Failure of salicylate to reduce inhibition of human venous prostacyclin in synthesis by conventional dose aspirin.

Ex vivo venous prostacyclin synthesis was measured in 24 patients who received no medication, or a single oral dose of aspirin 300 mg, sodium salicylate, 500 mg, or a combination of sodium salicylate 500 mg followed by aspirin 300 mg 1 1/2 or 3 hr later. Aspirin alone substantially reduced PGI2 synthesis but sodium salicylate alone had no effect. Sodium salicylate administration prior to aspirin did not reverse the inhibitory effect of aspirin on PGI2 synthesis.