Pathophysiology of chemotherapy induced nausea and vomiting

Chemotherapy-induced nausea and vomiting is classified in three stages:

• acute - within first 24 hours of administration of chemotherapy
  • believed that the chemotherapy causes enterochromaffin cells in the upper gastrointestinal tract to release serotonin, which acts locally on serotonin type 3 (5HT3) - receptors, triggering afferent impulses to the vomiting centre in the medulla. Selective 5HT3-receptor antagonists (such as ondansetron) appear to work by blocking this pathway
• delayed - occurring more than 24 hours after administration and lasting for up to 5-7 days
  • no evidence that it is associated with release of serotonin and the underlying mechanism is not known
  • there is however evidence to suggest that release of a neuropeptide, substance P (which acts by binding to a specific neuroreceptor, neurokinin 1), may be important in the genesis of chemotherapy-induced emesis, particularly in the delayed phase
• anticipatory
  • believed to represent a conditioned response

Reference:

1. Drug and Therapeutics Bulletin 2005; 43 (8):57-61.