GYKI-46903 is a non-competitive antagonist for 5-HT3 receptors. In displacement studies, the pIC50 values of GYKI-46903 against [3H]granisetron binding to rat cerebral cortex membranes were 6.91. GYKI-46903, when administered by intravenous infusion, antagonized the decrease in heart rate evoked by serotonin (Bezold-Jarisch reflex) in anaesthetized rats, and the maximal reversal was less than 50%.
