The effects of aspirin on the platelet function of healty volunteers and of patients with occlusive arterial vascular disease.

Aspirin inhibits platelet aggregation through an irreversible and competitive
binding with the enzyme cyclo-oxygenase (COX). Cyclooxygenase is required for
thromboxane synthesis, which is a strong vasoconstrictor and platelet
triggerer. Through these mechanisms the use aspirin in patients with
cardiovascular disease leads to a significant risk reduction. However, not all
patients seem to benefit from the use of aspirin. An important part of the
patients seem to have high platelet activity despite the use of aspirin. This
is also called laboratory aspirin resistance, which can be identified by the
use of several platelet function tests. Previous studies have shown that in
cardiology patients with laboratory aspirin resistance, there is an increased
cardiovascular risk. In case of ischemic stroke, this correlation isn't proven
yet.

Objective of the study is to investigate the effects of aspirin on the platelet
function of healthy volunteers and of patients with ischemic stroke. In another
part of the study, we will investigate whether or not the effects of aspirin on
the platelets of patients without recurrent disease differs from the effects of
patients with recurrent disease despite the use of aspirin. Next to standard
platelet function tests we will also include the thrombinegeneration
measurement.

It is an intervention study with 12 healty volunteers. They have to take
carbasalate calcium 100mg daily during 7 days. On day 0 and dag 6 of the study,
subjects have to come to the hospital, where bloods will be drawn before and
after the ingestion of carbasalate calcium in order to study the effects of
carbasatale calcium of the platelet function.
Another part of the study will be a pilot study with 24 patients with an
ischemic stroke based on large vessel disease in the medical history. The event
must have taken place between 01-07-01 and 01-07-06. All patients are treated
with carbasalate calcium 100mg daily. 12 of the 24 patients have recurrent
disease despite carbasalate calcium and 12 of the 24 patients don't have
recurrent disease. Patients have to come to the hospital once: bloods will be
drawn before and after the ingestion of carbasalate calcium in order to
investigate the effects of carbasalate calcium on the platelet function.

population A
100 mg of carbasalate calcium daily, during a period of 7 days
2x2 venapuntions

Population B
2 venapunctions
no additional medical treatment

Population A
The subjects will be treated with carbasalate calium 100mg daily during a
period fof 7 days. The risk is minimal and equal to the risks of the use of
carbasalate calcium. In order to minimalise the risks we will exclude
volunteers with any knows (relative) contra-indication for aspirin.
The subjects will have to come to the hospital on day 0. In addition, blood
will be obtained by 2 times a venapuntion (once before and once 2.5 hours after
the intake of carbasalate calcium 100mg). The same procedure will be repeated
on day 6.

Population B
Patients from population B are already treated with carbasalate calcium 100mg
daily. The medical treatment will remain the same during and after the study.
These subjects will have to come to the hospital once. In addition blood will
be obtained by 2 times a venapunction (once before and once after the intake of
carbasalate calcium).