Molecule

Drug Groups

approved; investigational

Description

Palonosetron (INN, trade name Aloxi) is a 5-HT3 antagonist used in the prevention and treatment of chemotherapy-induced nausea and vomiting (CINV). It is the most effective of the 5-HT3 antagonists in controlling delayed CINV nausea and vomiting that appear more than 24 hours after the first dose of a course of chemotherapy and is the only drug of its class approved for this use by the U.S. Food and Drug Administration. As of 2008, it is the most recent 5-HT3 antagonist to enter clinical use. [wikipedia]

Indication

For the prevention of acute and delayed nausea and vomiting associated with initial and repeat courses of moderately emetogenic cancer chemotherapy, as well as prevention of acute nausea and vomiting associated with highly emetogenic cancer chemotherapy. Also used for the prevention of postoperative nausea and vomiting for up to 24 hours post operation.

Pharmacology

Palonosetron is an antinauseant and antiemetic agent indicated for the prevention of nausea and vomiting associated with moderately-emetogenic cancer chemotherapy and for the prevention of postoperative nausea and vomiting. Palonosetron is a highly specific and selective serotonin 5-HT₃ receptor antagonist that is pharmacologically related to other 5-HT₃ receptor antagonists, but differs structurally. Palonosetron has a high affinity for 5-HT₃ receptors, but has little to no affinity for other receptors. The serontonin 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 suggested that chemotherapeutic agents release serotonin from the enterochromaffin cells of the small intestine by causing degenerative changes in the GI tract. The serotonin then stimulates the vagal and splanchnic nerve receptors that project to the medullary vomiting center, as well as the 5-HT3 receptors in the area postrema, thus initiating the vomiting reflex, causing nausea and vomiting.

Toxicity

A single intravenous dose of palonosetron at 30 mg/kg (947 and 474 times the human dose for rats and mice, respectively, based on body surface area) was lethal to rats and mice. The major signs of toxicity were convulsions, gasping, pallor, cyanosis and collapse.

Affected Organisms

Biotransformation

Hepatic (50%), primarily CYP2D6-mediated, although CYP3A4 and CYP1A2 are also involved.

Absorption

Low oral bioavailability.

Half Life

Approximately 40 hours

Protein Binding

62%

Elimination

After a single intravenous dose of 10 mcg/kg [14C]-palonosetron, approximately 80% of the dose was recovered within 144 hours in the urine

Distribution

* 8.3 ± 2.5 L/kg

Clearance

* 160 +/- 35 mL/h/kg

References

External Links