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Aspirin

anti-platelet drug

Mechanism

inhibiting cyclo-oxygenase.
shifts the balance in cells between thromboxane A₂(prothrombotic) and prostacyclin (inhibibitory)

Uses

Myocardial Infarction
TIA
Unstable Angina Pectoris
Vascular grafts
Peripheral Vascular Disease

Aspirin

Low dose aspirin, commonly 75mg, daily has been shown to be beneficial in the treatment of a number of vascular disorders, including myocardial ischaemia. It is an anti-platelet agent that helps to prevent thrombus formation and thrombus propagation following atheromatous plaque rupture.

Action

Aspirin acetylates and inactivates cyclooxygenase (COX), the enzyme required for production of the pro-aggregatory prostaglandin thromboxine A_2.This effect is permanent such that the effects of aspirin last for 10 days until sufficient new platelets have been synthesised.

Side effects

These include gastric erosions and GI bleeding, hypersensitivity reactions, and the precipitation of asthma. The use of aspirin is contraindicated in those with peptic ulceration or GI haemorrhage, bleeding disorders, renal or hepatic impairment, and those with known hypersensitivity.

Pharmacokinetics

Aspirin is rapidly absorbed from the upper GI tract. It undergoes presystemic hydrolysis to salicylate, such that platelet COX may be inhibited as platelets pass through the portal circulation without greatly affecting the synthesis of blood vessel prostacyclin, also catalysed by COX

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