PALONOSETRON IS A 5-HT3 RECEPTOR ANTAGONIST WITH A STRONG BINDING AFFINITY FOR THIS RECEPTOR AND LITTLE OR NO AFFINITY FOR OTHER RECEPTORS.
CANCER CHEMOTHERAPY MAY BE ASSOCIATED WITH A HIGH INCIDENCE OF NAUSEA AND VOMITING, PARTICULARLY WHEN CERTAIN AGENTS, SUCH AS CISPLATIN, ARE USED. 5-HT3 RECEPTORS ARE LOCATED ON THE NERVE TERMINALS OF THE VAGUS IN THE PERIPHERY AND CENTRALLY IN THE CHEMORECEPTOR TRIGGER ZONE OF THE AREA POSTREMA. IT IS THOUGHT THAT CHEMOTHERAPEUTIC AGENTS PRODUCE NAUSEA AND VOMITING BY RELEASING SEROTONIN FROM THE ENTEROCHROMAFFIN CELLS OF THE SMALL INTESTINE AND THAT THE RELEASED SEROTONIN THEN ACTIVATES 5-HT3 RECEPTORS LOCATED ON VAGAL AFFERENTS TO INITIATE THE VOMITING REFLEX.