A 17-year-old girl with a history of depression is brought to the emergency department after attempting suicide. Her parents report that she consumed 2 bottles of insecticide after having an argument with her sister approximately 2 hours prior to presentation. The patient’s symptoms include nausea, vomiting, abdominal pain, and copious watery diarrhea. She has a known history of self-cutting and suicidal ideations but no prior suicide attempts. Blood pressure is 86/42 mm Hg and pulse is 120/min. Her breath has a faint garlic odor, and she has numerous healing linear scars on her forearms. Which of the following medications should be administered immediately?
Arsenic poisoning | |
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Arsenic is odorless, tasteless, and easily absorbed after ingestion or inhalation. Toxicity can result from exposure to pesticides/insecticides, contaminated water, pressure-treated wood, metallurgy, mining, or glass-making. Arsenic binds to sulfhydryl groups, impairing cellular respiration via inhibition of pyruvate dehydrogenase and disruption of gluconeogenesis and glutathione metabolism.
Acute arsenic poisoning affects most organ systems and presents with abdominal pain, vomiting, severe watery diarrhea, delirium, and hypotension from dehydration. QTc prolongation can progress to life-threatening torsades de pointes. A garlic odor is often noted on the patient's breath or stool.
The first-line chelating agent is dimercaprol (eg, British Anti-Lewisite), which increases urinary excretion of heavy metals by forming stable, nontoxic soluble chelates. The sulfhydryl group of dimercaprol combines with arsenic and displaces arsenic ions from the sulfhydryl groups of enzymes involved in cellular respiration. Dimercaprol has a very narrow therapeutic index, and serious side effects include nephrotoxicity, hypertension, and fever.
(Choice A) Acute lead poisoning can present with constipation, anemia, and irritability and confusion. CaNa2EDTA is a treatment option for lead toxicity and works by forming non-ionizing salts to increase urinary lead excretion.
(Choice B) Deferoxamine is the preferred chelating agent for iron overdoses or overload due to multiple blood transfusions. It binds circulating iron and facilitates its urinary excretion.
(Choice D) Cyanide poisoning presents with confusion, flushing or a "cherry-red" skin color, abdominal pain, and vomiting. Its antidote, hydroxycobalamin (vitamin B12 precursor), binds to intracellular cyanide forming cyanocobalamin, which can be easily excreted in urine.
(Choice E) Methylene blue is indicated for treatment of methemoglobinemia, which presents with gray- or blue-colored skin, shortness of breath, and "chocolate-colored" blood. Methylene blue acts as an artificial electron transporter for reduction of methemoglobin through the NADPH pathway.
Educational objective:
Acute arsenic poisoning impairs cellular respiration and presents with abdominal pain, vomiting, diarrhea, hypotension, and a garlic odor on the breath. Insecticides and contaminated water are common sources of arsenic. Dimercaprol is the chelating agent of choice.