Palonosetron is a selective antagonist of 5-HT3 receptor with strong affinity, with no affinity or low affinity to other receptors. The 5-HT3 receptor is located in the central and surrounding vagus nerve endings of the emetic chemotherapeutic receptor in the final region of the medulla oblongata. Chemotherapy agents stimulate the release of 5-HT by small intestinal pheochromotropic cells, which in turn activate the 5-HT3 receptor of the vagafferent nerve, producing the vomiting reflex.