WBR0755
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| 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::Musculoskeletal/Rheumatology |
| Prompt | [[Prompt::A 55-year-old alcoholic man presents to the physician's office with complaints of excruciating pain in the left great toe. The patient explains that he has been recently having recurrent episodes of the same pain, each episode lasting for a few days. Physical examination is remarkable for erythema and tenderness of the first metatarsophalangeal joint. Work-up is remarkable for elevated blood concentrations of uric acid and C-reactive protein (CRP). The physician prescribes a drug that lacks a purine ring and directly inhibits the conversion of hypoxanthine to xanthine. Which drug has this patient been most likely prescribed?]] |
| Answer A | AnswerA::Allopurinol |
| Answer A Explanation | AnswerAExp::Allopurinol is a xanthine oxidase inhibitor that contains a purine ring. |
| Answer B | AnswerB::Febuxostat |
| Answer B Explanation | AnswerBExp::Febuxostat is a xanthine oxidase inhibitor that lacks a purine ring. |
| Answer C | AnswerC::Probenecid |
| Answer C Explanation | AnswerCExp::Probenecid is a uricosuric that inhibits the reabsorption of uric acid in the proximal convoluted tubule. |
| Answer D | AnswerD::Colchicine |
| Answer D Explanation | AnswerDExp::Colchicine binds and stabilizes tubulin and inhibits polymerization. It impairs chemotaxis and degranulation of leukocytes. |
| Answer E | AnswerE::Pegloticase |
| Answer E Explanation | AnswerEExp::Pegloticase is a pegylated recombinant mammalian uricase that converts urate to allantoin, a soluble and easily excreted compound. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient is presenting with signs and symptoms consistent with gout. Given his alcohol history, the location and asymmetric nature of the joint pain (left great toe), and elevated concentrations of uric acid and CRP, the diagnosis of gouty attack is very likely. Febuxostat is a new non-purine, xanthine oxidase inhibitor that is more potent than allopurinol. In comparison, allopurinol is a xanthine oxidase inhibitor that contains a purine ring. Xanthine oxidase is an enzyme that metabolizes 2 consecutive reactions in the pathway of uric acid degradation. Xanthine oxidase inhibition results in a reduced rate of hypoxanthine conversion to xanthine and similarly, xanthine conversion to plasma uric acid. Educational Objective: Febuxostat is a potent non-purine xanthine oxidase inhibitor indicated for the management of gout. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Gout, WBRKeyword::Gouty attack, WBRKeyword::Febuxostat, WBRKeyword::Allopurinol, WBRKeyword::Purine ring, WBRKeyword::Alcohol, WBRKeyword::Pain, WBRKeyword::MSU, WBRKeyword::Monosodium urate, WBRKeyword::Allantoin, WBRKeyword::Urate, WBRKeyword::Uric acid, WBRKeyword::CRP |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |