{"id":497,"date":"2023-01-04T01:22:00","date_gmt":"2023-01-04T01:22:00","guid":{"rendered":"https:\/\/www.osmosis.org\/blog\/?p=497"},"modified":"2025-10-01T11:40:35","modified_gmt":"2025-10-01T19:40:35","slug":"usmle-step-1-question-of-the-day-anticholinesterase-poisoning","status":"publish","type":"post","link":"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning","title":{"rendered":"USMLE\u00ae Step 1 Question of the Day: Anticholinesterase poisoning"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_80 ez-toc-wrap-center counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">In This Article<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#The_correct_answer_to_todays_USMLE%C2%AE_Step_1_Question_is%E2%80%A6\" >The correct answer to today&#8217;s USMLE\u00ae Step 1 Question is&#8230;<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#B_Organophosphate\" >B.&nbsp;Organophosphate<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#Incorrect_answer_explanations\" >Incorrect answer explanations<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#A_Atropine\" >A. Atropine<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#C_Amitriptyline\" >C. Amitriptyline<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#D_Caustic_substances\" >D. Caustic substances<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#E_Amphetamine\" >E. Amphetamine<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#Main_Explanation\" >Main Explanation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#Major_Takeaway\" >Major Takeaway<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\/#References\" >References<\/a><\/li><\/ul><\/nav><\/div>\n\n<p class=\"wp-block-paragraph\"><strong><em>This week, we are sharing another USMLE\u00ae Step 1-style practice question to test your knowledge of medical topics.&nbsp;<\/em><\/strong><strong><em>Today&#8217;s case focuses on a 35-year-old-woman who has difficulty breathing. Physical examination reveals a lethargic and diaphoretic adult female with bilateral pinpoint pupils and watering from the eyes.&nbsp;<strong><em>Can you figure it out?<\/em><\/strong><\/em><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 35-year-old woman is brought to the emergency department due to difficulty breathing. The patient is a farmer and developed symptoms while working in the fields. Past medical history is significant for major depressive disorder and two prior suicide attempts. Temperature is 36.7\u00b0C (98.1\u00b0F), pulse is 53\/min, respirations are 32\/min, and blood pressure is 90\/65 mmHg. Oxygen saturation is 87% on ambient air. Physical examination reveals a lethargic and diaphoretic adult female with bilateral pinpoint pupils and watering from the eyes. The patient\u2019s body and clothes are soiled in vomit and feces. Lung auscultation reveals diffuse wheezing with rhonchi. Which of the following agents most likely precipitated this patient&#8217;s symptoms?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>A. Atropine<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>B. Organophosphate<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>C. Amitriptyline<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>D. Caustic substances<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>E. Amphetamine<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"The_correct_answer_to_todays_USMLE%C2%AE_Step_1_Question_is%E2%80%A6\"><\/span>The correct answer to today&#8217;s USMLE\u00ae Step 1 Question is&#8230;<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"B_Organophosphate\"><\/span>B.&nbsp;<strong>Organophosphate<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Before we get to the Main Explanation, let&#8217;s look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Incorrect_answer_explanations\"><\/span>Incorrect answer explanations<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The incorrect answers to today&#8217;s USMLE\u00ae Step 1 Question are&#8230;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"A_Atropine\"><\/span>A. Atropine<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:&nbsp;<\/strong>Atropine is a muscarinic antagonist. Atropine toxicity can present with mydriasis (dilated pupils), increased body temperature, constipation, and dry flushed skin. This patient\u2019s presentation is inconsistent with the symptoms of atropine toxicity and instead more suggestive of organophosphate toxicity.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"C_Amitriptyline\"><\/span>C. Amitriptyline<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:&nbsp;<\/strong>Amitriptyline is a tricyclic antidepressant with anticholinergic properties. Tricyclic antidepressant toxicity can present with mydriasis, increased body temperature, dry mouth, tachycardia, and flushed skin. This patient\u2019s presentation is inconsistent with the symptoms of amitriptyline toxicity.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"D_Caustic_substances\"><\/span>D. Caustic substances<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:&nbsp;<\/strong>Ingestion of caustic substances (e.g., bleach, drain cleaners) can cause stridor, hoarseness, dysphagia, and oropharyngeal ulceration. In contrast to this patient\u2019s presentation, it would not typically cause pinpoint pupils, bradycardia, or diaphoresis.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"E_Amphetamine\"><\/span>E. Amphetamine<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Incorrect:<\/strong>&nbsp;Amphetamine is a sympathomimetic agent. Although amphetamine overdose can present with tachypnea and increased sweating, the pupils are typically dilated, and blood pressure is elevated.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Main_Explanation\"><\/span>Main Explanation<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This patient presents with&nbsp;<strong>dyspnea, bradycardia, miosis, and excessive secretions (e.g., diaphoresis, lacrimation).<\/strong>&nbsp;These symptoms are highly suggestive of&nbsp;<strong>organophosphate poisoning.