Platelet Inhibitors Flashcards

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Questions and Answers

Name the anti-platelet drugs:

Ibuprofen, Dipyridamole

Aspirin, Clopidogrel

Aggrenox, Prasugrel

Aspirin, Aggrenox (ER Dipyridamole + ASA), Clopidogrel (Plavix), & Prasugrel (correct)

What is the technical name for Aspirin?

acetylsalicylic acid (ASA)

What is the mechanism of Aspirin?

Aspirin is an NSAID. It irreversibly inhibits the enzyme cyclooxygenase, preventing conversion of arachidonic acid to thromboxane A2.

Why is low dose Aspirin a better antiplatelet than high-dose Aspirin?

Higher doses inhibit cyclooxygenase and prostacyclin, while low-dose aspirin does not inhibit PGI2. Signup and view all the answers

How long do the antiplatelet effects of Aspirin last?

the life of the platelet (5-7 days) Signup and view all the answers

What is the onset of the antiplatelet action of ASA?

very fast (within 60 minutes) Signup and view all the answers

What dose is considered low dose or cardiac dose ASA?

81 mg (baby aspirin) - 325 mg PO daily Signup and view all the answers

What are adverse effects of ASA?

Allergic reactions, upset stomach, GI ulcers, and excessive bleeding. Signup and view all the answers

ASA withdrawal has been associated with _____________.

an increased risk of clots Signup and view all the answers

What are the drug interactions of ASA?

Ibuprofen may block antiplatelet benefits and increases risk of GI ulceration/bleeding. Signup and view all the answers

What is the mechanism of action of Dipyridamole?

Dipyridamole inhibits phosphodiesterase, leading to accumulation of cAMP & cGMP. Signup and view all the answers

What is Dipyridamole used in conjunction with?

ASA Signup and view all the answers

What are the adverse effects of Aggrenox?

Headache, GI upset, N/V, diarrhea, dizziness. Signup and view all the answers

What are the drug interactions of Aggrenox?

Same as with ASA: Ibuprofen may block benefits, and increases risk of ulceration/bleeding. Signup and view all the answers

What is the mechanism of action of Clopidogrel?

Inhibits platelet aggregation by inhibiting ADP receptors. Signup and view all the answers

What is the onset of Clopidogrel?

3-7 day lag time for onset of action Signup and view all the answers

What are the adverse effects of Clopidogrel?

GI disturbance, diarrhea, rash, dizziness, headache, and excessive bleeding. Signup and view all the answers

What is the bleeding risk of Clopidogrel?

bleeding risk greater than ASA but 75 years old. Signup and view all the answers

What are the adverse effects/drug interactions of Prasugrel?

Higher incidence of serious bleeding compared to Clopidogrel. Signup and view all the answers

Study Notes

Anti-Platelet Drugs

Common anti-platelet medications include Aspirin, Aggrenox (ER Dipyridamole + Acetylsalicylic Acid), Clopidogrel (Plavix), and Prasugrel.

Aspirin (Acetylsalicylic Acid)

Aspirin is an NSAID and acts by irreversibly inhibiting the enzyme cyclooxygenase, blocking the conversion of arachidonic acid to thromboxane A2, a potent vasoconstrictor and platelet aggregator.
Low-dose aspirin (81 mg to 325 mg) is preferred over high doses as it does not inhibit prostacyclin (PGI2), an endogenous antiplatelet factor.
Antiplatelet effects last for the lifespan of platelets, approximately 5-7 days, necessitating a 7-day cessation before surgery.
Rapid onset of action occurs within 60 minutes; chewing improves absorption, which is critical during acute myocardial infarction (MI).

Adverse Effects of Aspirin

Common adverse effects include allergic reactions, gastrointestinal discomfort, and risk for GI ulcers, particularly in older patients.
Low-dose cardiac aspirin is generally better tolerated compared to higher doses.
Withdrawal from aspirin therapy is associated with an increased risk of thrombotic events.
Drug interactions include reduced antiplatelet efficacy when combined with ibuprofen, and increased bleeding risks when used with other NSAIDs or anticoagulants.

Dipyridamole

Mechanism of action involves the inhibition of phosphodiesterase, which increases cAMP and cGMP, enhancing antithrombotic effects on vascular walls.
Often used in combination with aspirin as Aggrenox (200 mg ER Dipyridamole + 25 mg ASA), which is more expensive than aspirin alone.

Adverse Effects of Aggrenox

25% of patients experience side effects, with headache (10%), GI upset, nausea/vomiting, and dizziness being common.
May lead to excessive bleeding similar to other antiplatelet drugs.

Clopidogrel (Plavix)

Inhibits platelet aggregation by blocking ADP receptors; this prevents activation of nearby platelets.
Onset of action involves a delay of 3-7 days before reaching full efficacy.

Adverse Effects of Clopidogrel

Common side effects include GI disturbances, diarrhea, rash, dizziness, and headache. It shares a risk of excessive bleeding.
Although it is generally well-tolerated, if GI bleeding occurs, the mortality risk is significant.

Prasugrel

Associated with a higher incidence of serious bleeding compared to Clopidogrel.
Activation is not dependent on CYP2C19, thus reducing potential drug interactions with PPIs.

Overall Bleeding Risks

Clopidogrel presents a higher bleeding risk compared to aspirin, especially in older patients (≥75 years).
Monitoring and managing potential drug interactions is crucial to minimize risks associated with combined therapies.

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Description

This quiz covers essential anti-platelet drugs and their mechanisms. You will learn about drugs like Aspirin, Clopidogrel, and others, alongside their technical definitions. Perfect for students studying pharmacology and blood coagulation.