WBR0349
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathophysiology, MainCategory::Pharmacology |
| Sub Category | SubCategory::Hematology |
| Prompt | [[Prompt::A 23 year old woman is brought to the emergency department after consuming rat poison in a suicide attempt. On arrival, EMS report several episode of hematemesis on the way to the hospital. The patient is found to be hypotensive and tachycardic with altered mental status. Which of the following mechanisms are responsible for this patient's presentation?]] |
| Answer A | AnswerA::Inhibition of epoxide reductase |
| Answer A Explanation | AnswerAExp::Rodenticides are usually derivatives of coumarin and inhibit epoxide reductase leading to a decrease in clotting factors. |
| Answer B | AnswerB::Activation of plasminogen |
| Answer B Explanation | AnswerBExp::Fibrinolytics typically cause activation of plasminogen. Rat poison works by a different mechanism. |
| Answer C | AnswerC::Activation of antithrombin III |
| Answer C Explanation | AnswerCExp::Heparin causes activation of antithrombin III. Rat poison works by a different mechanism. |
| Answer D | AnswerD::Inhibition of GpIIbIIIa expression |
| Answer D Explanation | AnswerDExp::ADP receptor blockers such as clopidogrel cause inhibition of GpIIbIIIa expression. Rat poison works by a different mechanism. |
| Answer E | AnswerE::Inhibition of thromboxane A2 production |
| Answer E Explanation | AnswerEExp::Aspirin inhibits thromboxane A2 production leading to a decrease in platelet aggregation. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Rodenticides, or rat poisons are a variety of agent used to exterminate rodents. The most commonly used rodenticides are anticoagulants typically of the coumarin class notably warfarin, coumatetralyl, difenacoum, and brodifacoum. They are also known as superwarfarins due to their substituted phenyl groups replacing the terminal methyl groups, that make these agents approximately 100 times more potent than regular coumarins. These agents act as they would for therapeutic purposes by inhibiting the gamma-carboxylation of coagulation factors that requires vitamin K. Coumarins inhibit the enzyme epoxide reductase that forms the active vitamin K needed for carboxylation. Blood levels of factors II, VII, IX and X drop to dangerously low levels after ingestion of large doses of rat poison usually leading to massive GI bleeding that may manifest as hematemesis. Treatment for early ingestion includes syrup of ipecac and gastric lavage. For late cases presenting with massive bleeding, treatment is typically with fresh frozen plasma and vitamin K administration.
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| Approved | Approved::No |
| Keyword | WBRKeyword::Rat poison, WBRKeyword::Vitamin K, WBRKeyword::Fresh frozen plasma, WBRKeyword::epoxide reductase |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |