WBR0932
Author | PageAuthor::William J Gibson |
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Exam Type | ExamType::USMLE Step 1 |
Main Category | MainCategory::Pharmacology |
Sub Category | SubCategory::Pulmonology |
Prompt | [[Prompt::A drug called Ro 47-0203 is being evaluated for the treatment of pulmonary hypertension. Scientists find that in an in-vitro assay measuring the isometric tension of pig aortic rings, Ro 47-0203 is able to induce a potent rightward shift of the concentration response curve to endothelin-1. However, it has no additional effect when used concurrently with a selective endothelin A antagonist. Which of the following drugs does Ro 47-0203 most likely refer to?]] |
Answer A | AnswerA::Bosentan |
Answer A Explanation | AnswerAExp::Correct: Bosentan is a competitive antagonist of endothelin-1 receptors that is used to treat pulmonary hypertension. |
Answer B | AnswerB::Diltiazem |
Answer B Explanation | AnswerBExp::Incorrect: Diltiazem is a nondihydropyridine calcium channel blocker that prolongs survival in patients with pulmonary hypertension. Diltiazem does not bind endothelin receptors. |
Answer C | AnswerC::Treprostinil |
Answer C Explanation | AnswerCExp::Incorrect: Treprostinil is a synthetic analog of prostacyclin (PGI2). While treprostinil has been shown to improve symptoms for a subset of patients with pulmonary hypertension, it does not act through endothelin receptors. |
Answer D | AnswerD::Sildenafil |
Answer D Explanation | AnswerDExp::Incorrect: Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor that can increase vasodilation in response to nitric oxide, thereby improving pulmonary hypertension. Sildenafil is most commonly used to treat erectile dysfunction. |
Answer E | AnswerE::Riociguat |
Answer E Explanation | AnswerEExp::Incorrect: Riociguat is a soluble guanylate cyclase stimulator that increases vessel reactivity to nitric oxide and can thereby treat pulmonary hypertension. |
Right Answer | RightAnswer::A |
Explanation | [[Explanation::The drug described is able to right-shift the concentration response curve to endothelin, meaning that higher doses of endothelin-1 are required to achieve the same response in the presence of Ro47-0203. Endothelins are the most potent vasoconstrictors known. Because Ro47-0203 acts antagonistically to endotelin-1, we can reason that it is an enothelin receptor antagonist. The only endothelin receptor antagonist among the answer choices is Bosentan.
Educational Objective: Bosentan is a competitive antagonist of endothelin-1 receptors that is used to treat pulmonary hypertension. References: First Aid 2012 page 577 First Aid 2013 page 564 Véniant M, Clozel JP, Hess P, Clozel M. Endothelin plays a role in the maintenance of blood pressure in normotensive guinea pigs. Life Sci. 1994;55(6):445-54. |
Approved | Approved::Yes |
Keyword | WBRKeyword::Pulmonary hypertension, WBRKeyword::Endothelin |
Linked Question | Linked:: |
Order in Linked Questions | LinkedOrder:: |