ABSORPTION KINETICS OF LOW-DOSE ASPIRIN IN PATIENTS WITH EVOLVING ACUTE MYOCARDIAL-INFARCTION

Administration of aspirin in patients with evolving acute myocardial i nfarction (AMI) has been associated with reduced short and long term m ortality. Neither the mechanism of the beneficial effect of aspirin no r the kinetics of its absorption in these patients have been determine d. We studied the pharmacokinetics of rapid release aspirin (100mg) in 20 patients with evolving AMI. The peak creatine kinase (CK) level wa s 2452 +/- 416 (SEM) IU/L. Thrombolytic therapy was utilised in 16 pat ients. Aspirin was administered 5.8 +/- 0.8 hours after onset of pain (range 1.5 to 11 hours). The peak aspirin concentration was 939 +/- 13 7 mu g/L, occurring 0.71 +/- 0.11 hours (range 0.3 to 2.0 hours) after aspirin ingestion. There was considerable interindividual variability in aspirin absorption, which was not significantly correlated with ag e, sex, bodyweight, time after onset of pain, thrombolytic therapy, in farct site or peak CK level. However, the maximal aspirin concentratio n was lower and time to peak concentration greater than that observed in a previous analogous study in normal subjects. We conclude that in patients with evolving AMI, aspirin absorption is variably reduced and delayed. The bases for this delay, and for interpatient variability, were not apparent from correlations with routinely measured clinical p arameters. Variability in aspirin absorption suggests that oral admini stration of 100mg of aspirin may not be ideal as the first dose in pat ients with evolving AMI.