Bioavailability of acetylsalicylic acid and salicylic acid from rapid-and slow-release formulations, and in combination with dipyridamol.
Acetylsalicylic acid (ASA) is a strong, irreversible inhibitor of platelet aggregation, but loses this activity following first-pass deacetylation to salicylic acid (SA). In order to compare the bioavailability of unchanged ASA from rapid- and slow-release formulations, the single-dose concentration profiles of ASA and SA were studied in healthy volunteers following intake of two different rapid-release (conventional and effervescent tablets) and three different slow-release (microencapsulated ASA in tablets and in capsules, and enteric-coated tablets) formulations of ASA, and of one slow-release formulation of sodium salicylate. Since anti-platelet therapy with ASA is often combined with dipyridamol, the influence of this drug was also examined. The concentrations of ASA and SA were measured by high-pressure liquid chromatography. While the bioavailability of SA from the 5 ASA formulations was essentially equal and similar to that of the salicylate formulation, the bioavailability and peak concentrations of ASA appeared to be the much greater after rapid-release than after slow-release formulations. Indeed, ASA was only rarely detected in systemic blood following intake of slow-release ASA. Co-administered dipyridamol did not significantly influence the kinetics of ASA or SA. It appears that rapid-release formulations of ASA should be prefered in anti-platelet therapy, either alone or in combination with dipyridamol.
D000328:Adult; D001241:Aspirin / Q000008:administration & dosage* / Q000378:metabolism; D001682:Biological Availability; D003692:Delayed-Action Preparations; D004176:Dipyridamole / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D012459:Salicylates / Q000008:administration & dosage* / Q000378:metabolism; D020156:Salicylic Acid
D003692:Delayed-Action Preparations; D012459:Salicylates; D004176:Dipyridamole; D020156:Salicylic Acid; D001241:Aspirin