin recommended for acute coronary syndrome?
162-325 mg
Which P2Y12 inhibitor is preferred for acute coronary syndrome patients who require PCI?
Ticagrelor or prasugrel
Study Notes
Antiplatelet Drugs
- Antiplatelet drugs are divided into five classes: cyclooxygenase inhibitors, phosphodiesterase inhibitors, GPIIb/IIIa inhibitors, P2Y12 receptor inhibitors, and PAR-1 receptor inhibitors
- Antiplatelet drugs are used to prevent platelet aggregation and reduce the risk of cardiovascular events
Cyclooxygenase Inhibitors
- Aspirin is an example of a cyclooxygenase inhibitor
- Aspirin works by irreversibly inhibiting COX-1, which inhibits the synthesis of TXA2
- Aspirin's antiplatelet effect lasts for 24-36 hours, until new platelets are generated
- Aspirin has adverse effects such as GI upset, tinnitus, hypersensitivity reaction, and bleeding (GI mostly, but also rarely ICH)
P2Y12 Receptor Inhibitors
- Examples of P2Y12 receptor inhibitors include clopidogrel, ticagrelor, and prasugrel
- These drugs work by blocking the P2Y12 receptor on the platelet surface, which prevents activation of the GPIIb/IIIa receptor complex and reduces platelet aggregation
- Indications for P2Y12 receptor inhibitors include acute coronary syndrome, secondary prevention of atherosclerotic cardiovascular disease, and peripheral arterial disease
Phosphodiesterase Inhibitors
- Examples of phosphodiesterase inhibitors include dipyridamole and cilostazol
- These drugs work by inhibiting the enzyme responsible for breaking down cAMP in platelets, which increases cAMP and reduces platelet aggregation
GPIIb/IIIa Inhibitors
- Examples of GPIIb/IIIa inhibitors include eptifibatide and tirofiban
- These drugs work by blocking the GPIIb/IIIa receptors on the platelet surface, which prevents fibrinogen binding and reduces platelet aggregation
PAR-1 Receptor Inhibitors
- Vorapaxar is an example of a PAR-1 receptor inhibitor
- This drug works by blocking the PAR-1 receptor on platelets, which inhibits thrombin-induced and thrombin receptor agonist peptide (TRAP)-induced platelet aggregation### Ticagrelor
- Reversibly binds to an area distinct from the ADP binding site, allowing redistribution to new platelets as they are formed
- PLATO trial: reduced composite primary end point (death from vascular causes, MI, or stroke) compared to clopidogrel, with no difference in bleeding risk
- Boxed warning for bleeding risk, contraindicated in active bleeding or urgent CABG
- Concomitant aspirin dose must be ≤100mg
Ticagrelor Pharmacokinetics
- Onset of effect: 30 minutes
- Time to maximum effect: 2-3 hours
- Platelet function returns to baseline: 5 days
Thrombotic Thrombocytopenic Purpura (TTP)
- Thrombotic microangiopathy caused by small vessel platelet thrombi
- Leads to thrombocytopenia and hemolytic anemia
- Common drug causes: chemotherapeutic agents, immunosuppressive agents, drugs of abuse, and emicizumab
- Possible link to P2Y12 receptor antagonists (clopidogrel and ticlopidine)
GPIIb/IIIa Receptor Inhibitors
- Eptifibatide and tirofiban (abciximab)
- MOA: prevents cross-linking by interfering with fibrinogen binding to GPIIb/IIIa receptor
- Indications: acute coronary syndrome, primary PCI, alternative
- Renal dose adjustment required
- Adverse effects: bleeding
- Contraindications: active bleeding, history of stroke, severe HTN, major surgery, HD
Dipyridamole
- MOA: phosphodiesterase inhibitor, increases cAMP, inhibits platelet function and causes vasodilation
- Formulated as a capsule in combination with aspirin (Aggrenox)
- Indication: secondary prevention of ischemic stroke or TIA
- Off-label uses: hemodialysis graft patency, symptomatic carotid artery stenosis
- Adverse effects: headache, hypotension, GI side effects, tinnitus
Cilostazol
- MOA: phosphodiesterase III inhibitor, increases cAMP, inhibits platelet aggregation and causes vasodilation
- Indication: intermittent claudication in peripheral artery disease
- Boxed warning: contraindicated in heart failure of any severity
- Adverse effects: headache, diarrhea, dizziness, palpitations
- High fat meals increase absorption, take between meals
- Drug interactions with CYP inhibitors increase cilostazol level
Vorapaxar
- PAR-1 receptor antagonist
- Indication: History of MI or established Peripheral Arterial Disease
- PK: long t1/2 = about 8 days, long receptor dissociation time
- Inhibition of platelet aggregation lasts up to 4 weeks after discontinuation
- Boxed warning: Bleeding risk
Test your knowledge of antiplatelet drugs, including their mechanism of action, antiplatelet actions, administration and elimination, adverse effects, and drug interactions. This quiz covers the key concepts and details of each drug class.
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