Rapid recovery of in vivo prostacyclin formation after inhibition by aspirin

Summary The effect of aspirin on the in vivo formation of prostacyclin and thromboxane A₂ in normal healthy individuals was studied by measuring the urinary excretion of 2,3-dinor-6-keto-PGF₁ and 2,3-dinor-TxB₂ by gas chromatography-mass spectrometry. Administration of 500 mg aspirin twice daily caused a sustained reduction in the excretion of 2,3-dinor-TxB₂ to 10–15% of the predose value, while the excretion of 2,3-dinor-6-keto-PGF₁ was reduced for only about 3 hours after the aspirin dose. The data demonstrate a considerable difference in the inhibitory effect of aspirin on the in vivo synthesis of thromboxane A₂ and prostacyclin.