Thromboxane synthase inhibition: "endoperoxide shunt phenomenon" does not occur in healthy humans in vivo.

The effects of the thromboxane synthase inhibitor CGS13080 on the in vivo synthesis of thromboxane and prostacyclin were determined in six healthy volunteers. Two different doses (0.08 and 0.25 mg/kg x h) were infused for six hours under strictly controlled conditions and 2,3-dinor-TxB2 and 2,3-dinor-6-keto-PGF1 alpha were measured in urine using gaschromatography--mass spectrometry. The in vivo synthesis of thromboxane was inhibited by 80-75% while there was no effect on the in vivo prostacyclin synthesis.