WBR0478
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology, MainCategory::Pharmacology |
| Sub Category | SubCategory::Dermatology |
| Prompt | [[Prompt::A 42 year old female patient presents to the dermatology clinic with a complaint of nail lesion. Following appropriate work-up, the diagnosis of onychomycosis is made. She was prescribed an antimicrobial medication that was then stopped due to alteration of liver function tests. What is the mechanism of action that best describes the medication prescribed for this patient?]] |
| Answer A | AnswerA::Inhibits squalene epoxidase |
| Answer A Explanation | AnswerAExp::Terbinafine is a squalene epoxidase inhibitor. It is the first line treatment for onychomycosis. Liver function tests must be monitored due to terbinafine's hepatic adverse reaction. |
| Answer B | AnswerB::Inhibits DNA polymerase |
| Answer B Explanation | AnswerBExp::Several antiviral medications inhibit DNA polymerase. They are not used to treat onychomycosis. |
| Answer C | AnswerC::Inhibits aminoacyl-tRNA attachment |
| Answer C Explanation | AnswerCExp::Tetracyclines inhibit aminoacyl-tRNA attachment. They are not used to treat onychomycosis. |
| Answer D | AnswerD::Inhibits synthesis of beta-glucan |
| Answer D Explanation | AnswerDExp::Caspofungin inhibits synthesis of beta-glucan. It is not used to treat onychomycosis. |
| Answer E | AnswerE::Inhibits ergosterol synthesis |
| Answer E Explanation | AnswerEExp::Azoles inhibit ergosterol synthesis. They are not used to treat onychomycosis. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Terbinafine is considered first line treatment for onychomycosis. Terbinafine is an antifungal that inhibits squalene epoxidase. Its most common side effects are altered liver function tests (LFTs) and visual disturbance. Patients are usually requested to routinely perform LFT testing during treatment with terbinafine to monitor to drug-induced liver injury (DILI).
Educational Objective:
Terbinafine is first line treatment for onychomycosis. It is an antifungal that inhibits squalene epoxidase. Liver injury is a potential side effect of terbinafine. |
| Approved | Approved::No |
| Keyword | WBRKeyword::terbinafine, WBRKeyword::drug, WBRKeyword::induced, WBRKeyword::liver, WBRKeyword::injury, WBRKeyword::DILI, WBRKeyword::adverse, WBRKeyword::reaction, WBRKeyword::side, WBRKeyword::effect, WBRKeyword::adverse drug reaction, WBRKeyword::side effect, WBRKeyword::antifungal, WBRKeyword::onychomycosis, WBRKeyword::liver, WBRKeyword::function, WBRKeyword::test, WBRKeyword::LFT, WBRKeyword::liver functon test |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |