Which antiplatelet medications are recommended for use, including aspirin, clopidogrel, prasugrel, ticagrelor, dipyridamole, cilostazol, and intravenous glycoprotein IIb/IIIa inhibitors?

Antiplatelet Medications

The primary antiplatelet medications include aspirin, P2Y12 inhibitors (clopidogrel, prasugrel, ticagrelor), intravenous glycoprotein IIb/IIIa inhibitors (abciximab, eptifibatide, tirofiban), and less commonly used agents like dipyridamole and cilostazol.

Core Antiplatelet Agents

Aspirin

• Dosing: Initial loading dose of 150-325 mg (or 75-250 mg IV), followed by maintenance dose of 75-100 mg daily 1, 2
• Mechanism: Irreversibly inhibits COX-1, reducing thromboxane A2 formation
• Role: First-line antiplatelet for all acute coronary syndromes and stroke prevention unless contraindicated 3, 1, 4
• Important caveat: When used with ticagrelor, aspirin maintenance dose must not exceed 81-100 mg daily to avoid reducing ticagrelor's efficacy 1, 4, 2

P2Y12 Inhibitors (ADP Receptor Antagonists)

Clopidogrel

• Dosing: 300-600 mg loading dose, then 75 mg daily 1, 2
• Use when: Prasugrel or ticagrelor are unavailable, contraindicated, or not tolerated 1, 2
• Advantages: Lower bleeding risk than newer P2Y12 inhibitors; extensive real-world experience
• Limitations: Variable response due to genetic polymorphisms (CYP2C19); slower onset and less potent than prasugrel/ticagrelor 5

Prasugrel

• Dosing: 60 mg loading dose, then 10 mg daily (reduce to 5 mg daily if weight <60 kg or age ≥75 years) 3, 1, 6
• Contraindications: Absolute contraindication in patients with prior stroke or TIA 3, 4, 6
• Advantages: More consistent and potent platelet inhibition than clopidogrel; no genetic variability affecting metabolism 5, 6
• When to use: Preferred in P2Y12-naïve ACS patients proceeding to PCI, particularly those with diabetes or prior MI 2, 6
• Critical warning: Do not start if urgent CABG likely; discontinue at least 7 days before surgery 6

Ticagrelor

• Dosing: 180 mg loading dose, then 90 mg twice daily 3, 1, 4
• Advantages: Reversible binding (faster offset than clopidogrel/prasugrel); can be used regardless of prior clopidogrel therapy 3, 7
• When to use: Preferred over clopidogrel in NSTE-ACS patients with early invasive or ischemia-guided strategy 1
• Important: Discontinue at least 5 days before surgery 7

Glycoprotein IIb/IIIa Inhibitors (IV only)

Abciximab

• Dosing: 0.25 mg/kg IV bolus, then 0.125 mcg/kg/min infusion (max 10 mcg/min) 4
• Use: Bail-out during PCI for no-reflow or thrombotic complications 1, 2
• Contraindication: Should NOT be given to patients in whom PCI is not planned 3, 8

Eptifibatide

• Dosing: 180 mcg/kg IV bolus (repeat in 10 min), then 2 mcg/kg/min infusion 4
• Renal adjustment: Reduce infusion by 50% if CrCl <50 mL/min; avoid in hemodialysis 4

Tirofiban

• Dosing: 25 mcg/kg IV bolus, then 0.15 mcg/kg/min infusion 4
• Renal adjustment: Reduce infusion by 50% if CrCl <30 mL/min 4

Less Common Agents

Dipyridamole

• Dosing: 25/200 mg (with aspirin) twice daily 9
• Primary use: Stroke prevention in combination with aspirin 9, 10
• Mechanism: Inhibits adenosine uptake and phosphodiesterase-5 11

Cilostazol

• Dosing: Typically 100 mg twice daily
• Primary use: Peripheral artery disease; occasionally used in stroke prevention 9, 12
• Mechanism: Phosphodiesterase III inhibitor 13

Clinical Decision Algorithm

For Acute Coronary Syndromes (NSTE-ACS/STEMI):

1. Immediate: Aspirin 162-325 mg loading dose 1, 4
2. Add P2Y12 inhibitor:
   • First choice: Prasugrel 60 mg OR ticagrelor 180 mg (if no prior stroke/TIA) 1, 2
   • Use clopidogrel 600 mg only if prasugrel/ticagrelor unavailable or contraindicated 1, 2
3. Duration: Continue dual antiplatelet therapy for 12 months 3, 1, 14
4. GP IIb/IIIa inhibitors: Reserve for bail-out situations during PCI 1, 2

For Stroke/TIA:

1. Minor stroke (NIHSS ≤3) or high-risk TIA: Aspirin 160-325 mg + clopidogrel 300-600 mg loading, then aspirin 81 mg + clopidogrel 75 mg daily for 21 days, followed by single antiplatelet 9
2. Non-cardioembolic stroke: Long-term single antiplatelet (aspirin 81-325 mg, clopidogrel 75 mg, or aspirin/dipyridamole) 9, 10

Critical Bleeding Risk Considerations:

• Prasugrel: Higher bleeding risk than clopidogrel; avoid if weight <60 kg (use 5 mg dose), age ≥75 years (unless high-risk diabetes/prior MI), or prior stroke 6
• All agents: Increased bleeding with concomitant anticoagulants, NSAIDs, or in patients with renal impairment 6