5HT3-receptor antagonists

Ondansetron is one of a group of 5HT3-receptor antagonists currently available in the UK, which also includes granisetron, tropisetron, dolasetron and palonosetron. Dexamethasone is a corticosteroid. Ranitidine is a histamine-2 (H2)-receptor antagonist. 

Prophylactic administration of antiemetics is essential in any patient receiving FOLFOX chemotherapy. The combination of oxaliplatin and 5-fluorouracil results in a moderate level of emetogenicity and requires the administration of 5HT3-receptor antagonists and corticosteroid treatment, generally with a dopamine antagonist such as metoclopramide or domperidone. Severe manifestations may have to be managed by delay and/or dose modification of the patient s next cycle of chemotherapy. 

One of the major side-effects of cytotoxic chemotherapy is nausea and vomiting. It is essential therefore to control this with prophylactic antiemetic therapy. A number of agents are currently available and are effective at controlling chemotherapy-induced emesis. The most potent of these are 5HT3-receptor antagonists that include ondansetron, granisetron and palonosetron. 

The use of cytotoxic drugs with a high level of emetogenicity requires the prophylactic administration of a combination of a 5HT3-receptor antagonist and a corticosteroid to prevent the onset of acute nausea and vomiting (i.e. within the first 24 hours). 

There is little evidence supporting the use of 5HT3-receptor antagonists beyond the first 24 hours, and corticosteroids appear to be the most effective component of antiemetic regimens used to prevent delayed nausea and vomiting (American Society of Clinical Oncology et ah, 2006). 

Tropisetron is marketed outside the U.S. as a 5HT3 receptor antagonist for nausea, but it has a7-nicotinic agonist effects in the same concentration range. Tropisetron normalizes P50 inhibition in schizophrenics, with the effect primarily occurring in the nonsmoking subjects (Koike et al., 2005). 

Chemical/Pharmaceutical/Other Class Serotonin 5HT3-receptor antagonist... 

HT3 RECEPTOR ANTAGONISTS [SED-15, 1365 SEDA-31, 575 SEDA-32, 666 SEDA-33, 744]... 

Managemeut of adverse drug reactious 5HT3 receptor antagonists The addition of ondansetron and ketorolac to fentanyl was associated with less nausea and vomiting and dizziness in 135 patients undergoing thyroid surgery [76 ]. 

Azasetron, a potent selective 5HT3 receptor antagonist, is a benzamide derivative that has a different chemical structure and a longer duration of action than other 5HT3 receptor antagonists, such as granisetron, ondansetron, and tropisetron [29 ]. For a comparison of azasetron with ondansetron, see above. 

Although other 5HT3 receptor antagonists (particularly ondansetron) have been previously reported to cause seizures, in this case the role of palonosetron was uncertain. 

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