A pharmacokinetic approach to the establishment of biopharmaceutic characteristics of different acetylsalicylic acid formulations in man

A comparison of two doses of aspirin (30 mg vs. 283 mg a day) in patients after a transient ischemic attack or minor ischemic stroke

BACKGROUND

Aspirin is known to improve the outcome of patients who have had a cerebral transient ischemic attack, but the optimal dose of aspirin remains uncertain. Experimental evidence indicates that 30 mg of aspirin daily alters platelet aggregation more favorably than the 300-mg dose currently used in patients after transient ischemic attack or minor ischemic stroke.

METHODS

We assessed the effects of two doses of a water-soluble preparation of acetylsalicylic acid, or aspirin (30 mg vs. 283 mg a day), on the occurrence of death from all vascular causes, nonfatal stroke, or nonfatal myocardial infarction in a double-blind, randomized, controlled clinical trial in patients who had had a transient ischemic attack or minor stroke. A total of 3131 patients participated in the study. The mean follow-up was 2.6 years.

RESULTS

In the group assigned to receive 30 mg of aspirin, the frequency of death from vascular causes, nonfatal stroke, or nonfatal myocardial infarction was 228 of 1555 (14.7 percent), as compared with 240 of 1576 (15.2 percent) in the group assigned to receive 283 mg. The age- and sex-adjusted hazard ratio for the group receiving the lower dose was 0.91 (95 percent confidence interval, 0.76 to 1.09). There were slightly fewer major bleeding complications in the 30-mg group than in the 283-mg group (40 vs. 53), and significantly fewer reports of minor bleeding (49 vs. 84). Fewer patients receiving 30 mg of aspirin reported gastrointestinal symptoms (164 vs. 179) and other adverse effects (73 vs. 90).

CONCLUSIONS

Our data indicate that 30 mg of aspirin daily is no less effective in the prevention of vascular events than a 283-mg dose in patients with a transient ischemic attack or minor stroke, and has fewer adverse effects.

Mechanisms of cell association of some non-steroidal anti-inflammatory drugs with isolated leucocytes

In the present study the degree and the mode of association of the radiolabelled drugs acetylsalicylic acid, sodium salicylate, and sodium benzoate with leucocytes were studied in view of the hypothesis that leucocytes are target cells for the anti-inflammatory activity of drugs. The overall association rate of acetylsalicylic acid is larger than that of sodium salicylate and sodium benzoate at 37 degrees, but smaller at 4 degrees. The ratio of the intracellular to the extracellular concentration varied between 1 and 2 for sodium salicylate and sodium benzoate, and between 3 and 6 for acetylsalicylic acid. The intracellular concentrations of these drugs were comparable in red blood cells and polymorphonuclear leucocytes, but lower in mononuclear leucocytes. The association of acetylsalicylic acid and sodium salicylate is markedly increased when the extracellular pH decreases. Lysis of cells decreases the association of acetylsalicylic acid and enhances the association of sodium salicylate and benzoate at 37 degrees twofold. It is suggested that the association of these drugs with leucocytes comprises binding to the membrane and uptake of undissociated species. Phorbol myristate acetate extensively inhibits the intracellular concentration of acetylsalicylic acid, while this inflammatory stimulus tends to increase the intracellular concentration of sodium salicylate. The major metabolites of salicylate enhance cell association of acetylsalicylic acid and salicylic acid. In conclusion, these findings indicate that the tested benzoic acid-like drugs associate with leucocytes in vitro to some extent and that environmental differences, e.g. pH, lysed cells, inflammatory stimuli and metabolites, may determine in vivo the degree of accumulation.