The absorption of acetylsalicylic acid from an enteric-coated formulation and the inhibition of thromboxane formation.

To compare conventional (CT) and enteric-coated (ECT) tablets of acetylsalicylic acid (ASA) six healthy adult subjects ingested one 0.5-g tablet of these formulations daily for fifteen days in a cross-over study. Significant amount of ASA was detected in peripheral blood of every subject after the ingestion of CT or ECT. The rate of absorption of ASA was faster and its peak plasma concentration was higher after the ingestion of CT. The formation of thromboxane B2 (TXB2) decreased during blood clotting concomitantly with the absorption of ASA from both formulations. The formation of TXB2 was equally and completely inhibited by CT and ECT as it decreased to 1% of the control value one day after the first dose. During treatment with a single daily dose of 0.5 g of CT or ECT, the serum level of TXB2 remained at this low level and returned to the control level gradually in two weeks after the last dose. The present study indicates that significant amount of unchanged ASA is absorbed also from ECT and that the formation of TXB2 is equally and completely inhibited with a 0.5-g daily dose of both formulations.