&nbsp;<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Organophosphates can be found in insecticides, herbicides, and nerve agents. Agricultural workers are at increased risk for organophosphate poisoning. The substance binds to acetylcholinesterase (AChE), which is normally responsible for the hydrolysis of acetylcholine and renders the enzyme non-functional. With AChE blocked, acetylcholine subsequently accumulates and leads to hyperstimulation of nicotinic and muscarinic receptors. Nicotinic stimulation leads to neuromuscular blockade, and muscarinic activation results in increased visceral and glandular secretions. Organophosphates may also contribute to central respiratory depression, lethargy, and ultimately coma. A brief overview of the clinical features of organophosphate toxicity is found in the table below.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">P.S. If you or someone you know needs this, here&#8217;s the number for the National Suicide Prevention Lifeline 1-800-273-8255 or text HOME to the Crisis Text Line at 741741.&nbsp;<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" height=\"655\" width=\"1024\" src=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/08\/75.png?w=1024\" alt=\"table of organophosphate poisoning and their different effects in the body and how to manage them.\" class=\"wp-image-499\" srcset=\"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/08\/75.png 1304w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/08\/75.png?resize=300,192 300w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/08\/75.png?resize=768,491 768w, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/08\/75.png?resize=1024,655 1024w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Major_Takeaway\"><\/span>Major Takeaway<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Organophosphate poisoning<\/strong>&nbsp;can lead to symptoms of&nbsp;<strong>nicotinic hyperstimulation<\/strong>&nbsp;(neuromuscular blockade),&nbsp;<strong>muscarinic hyperstimulation&nbsp;<\/strong>(increased visceral and glandular secretions), as well as&nbsp;<strong>central nervous system symptoms<\/strong>. Organophosphates are found in insecticides and herbicides. As a result, agricultural workers are at increased risk of organophosphate poisoning.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"References\"><\/span>References<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Eddleston, M., Buckley, N.A., Eyer, P., Dawson, A.H. (2008) Management of acute organophosphorus pesticide poisoning.&nbsp;<em>The Lancet<\/em>. 371(9612), 597-607. Doi: 10.1016\/S0140-6736(07)61202-1.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Eddleston, M., Phillips, M.R. (2004) Self-poisoning with pesticides.&nbsp;<em>BMJ<\/em>. 328(7430), 42-44. Doi: 10.1136\/bmj.328.7430.42.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Khurana, D., Prabhakar, S. (2000) Organophosphorus intoxication.&nbsp;<em>Archives of Neurology<\/em>. 57(4), 600-602. Doi: 10.1001\/archneur.57.4.600.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">King, A.M., Aaron, C.K. (2015) Organophosphate and carbamate poisoning.&nbsp;<em>Emergency Medicine Clinics of North America<\/em>. 33(1), 133-151. Doi: 10.1016\/j.emc.2014.09.010.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>This week, we are sharing another USMLE\u00ae Step 1-style practice question to test your knowledge of medical topics.&nbsp;Today&#8217;s case focuses on a 35-year-old-woman who has difficulty breathing. Physical examination reveals a lethargic and diaphoretic adult female with bilateral pinpoint pupils and watering from the eyes.&nbsp;Can you figure it out? A 35-year-old woman is brought to [&hellip;]<\/p>\n","protected":false},"author":202,"featured_media":498,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[27,20,1369,44],"tags":[],"class_list":["post-497","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicine","category-exam-prep","category-step-1-questions","category-step-1"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>USMLE\u00ae Step 1 Question of the Day: Anticholinesterase poisoning - Osmosis Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-anticholinesterase-poisoning\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"USMLE\u00ae Step 1 Question of the Day: Anticholinesterase poisoning - Osmosis Blog\" \/>\n<meta property=\"og:description\" content=\"This week, we are sharing another USMLE\u00ae Step 1-style practice question to test your knowledge of medical topics.&nbsp;Today&#8217;s case focuses on a 35-year-old-woman who has difficulty breathing. Physical examination reveals a lethargic and diaphoretic adult female with bilateral pinpoint pupils and watering from the eyes.&nbsp;Can you figure it out? 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Which of\u2026","rel":"","context":"In &quot;Allopathic Medicine (MD)&quot;","block_context":{"text":"Allopathic Medicine (MD)","link":"https:\/\/www.osmosis.org\/blog\/category\/medicine"},"img":{"alt_text":"USMLE\u00ae Step 1 Question of the Day: Gonorrhea","src":"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/95.webp","width":350,"height":200,"srcset":"https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/95.webp 1x, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/95.webp 1.5x, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/95.webp 2x, https:\/\/www.osmosis.org\/blog\/wp-content\/uploads\/sites\/2\/2024\/09\/95.webp 3x"},"classes":[]},{"id":614,"url":"https:\/\/www.osmosis.org\/blog\/usmle-step-1-question-of-the-day-hairy-leukoplakia","url_meta":{"origin":497,"position":5},"title":"USMLE\u00ae Step 1 Question of the Day: Hairy leukoplakia","author":"Marina Horiates Kerekes, MD &amp; Team","date":"March 8, 2023","format":false,"excerpt":"This week, we are sharing another USMLE\u00ae Step 1-style practice question to test your knowledge of medical topics.\u00a0Today's case focuses on a 51-year-old woman who comes to the clinic for an assessment of a tongue lesion. 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