Comparative Bioavailability of Enteric-Coated Aspirin Preparations

Abstract

A three-way crossover study was conducted in nine healthy subjects to compare the bioavailability of one uncoated and two enteric-coated aspirin products after the administration of a single 650-mg dose of each preparation. Urine was collected at various intervals for 24 hours after drug administration and assayed for total salicylic acid content as an indicator of bioavailability. There were statistically significant differences among the three products in the amount of salicylic acid appearing in the urine, both for specific collection intervals and for cumulative (24-hour) excretions. Greater (p < 0.001) amounts of urinary salicylic acid were found in the first three hours after uncoated aspirin treatment than after enteric-coated aspirin administration. After 24 hours, equivalent amounts of salicylic acid were found following treatment with uncoated aspirin and one of the enteric-coated preparations. The absorption of aspirin from enteric-coated preparations is markedly delayed when compared to that from an uncoated product.