Granisetron is a potent, selective antagonist of 5-HT3 receptors. The antiemetic activity of the drug is brought about
through the inhibition of 5-HT3 receptors present both centrally (medullary chemoreceptor zone) and peripherally (GI
tract). This inhibition of 5-HT3 receptors in turn inhibits the visceral afferent stimulation of the vomiting center,
likely indirectly at the level of the area postrema, as well as through direct inhibition of serotonin activity within
the area postrema and the chemoreceptor trigger zone.