Background and objective: Recent evidence indicates that platelet function may recover more rapidly after cessation of aspirin therapy than previously thought. The present study evaluated the effect of aspirin on platelet function using platelet aggregometry in healthy individuals and in aspirin-treated patients scheduled for surgery.
Methods: Platelet aggregation in response to arachidonic acid, epinephrine, and adenosine diphosphate was determined in 14 male volunteers during and after 10 days' aspirin administration (100 mg) and in 58 aspirin-treated patients during intake, on days 3, 4 or 6 after drug cessation, and on day 10 after drug cessation, prior to elective surgery. Urine thromboxane (11-dehydro-thromboxane B2) concentrations were also measured.
Results: Platelet aggregation in response to arachidonic acid and epinephrine was significantly decreased in both volunteers and patients during aspirin administration. The aggregation normalized within 3 days of aspirin cessation in the volunteers and within 4-6 days in the patients. Urine concentration of 11-dehydro-thromboxane B2 was about three times lower with aspirin treatment than without, although in two patients concentrations were higher with aspirin.
Conclusion: Platelet aggregometry with arachidonic acid is a sensitive test for the evaluation of the effects of aspirin on platelet function. In most aspirin-treated patients, platelet function recovers 4 days after drug cessation, although the process is sometimes prolonged. Therefore, the time of aspirin cessation before scheduled surgery should be determined individually.