The beneficial effect of
aspirin in different situations of
coronary artery disease has been clearly demonstrated, but prescription remains empirical due to the lack of phase II trials and the incompletely understood mechanism of action. Since the ISIS-2 study was published in 1988,
aspirin is indicated in the acute phase of
myocardial infarction as mortality can be reduced by 20% and the rate of reocclusions reduced. The beneficial effect of
aspirin in
unstable angina has also been demonstrated with a reduction of more than 50% in the combined incidence of mortality and
myocardial infarction.
Stable angina is an ideal application for low-dose
aspirin with an improvement in combined incidence of
myocardial infarction and
sudden death of 34%. The question of dose remains open. When prescribed for primary or
secondary prevention,
aspirin should be given at low-doses (50-100 mg/d) in a long-term regimen. The dose should be examined differently for treatment of acute thrombotic events including
infarction and
unstable angina. Doses above 250 mg/d with an initial dose of 500 mg to 1 g are recommended followed by a relay with 50 to 100 mg/d. Irreversible dose-dependent inhibition of platelet
cyclooxygenase by
aspirin is nearly total for a single dose of 100 mg. The effect is cumulative for smaller doses and since the anucleated platelets cannot resynthesize the
enzyme only new platelet can recover enzymatic activity. The duration of the effect thus is a function of normal platelet turn-over (8 days). Currently,
aspirin is indicated in all coronary artery patients and should be discussed for "potential" patients i.e. as primary prevention in healthy subjects at risk of
coronary artery disease although the threshold of risk requiring prescription remains to be clearly determined.