(synonymous with acetylsalicylic acid, ASA)


There are multiple brands.


  • Tablets: 81 mg, 325 mg, 500 mg
  • Capsules: 325 mg


Primarily used as an analgesic, aspirin can also be classed with NSAIDs. It has the ability to suppress the production of prostaglandins and thromboxanes by irreversibly inactivating cyclooxygenase. This action, however, makes it slightly different from some of the other NSAIDs that are “reversible” inactivators of cyclooxygenase (e.g., ibuprofen).

By inactivating cyclooxygenase and suppressing prostaglandins and thrombaxnes, aspirin is able to block generating pain impulses peripherally, and inhibit inflammation. It reduces fever by acting on the heat regulating center to produce peripheral vasodilation. It is also able to effect platelet aggregation which helps to prevent clots.

Aspirin is rapidly absorbed and well distributed in the body by way of the stomach and small intestine. It crosses the placental barrier. It is metabolized in the liver and excreted by the kidneys through filtration and renal tubular secretion.


Used for mild to moderate pain, inflammation, and fever.

Drug Interactions or Contraindications

  • Contraindicated in bleeding disorders. Should be used cautiously where hepatic failure or impaired renal function are present.
  • Due to its effect on platelets, aspirin should be stopped one week prior to any surgical procedures.
  • Use with other NSAIDs will increase risk of GI bleeding; avoid using together.
  • Corticosteroids decrease salicylate effect.
  • Furosemide may increase salicylate toxicity by delaying its excretion.
  • Concomittant use with aminoglycosides may increase chance of nephrotoxicity.

Adverse Reactions

EENT:  hearing loss

Blood:  prolonged bleeding time

GI:  GI distress, anorexia (loss of appetite), occult bleeding

Skin:  bruising

Other:  hypersensitivity with asthma like conditions

Dosage Recommendations

100 mg/kg, PO, q4hr   2


100 mg/kg, PO, q48hr  27,  26,  34


50 mg/kg to 150 mg/kg, PO, q4hr to q8hr   41,  42,  44


100 mg/kg to 150 mg/kg, PO, q4hr   1,  26,  27,  34


  • Give with food to prevent GI irritation.
  • Watch for black stools, which may indicate bleeding.
  • Do not give one week prior to any surgery.
  • If mixing with liquid use immediately since it does not stay stable in solution.
  • Store in tightly closed container away from moisture.
  • Aspirin that becomes discolored or has vinegar like smell should be discarded.


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