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The basis for aspirin dosage in stroke prevention
1Department of Medicine, University of Queensland, Brisbane.
Insights
Aspirin can prevent stroke by inhibiting platelet aggregation. However, optimal dosing is crucial, as higher doses may hinder stroke prevention by affecting endothelial function. Rapid-release aspirin is recommended for stroke prevention.
Area of Science:
- Cardiovascular Medicine
- Pharmacology
- Neurology
Background:
- Stroke often results from platelet aggregation on damaged arterial endothelium.
- Aspirin inhibits platelet aggregation by blocking thromboxane A2 formation.
- Aspirin also inhibits prostacyclin, an anti-aggregatory substance produced by the endothelium.
Purpose of the Study:
- To determine the optimal aspirin dosage and formulation for stroke prevention.
- To balance aspirin's effects on platelet aggregation and endothelial function.
- To investigate the pharmacokinetics of aspirin for stroke prevention.
Main Methods:
- Theoretical modeling of aspirin's effects on platelets and endothelium.
- Analysis of plasma aspirin concentration-time profiles in humans.
- Evaluation of platelet aggregability in response to varying aspirin concentrations.
Main Results:
- Aspirin's effect on platelets is long-lasting, while its effect on endothelium is transient.
- Rapid-release aspirin formulations achieve necessary plasma concentrations more effectively than slow-release ones.
- A peak plasma aspirin concentration of approximately 1.2 mg/L is required to inhibit platelet aggregability.
Conclusions:
- Pulsatile administration of rapid-release aspirin at intervals maintaining platelet inhibition offers the best stroke prevention strategy.
- Careful aspirin dosing is essential to maximize therapeutic benefits while minimizing potential adverse effects on endothelial function.
- Achieving specific plasma aspirin concentrations is key for effective stroke prevention.
Abstract:
Many strokes are thought to develop as a consequence of platelet aggregation on areas of arterial endothelial damage, with subsequent embolism or thrombus formation. Aspirin prevents platelet adhesion and aggregation by inhibiting the formation of thromboxane A2 by platelets. This suggests that aspirin could be used to prevent stroke. However aspirin also inhibits endothelial formation of the anti-aggregatory substance prostacyclin, though probably only in a slightly higher dose than that just capable of inhibiting platelet aggregation. Consequently, too high an aspirin dose may defeat its purpose. The effect of aspirin on platelets lasts for as long as they survive, whereas the effects of aspirin on endothelium are shorter. Theoretical considerations suggest that aspirin, given in brief pulses just to reach platelet inhibitory concentrations in plasma, and administered at the maximum interval that will maintain inhibition of platelet aggregation, should offer the most favourable balance between altered platelet and altered endothelial function from the viewpoint of stroke prevention. Data are presented showing that rapid rather than slow or delayed release aspirin preparations are necessary to achieve suitable plasma aspirin concentration-time profiles in humans, and that a peak plasma aspirin concentration of around 1.2 mg/L is necessary in vivo to inhibit aggregability of previously untreated platelets.