Platelet aggregation and plasma levels of acetylsalicylic acid in stroke patients on long-term treatment with an enteric-coated aspirin formulation

Acidosis, magnesium and acetylsalicylic acid: effects on thrombin

Thrombin, an enzyme from the hydrolase family, is the main component of the blood coagulation system. In ischemic stroke it acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin forming blood clots in the brain. It has been found to phosphoresce at room temperature in the millisecond and microsecond ranges. The phosphorescence of thrombin was studied under physiological conditions, in acidosis (decrease of pH from 8.0 to 5.0) and on the addition of salts (magnesium sulfate and sodium chloride) and of acetylsalicylic acid, and its connection with thrombin function is discussed. Acidosis significantly increased the internal dynamics of thrombin. We propose that lactate-acidosis plays a protective role in stroke, preventing the formation of clots. The addition of NaCl and MgSO(4) in different concentrations increased the internal dynamics of thrombin. Also, the addition of MgSO(4) decreased thrombin-induced platelet aggregation. However, magnesium sulfate and acetylsalicylic acid in the therapeutic concentrations used for treatment of ischemic stroke had no effect on thrombin internal dynamics. The data obtained will help to elucidate the conformational stability of thrombin under conditions modulating lactate-acidosis and in the presence of magnesium sulfate.

High-dose acetylsalicylic acid after cerebral infarction. A Swedish Cooperative Study

Within 3 weeks of the event, 505 patients with cerebral infarction, minor or major stroke, were randomly assigned to treatment with acetylsalicylic acid (ASA) 1.5 g/day or placebo in a double-blind clinical trial with a follow-up of 2 years in all patients. Primary events were considered to be recurrent stroke or death; secondary events, myocardial infarction and transient ischemic attack. There was no difference in stroke recurrence rate in the ASA and placebo groups (12 and 13%, respectively), nor was there any significant difference in the rate of recurrent stroke or death, first event counted (23% in the ASA and 22% in the placebo group). The risk of transient ischemic attack and myocardial infarction was not reduced in the ASA group. In the present study there was no prophylactic effect of high-dose ASA after cerebral infarction. A compilation of the major trials of ASA after transient ischemic attack and cerebral infarction is presented.