Antiplatelets

Key Points

• Antiplatelet agents decrease platelet activation and aggregation; primary use is prevention and treatment of cardiovascular thromboembolic events.
• Aspirin inhibits COX-mediated thromboxane A2 production; P2Y12 inhibitors (clopidogrel, ticagrelor, prasugrel) block ADP receptor on platelets.
• Bleeding is the primary adverse effect across all antiplatelet classes; discontinue 5–7 days before surgery.
• Clopidogrel is a prodrug requiring CYP2C19 activation; genetic polymorphisms can cause therapeutic failure.
• Cangrelor provides near-immediate IV P2Y12 inhibition during PCI, with platelet-function recovery within about 1 hour after discontinuation.
• In older adults, dual antiplatelet therapy (for example clopidogrel plus aspirin) increases bleeding risk.
• In suspected acute MI pathways, aspirin is commonly given as a 325 mg chewable loading dose unless contraindicated.
• Clopidogrel 75 mg is a common maintenance P2Y12 dose in ACS/post-stent pathways when selected by the treating team.

Pathophysiology

Platelets adhere to injured vessel walls and aggregate to form the primary hemostatic plug. Platelet activation is mediated by ADP receptor (P2Y12), thromboxane A2, and GPIIb/IIIa receptors. Antiplatelet drugs block one or more of these pathways, reducing clot formation.

Common indications include: acute coronary syndrome (ACS), post-coronary stent placement, stroke prevention, peripheral arterial disease, and atrial fibrillation (with certain anticoagulants).

Classification

Subclass	Examples	Mechanism
COX inhibitor	Aspirin	Irreversibly inhibits COX → reduces thromboxane A2
P2Y12 inhibitors	Clopidogrel, ticagrelor, prasugrel, cangrelor	Block ADP receptor → prevent platelet aggregation
GPIIb/IIIa inhibitors	Abciximab, eptifibatide, tirofiban	Block fibrinogen receptor → most potent; IV use in ACS
PDE inhibitors	Dipyridamole, cilostazol	Increase cAMP → inhibit platelet aggregation

Nursing Assessment

NCLEX Focus

Monitor for bleeding; hold P2Y12 inhibitors 5–7 days before surgery; verify CYP2C19 status with clopidogrel use.

• Assess baseline CBC, PT/INR, aPTT, and platelet count before initiating therapy.
• Assess for concurrent anticoagulant, NSAID, or herbal supplement use (ginkgo, garlic, fish oil) — increased bleeding risk.
• Assess renal/hepatic function; prasugrel is contraindicated in prior stroke/TIA and has higher bleeding risk in patients <60 kg or age >75 years.
• Assess age/frailty and dual-therapy exposure; bleeding risk is higher in older adults taking clopidogrel plus aspirin.
• Assess for perioperative timing: most antiplatelets should be held 5–7 days pre-surgery per surgical team.
• Assess for bleeding progression using symptom cues (melena, hematuria, epistaxis, gingival bleeding, coffee-ground emesis, hemoptysis, or severe headache suggesting intracranial bleeding) plus hemoglobin/hematocrit trends.

Nursing Interventions

• Instruct patients to take aspirin with food to reduce GI adverse effects; enteric-coated formulations may decrease gastric irritation.
• For acute MI with aspirin indicated: have patient chew aspirin (not swallow whole) for rapid absorption, using protocol-directed loading dose (commonly 325 mg) when ordered.
• Teach patients not to take OTC NSAIDs concurrently with aspirin — pharmacodynamic drug interaction increases bleeding risk.
• Monitor for signs of bleeding: petechiae, bruising, blood in stool/urine, prolonged bleeding from minor cuts.
• In acute-MI use, watch for GI upset, expanding bruising, and blood in urine or stool as early toxicity cues.
• In chronic vascular-disease prevention pathways (for example carotid or aneurysmal atherosclerotic disease), reinforce long-term aspirin adherence when prescribed and monitor ongoing bleeding tolerance.
• During IV eptifibatide therapy, trend platelet count closely and notify provider promptly if platelets fall below 100,000/mm3.

Perioperative Antiplatelet Management

Discontinue clopidogrel, ticagrelor, prasugrel 5–7 days before elective surgery to reduce surgical bleeding risk. Never discontinue antiplatelet therapy in patients with recent coronary stent without provider guidance — stent thrombosis can be fatal.

Aspirin in Pediatrics

Aspirin is contraindicated in children younger than 12 years with flu-like or viral illness symptoms due to Reye syndrome risk (potentially fatal hepatic failure and encephalopathy).

Pharmacology

Drug	Route/Dose	Key Nursing Considerations
Aspirin	81–325 mg orally daily	Irreversible COX inhibition; GI risk; avoid in children with flu-like illness; chew for acute MI; overdose is functionally irreversible at the platelet level
Clopidogrel (Plavix)	75 mg orally daily	Prodrug via CYP2C19; genetic polymorphism risk; CYP2C19 inhibitors (e.g., omeprazole) reduce effectiveness; interaction risk with opioids, repaglinide, and grapefruit juice; avoid premature discontinuation after stent/ACS without provider guidance
Ticagrelor (Brilinta)	90 mg orally twice daily	Not a prodrug; dyspnea common side effect; do not exceed aspirin 100 mg/day with ticagrelor; contraindicated with prior intracranial hemorrhage
Prasugrel (Effient)	10 mg orally daily (5 mg daily if <60 kg)	Highest bleeding risk among oral P2Y12 options; contraindicated in prior stroke (stroke)/TIA; generally avoid age >75 years unless thrombotic risk is very high
Cangrelor (Kengreal)	30 mcg/kg IV bolus, then 4 mcg/kg/min infusion during PCI	IV-only P2Y12 inhibitor with immediate onset and rapid offset (platelet function recovery about 1 hour after stop)
Eptifibatide (Integrilin)	180 mcg/kg IV bolus, then 2 mcg/kg/min infusion (PCI may require second bolus at 10 min)	Potent GPIIb/IIIa inhibitor; major risk is profound thrombocytopenia and bleeding; monitor platelets closely

Clinical Judgment Application

Clinical Scenario

A patient taking clopidogrel for a coronary stent is scheduled for elective hip replacement surgery in 5 days.

• Recognize Cues: Antiplatelet use with upcoming surgery creating bleeding risk vs. stent thrombosis risk.
• Analyze Cues: 5 days is marginal; stent age determines whether antiplatelet therapy can be safely interrupted.
• Prioritize Hypotheses: Coordinated surgical/cardiological decision about antiplatelet continuation.
• Generate Solutions: Notify surgeon and cardiologist; do not discontinue without provider guidance.
• Take Action: Document stent type and date; facilitate provider communication; delay surgery if stent is <30 days old.
• Evaluate Outcomes: Surgical plan adjusted with appropriate antiplatelet management documented.

Related Concepts

• anticoagulants - Complementary hemostasis modulation; combination increases bleeding risk.
• coronary-artery-disease - Primary indication for antiplatelet therapy post-ACS or stent.
• deep-vein-thrombosis - Anticoagulants preferred over antiplatelets for VTE.
• nsaids - Pharmacodynamic interaction increasing GI and systemic bleeding risk.

Self-Check

1. Why should aspirin be chewed rather than swallowed in acute MI?
2. What CYP2C19 drug interaction limits clopidogrel effectiveness?
3. Why is prasugrel contraindicated in patients with prior stroke or TIA?