Cells lining the gastrointestinal tract release serotonin when damaged by chemotherapy and radiation therapy. This serotonin binds to serotonin receptors on nerves that transmit impulses to the vomiting center within the brain, which in turn stimulates other nerves involved in the vomit reflex. 5-HT3 receptor antagonists prevent serotonin from binding to 5-HT3 receptors in the small intestine thereby reducing the likelihood of nausea and vomiting. The way 5-HT3 receptor antagonists work to prevent postoperative nausea and vomiting is less well understood.
Persons who are using drugs that suppress the immune system (., corticosteroids) are more susceptible to infections than healthy individuals. Chickenpox and measles , for example, can have a more serious or even fatal course in susceptible children or adults using corticosteroids. In children or adults who have not had these diseases or been properly immunized, particular care should be taken to avoid exposure. How the dose, route, and duration of corticosteroid administration affect the risk of developing a disseminated infection is not known. The contribution of the underlying disease and/or prior corticosteroid treatment to the risk is also not known. If a patient is exposed to chickenpox, prophylaxis with varicella zoster immune globulin (VZIG) may be indicated. If a patient is exposed to measles, prophylaxis with pooled intramuscular immunoglobulin ( IG ) may be indicated (see the respective package inserts for complete VZIG and IG prescribing information). If chickenpox or measles develops, treatment with antiviral agents may be considered.