Aloxi
Meaning of Aloxi: An anti-sickness injection that holds onto its receptor far longer than the older drugs in the same class.
Definition of Aloxi
Aloxi is a brand of palonosetron, a drug given to prevent nausea and vomiting caused by chemotherapy. It blocks 5-HT3 receptors, the docking points for serotonin on the nerves that set off the vomiting reflex. Palonosetron binds those receptors more tightly and for far longer than the earlier drugs of its class, so a single dose covers several days.
How does blocking serotonin prevent sickness?
Chemotherapy damages the cells lining the small bowel. Among them are enterochromaffin cells, which hold large stores of serotonin, and injury makes them dump that store into the surrounding tissue. Serotonin lands on 5-HT3 receptors sitting on the endings of the vagus nerve in the gut wall. The nerve carries the signal to the brainstem, and the vomiting reflex follows. Palonosetron occupies those receptors first, so the serotonin arrives to find the docking points already taken.
How does it differ from the older drugs of its class?
| Ondansetron and granisetron | Palonosetron | |
|---|---|---|
| Time in the body | Hours | Around a day and a half |
| Grip on the receptor | Binds and releases | Binds far more tightly |
| Effect after binding | Blocks the receptor | Also pulls receptors inside the cell |
| Delayed sickness | Limited effect | Useful effect |
What kinds of sickness does it address?
Chemotherapy-induced sickness splits into two phases. Acute sickness begins within hours and is driven mainly by the serotonin surge from the gut. Delayed sickness starts a day or more later and is driven instead by substance P acting at neurokinin-1 receptors in the brainstem. A drug in this class handles the acute phase well; the long duration of palonosetron extends useful cover into the delayed phase, though it does not replace a neurokinin-1 blocker. For strongly emetogenic regimens, an antiemetic plan usually combines a 5-HT3 receptor antagonist, a neurokinin-1 blocker and a corticosteroid.
What effects does it have?
Headache and constipation are the common ones across the whole class, and constipation follows from the fact that serotonin also drives normal bowel movement. Effects on the heart's electrical recovery time are recognized for the group, and palonosetron is generally regarded as having less influence there than some of the older agents.
Also known as
Used in a sentence
Aloxi was given before the infusion as part of the antiemetic regimen.
Good to know
Palonosetron differs from earlier drugs in the class by how long it remains bound rather than by acting on a different receptor, which is what extends its cover into delayed sickness.