Palonosetron-d3 is intended for use as an internal standard for the quantification of palonosetron (Item No. 16752) by GC- or LC-MS. Palonosetron is an antagonist of the serotonin (5-HT) receptor subtype 5-HT3 (Ki = 0.04 nM).1 It is selective for 5-HT3 over 5-HT1A, 5-HT1D, 5-HT2A, and 5-HT2C receptors (Kis = ≥15.85 μM for all), as well as a panel of additional neurotransmitter receptors. Palonosetron inhibits 5-HT-induced contraction in isolated guinea pig ileum. It inhibits cisplatin-induced emesis in ferrets (ID50 = 1.1 μg/kg, i.v.) as well as emesis induced by cisplatin (Item No. 13119), dacarbazine (Item No. 21877), actinomycin D (Item No. 11421), and mechlorethamine in dogs (ID50s = 1.9, 4.1, 4.9, and 4.4 μg/kg, respectively).2 Formulations containing palonosetron have been used in the treatment of postoperative or chemotherapy-induced nausea and vomiting.WARNING This product is not for human or veterinary use.