Paloxi (palonosetron hydrochloride) is an antiemetic and antinauseant agent. It is a serotonin subtype 3 (5-HT3) receptor antagonist with a strong binding affinity for this receptor. Chemically, palonosetron hydrochloride is: (3aS)-2-[(S)-1-Azabicyclo [2.2.2]oct-3-yl]-2,3,3a,4,5,6-hexahydro-1oxo-1Hbenz[de]isoquinoline hydrochloride. The empirical formula is C19H24N2O.HCl, with a molecular weight of 332.87. Palonosetron hydrochloride exists as a single isomer and has the following structural formula:
Palonosetron hydrochloride is a white to off -white crystalline powder. It is freely soluble in water, soluble in propylene glycol, and slightly soluble in ethanol and 2 -propanol.
Paloxi injection is a sterile, clear, colorless, non-pyrogenic, isotonic, buffered solution for intravenous
administration. Each 5-ml vial of Paloxi injection contains 0.25 mg palonosetron base as hydrochloride, 207.5 mg mannitol, edetate disodium dihydrate, trisodium citratedihydrate, citric aci d monohydrate, and water for injection for intravenous administration. The pH of the solution is 4.5 to
Mechanism of Action
Palonosetron is a 5-HT3 receptor antagonist with a strong binding affinity for this receptor and litt le 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 s erotonin then activates 5-HT3 receptors located on vagal afferents to initiate the vomiting reflex.