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Aspirin (acetylsalicylic acid, ASA)

Non-steroidal anti-inflammatory drug (NSAID) / antiplatelet

Mechanism of action

Irreversibly acetylates cyclooxygenase-1 (COX-1) in platelets, blocking thromboxane A2 production for the platelet's lifespan (~10 days). At low doses (81 mg), the antiplatelet effect dominates; at higher doses, anti-inflammatory and analgesic effects appear. Used for primary and secondary cardiovascular prevention, acute MI/stroke (chew 162–325 mg), and pain/inflammation.

Adverse effects

Life-threatening / NCLEX-tested

  • GI bleeding and ulceration (dose-dependent)
  • Hemorrhagic stroke
  • Reye's syndrome — life-threatening encephalopathy in children with viral illness; absolute contraindication under age 18
  • Salicylate toxicity (tinnitus, hyperventilation, metabolic acidosis at high doses)
  • Bronchospasm and anaphylaxis in NSAID-sensitive asthma
  • Acute kidney injury, especially with dehydration

Side effects

Common — what to teach

  • Dyspepsia, heartburn
  • Mild GI upset
  • Easy bruising
  • Tinnitus (early sign of toxicity)
  • Allergic rash

Food & drug interactions

Bleeding risk multiplies with warfarin, heparin, DOACs, clopidogrel, and SSRIs. NSAIDs (ibuprofen) can blunt aspirin's antiplatelet effect — separate doses (take aspirin first, ibuprofen 30+ minutes later or 8+ hours before). Alcohol raises GI bleed risk. Reduces uric acid excretion at low dose — gout risk.

Nursing implications

Assessment, monitoring, patient teaching

  • Teach to chew (not swallow whole) 162–325 mg ASAP for suspected MI
  • For chronic prophylaxis, take with food or after meals to limit GI irritation
  • Stop 7–10 days before elective surgery (irreversible platelet effect — must wait for new platelets)
  • Do not give to children with viral illness — Reye's syndrome
  • Counsel about black/tarry stools, vomiting blood, easy bruising, and tinnitus
  • Use enteric-coated for chronic dosing if GI upset is an issue (GI bleed risk persists, but symptoms may decrease)

When to hold / contraindications

  • Active GI bleed or significant bleeding from any site
  • Children/teens with viral illness
  • Severe asthma with documented NSAID hypersensitivity
  • Pre-surgical hold per protocol (typically 7–10 days)
  • Pregnancy after 20 weeks (avoid except low-dose for specific obstetric indications under specialist care)

Memory anchor

"Aspirin at 81 mg saves hearts; aspirin in viral kids causes Reye's." Chew it for an MI. Stop 7–10 days before surgery — platelets need to regenerate.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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