Aspirin
Aspirin (acetylsalicylic
acid) is a simple molecule first synthesized in Germany 150 years ago.
Its pain-relieving properties were recognized and exploited commercially
100 years ago. In the last 50 years, aspirin has been shown to have
remarkable antithrombotic benefits.
Aspirin's antithrombotic
effect is mediated by inhibition of blood platelets. The drug blocks
a platelet enzyme, cyclo-oxygenase, by acetylating the enzyme's active
site. Inhibition of the enzyme blocks production of an important prothrombotic
agent known as thromboxane A2. Thromboxane A2 causes activation and
aggregation of platelets, which is an early step in thrombosis. Aspirin
is more effective in preventing arterial thrombosis (myocardial infarction,
stroke) than venous thrombosis (deep venous thrombosis, pulmonary embolism).
The explanation for this difference seems to be that platelets play
a larger role in causing arterial thrombosis.
Today, more potent platelet
inhibitors than aspirin are available, but aspirin remains the most
commonly used drug in this category and is still our most cost-effective
antithrombotic drug. Aspirin (either 81 mg or 325 mg daily) is indicated
in the following conditions:
- Unstable angina (acute
coronary syndrome)
- Acute myocardial infarction
- Secondary prevention of
myocardial infarction
- Secondary prevention of
stroke (carotid or primary cerebrovascular disease)
- Prevention of peripheral
arterial thrombosis
