WBR0727
| Author | [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology |
| Sub Category | SubCategory::Oncology |
| Prompt | [[Prompt::A 52-year-old man, with a history of heavy tobacco use, presents to the physician's office for dyspnea and weight loss. Following appropriate work-up, he is diagnosed with limited stage small cell lung carcinoma (SCLC). The patient is then scheduled to undergo chemotherapy sessions. Before the intravenous (IV) administration of the chemotherapeutic agent, the physician prescribes a prophylactic medication to prevent the occurrence of nausea or vomiting during chemotherapy administration. What is the most likely mechanism of action of the administered agent to manage the patient's nausea and vomiting?]] |
| Answer A | AnswerA::Antagonist to serotonin receptor |
| Answer A Explanation | AnswerAExp::Ondansetron is a serotonin (5-HT3) receptor antagonist. |
| Answer B | AnswerB::Antagonist to dopamine receptor |
| Answer B Explanation | AnswerBExp::Metoclopramide, also an antiemetic, is a dopamine (D2) receptor antagonists. However, metoclopramide is not as effective as ondansetron for chemotherapy-induced emesis. |
| Answer C | AnswerC::Agonist to serotonin receptor |
| Answer C Explanation | AnswerCExp::Ondansetron is an antagonist to serotonin receptor, not an agonist. |
| Answer D | AnswerD::Agonist to dopamine receptor |
| Answer D Explanation | AnswerDExp::Ondansetron is not a dopamine receptor agonist. |
| Answer E | AnswerE::Antagonist to serotonin and dopamine receptors |
| Answer E Explanation | AnswerEExp::Ondansetron is a serotonin receptor antagonist. It has no major effect on dopamine receptors. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Ondansetron is a 5-hydroxytryptamine (5-HT3) receptor antagonist or a serotonin receptor antagonist. It has a powerful central antiemetic activity that is very effective against nausea and vomiting associated with chemotherapy and is usually given prophylactically. However, it might also be administered in other conditions, such as severe hyperemesis gravidarum among pregnant women.
It is generally well-tolerated by patients. The most common adverse effects of ondansetron are: headache, constipation or diarrhea, sedation, and small increases in liver function tests that are usually self-limited. Ondansetron is almost totally eliminated by the liver with minimal amounts retrieved intact in the urine. Generally, its half life is 3-4 hours, but might vary according to age. Half-life is shorter among children and more prolonged among older patients. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Ondansetron, WBRKeyword::5HT3, WBRKeyword::5-HT3, WBRKeyword::Cancer, WBRKeyword::SCLC, WBRKeyword::Small cell lung cancer, WBRKeyword::Small cell lung carcinoma, WBRKeyword::Chemotherapy, WBRKeyword::Nausea, WBRKeyword::Vomiting, WBRKeyword::Side effect, WBRKeyword::Side, WBRKeyword::Effect, WBRKeyword::Adverse, WBRKeyword::Reaction, WBRKeyword::Serotonin, WBRKeyword::Receptor, WBRKeyword::Antagonist, WBRKeyword::Antagonism, WBRKeyword::Mechanism, WBRKeyword::Action, WBRKeyword::Dopamine, WBRKeyword::Drug, WBRKeyword::Metoclopramide, WBRKeyword::Antiemetic, WBRKeyword::Antiemesis, WBRKeyword::Adverse reaction, WBRKeyword::Adverse drug reaction |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |