Final answer:
An example of a medication that blocks the effects of substance P, which is useful for preventing delayed vomiting, is ondansetron (Zofran). It functions indirectly by antagonizing serotonin 5-HT3 receptors which influence substance P neurotransmission.
Step-by-step explanation:
The student's question is regarding a substance P receptor blocker that is used for the treatment of delayed vomiting. This mentions a pharmacological intervention for the management of chemotherapy-induced delayed emesis. One of the drugs that block the effects of substance P is ondansetron, which is marketed under the brand name Zofran. Ondansetron is an antiemetic medication that is commonly used to prevent nausea and vomiting associated with cancer chemotherapy, radiation therapy, and surgery. It functions as a selective serotonin 5-HT3 receptor antagonist, which also impacts substance P neurotransmission indirectly.
In terms of delayed vomiting, substance P has been implicated in the mechanism of inducing vomiting by activating neurokinin-1 (NK1) receptors in the brain and gastrointestinal tract. Ondansetron is effective in blocking these receptors and preventing delayed-phase emesis, which typically occurs more than 24 hours after chemotherapy. Although ondansetron is not a direct substance P receptor blocker, the regulation of NK1 receptor activity is significant in managing delayed vomiting. Hence, a potent NK1 receptor antagonist would be an example of a substance P receptor blocker with clinical utility in treating delayed vomiting.