Aspirin - NextBio

Treatment

Aspirin

Description:	The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. (From Martindale, The Extra Pharmacopoeia, 30th ed, p5)
Drug Type:	Small Molecule; Approved
Pharmacology:	Aspirin (acetylsalicylic acid) is an analgesic, antipyretic, antirheumatic, and anti-inflammatory agent. Aspirin's mode of action as an antiinflammatory and antirheumatic agent may be due to inhibition of synthesis and release of prostaglandins. Aspirin appears to produce analgesia by virtue of both a peripheral and CNS effect. Peripherally, Aspirin acts by inhibiting the synthesis and release of prostaglandins. Acting centrally, it would appear to produce analgesia at a hypothalamic site in the brain, although the mode of action is not known. Aspirin also acts on the hypothalamus to produce antipyresis; heat dissipation is increased as a result of vasodilation and increased peripheral blood flow. Aspirin's antipyretic activity may also be related to inhibition of synthesis and release of prostaglandins.
Mechanism of Action:	The analgesic, antipyretic, and anti-inflammatory effects of aspirin are due to actions by both the acetyl and the salicylate portions of the intact molecule as well as by the active salicylate metabolite. Aspirin directly and irreversibly inhibits the activity of both types of cyclo-oxygenase (COX-1 and COX-2) to decrease the formation of precursors of prostaglandins and thromboxanes from arachidonic acid. This makes aspirin different from other NSAIDS (such as diclofenac and ibuprofen) which are reversible inhibitors. Salicylate may competitively inhibit prostaglandin formation. Aspirin's antirheumatic (nonsteroidal anti-inflammatory) actions are a result of its analgesic and anti-inflammatory mechanisms; the therapeutic effects are not due to pituitary-adrenal stimulation. The platelet aggregation–inhibiting effect of aspirin specifically involves the compound's ability to act as an acetyl donor to the platelet membrane; the nonacetylated salicylates have no clinically significant effect on platelet aggregation. Aspirin affects platelet function by inhibiting the enzyme prostaglandin cyclooxygenase in platelets, thereby preventing the formation of the aggregating agent thromboxane A2. This action is irreversible; the effects persist for the life of the platelets exposed. Aspirin may also inhibit formation of the platelet aggregation inhibitor prostacyclin (prostaglandin I2) in blood vessels; however, this action is reversible.
Indication:	For use in the temporary relief of various forms of pain, inflammation associated with various conditions (including rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis, and ankylosing spondylitis), and is also used to reduce the risk of death and/or nonfatal myocardial infarction in patients with a previous infarction or unstable angina pectoris.
Half Life:	The plasma half-life is approximately 15 minutes; that for salicylate lengthens as the dose increases: doses of 300 to 650 mg have a half-life of 3.1 to 3.2 hours; with doses of 1 gram, the half-life is increased to 5 hours and with 2 grams it is increased to about 9 hours.

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