WBR0529
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| Author | [[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::To study the effects of a newly developed drug, a researcher uses polarized microscopy to monitor the changes in living Pectinaria oocytes exposed to intermittent doses of this agent. Although most oocytes are not directly affected, those in active replication seem to arrest at a certain point during mitosis with a significant reduction in the size of meiotic spindles, as measured by loss of birefringence under polarized light. The researcher also notices that shortly after the drug is washed, mitosis would resume and the spindles would regain birefringence. Which of the following drugs most likely has the same mechanism of action?]] |
| Answer A | AnswerA::Carboplatin |
| Answer A Explanation | AnswerAExp::Carboplatin is a chemotherapeutic agent that cross-links DNA. |
| Answer B | AnswerB::Amantadine |
| Answer B Explanation | AnswerBExp::Amantadine is an antiviral drug that inhibits influenza uncoating by binding to the M2 protein. |
| Answer C | AnswerC::Griseofulvin |
| Answer C Explanation | AnswerCExp::Griseofulvin is a fungistatic agent that inhibits microtubule polymerization and inhibits mitosis. |
| Answer D | AnswerD::Etoposide |
| Answer D Explanation | AnswerDExp::Etoposide is an antineoplastic agent that acts as a topoisomerase inhibitor. |
| Answer E | AnswerE::Caspofungin |
| Answer E Explanation | AnswerEExp::Caspofungin is an antifungal drug that inhibits the enzyme β-glucan synthase and disturbs the integrity of the fungal cell wall. |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::Griseofulvin is a fungistatic antifungal drug used mostly in the treatment of fungal skin infections. It is deposited in keratin precursor cells and tightly bound to keratin, which explains its efficacy in dermatologic infections. It acts by inhibiting mitosis strongly in fungal cells and weakly in mammalian cells by affecting mitotic spindle microtubule function. It binds to microtubules and inhibits their ability to polymerize leading a decrease in the effective mitotic spindles. It is among the fastest reversible drugs acting on microtubules. Common side effects include urticaria and drug induced rashes. A more severe but rare adverse effect is severe liver toxicity. Treatment is indicated for resistant infections affecting skin, body, hair, or nails, including tinea capitis, tinea corporis, and tinea pedis. Educational Objective: Griseofulvin is a fungistatic agent that inhibits microtubule polymerization halting mitotic divison. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Griseofulvin, WBRKeyword::Microtubule, WBRKeyword::Mitosis, WBRKeyword::Antifungal, WBRKeyword::Fungistatic, WBRKeyword::Fungal infection |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |