Toxicology and Overdose Management — MCQs

Toxicology and Overdose Management Indian Medical PG Practice Questions and MCQs

Question 161: Which of the following is a long-term effect of chronic arsenic exposure?

A. Acute renal failure
B. Peripheral neuropathy (Correct Answer)
C. Acute respiratory distress
D. Severe gastrointestinal distress

Explanation: ***Peripheral neuropathy*** - **Chronic arsenic exposure** leads to damage of the peripheral nerves, causing **neurological symptoms** such as numbness, tingling, and weakness, particularly in the extremities [1]. - This typically manifests as a **stocking-glove distribution** neuropathy, indicating a long-term toxic effect. [1] *Acute renal failure* - **Acute renal failure** is more commonly associated with **acute arsenic poisoning** [3] or other specific nephrotoxic agents, rather than a chronic exposure. - While chronic exposure can cause kidney damage, it usually presents as **chronic kidney disease** over time, not an acute failure. *Acute respiratory distress* - **Acute respiratory distress** is typically seen in **acute toxic exposures** [2] or severe systemic illnesses, not a direct long-term effect of chronic arsenic exposure. - Chronic arsenic exposure is more linked to **lung cancer** and other respiratory complications that develop over years. *Severe gastrointestinal distress* - **Severe gastrointestinal distress** (e.g., vomiting, diarrhea, abdominal pain) is a prominent symptom of **acute arsenic poisoning** [4]. - While some mild GI symptoms may persist with chronic exposure, severe distress is not a characteristic long-term effect and usually points to an acute event.

Question 162: A patient presents with symptoms of snakebite, including pain, swelling, and coagulopathy. What is the first step in the management of snakebite envenomation?

A. Performing surgical excision
B. Applying a tourniquet
C. Administering anti-snake venom
D. Immobilizing the affected limb (Correct Answer)

Explanation: ***Immobilizing the affected limb*** - **Immobilizing** the limb helps to reduce the spread of **venom** through the lymphatic system and bloodstream by minimizing muscle movement [1], [2]. - This **first aid measure** can slow down venom absorption, providing more time for definitive medical treatment [1], [2]. *Administering anti-snake venom* - **Anti-snake venom (ASV)** is the definitive treatment for snakebite envenomation but it is usually administered after initial assessment and stabilization, and once clear signs of envenomation are evident [3]. - While critical, **ASV administration** is not typically the very first step upon presentation, as initial actions focus on preventing further venom spread and assessing the patient's condition. *Performing surgical excision* - **Surgical excision** of the bite site is generally **contraindicated** in snakebite management as it can worsen local tissue damage, increase bleeding, and potentially enhance venom absorption [1]. - This procedure carries significant risks and is not a recommended treatment for snakebite. *Applying a tourniquet* - The application of a **tourniquet** is **not recommended** for snakebites because it can cause severe tissue damage, including ischemia, nerve damage, and compartment syndrome [1]. - While it attempts to restrict venom spread, the risks associated with a tourniquet generally outweigh any potential benefits, and it can also lead to a dangerous sudden surge of venom once released [2].

Question 163: A 40-year-old female presents to the emergency department after ingesting an unknown quantity of acetaminophen. Laboratory results show elevated ALT and AST, increased PT, and decreased glucose. Analyze and determine the most appropriate treatment.

A. N-acetylcysteine (Correct Answer)
B. Activated charcoal
C. Liver transplant evaluation
D. Gastric lavage

Explanation: ***N-acetylcysteine*** - **N-acetylcysteine (NAC)** is the antidote for **acetaminophen overdose** and is critically important when there is evidence of liver damage (elevated ALT/AST, increased PT) and metabolic derangements (decreased glucose) [1]. - NAC works by replenishing **glutathione stores**, which helps detoxify the toxic metabolite **NAPQI**, preventing further hepatocellular damage [1]. *Activated charcoal* - **Activated charcoal** can be used for initial management of acetaminophen overdose, but only if administered within **1-2 hours** of ingestion to prevent absorption [2]. - Given the presence of **liver damage** (elevated ALT/AST, abnormal PT), it is likely that significant absorption has already occurred, making activated charcoal less effective now. *Liver transplant evaluation* - **Liver transplant evaluation** is indicated in cases of **fulminant hepatic failure** due to acetaminophen overdose that is unresponsive to NAC or where irreversible damage has occurred. - While the patient shows signs of liver injury, NAC is the **first-line treatment** aimed at reversing the damage and should be initiated promptly before considering transplantation. *Gastric lavage* - **Gastric lavage** is generally not recommended for acetaminophen overdose due to the **risk of complications** (e.g., aspiration) and **limited efficacy**, especially if not performed within 1 hour of ingestion. - Current guidelines prioritize oral activated charcoal within a narrow window, and NAC for established liver toxicity.

Question 164: What is the initial step in managing a patient with suspected carbon monoxide poisoning?

A. Administration of high-flow oxygen (Correct Answer)
B. Hyperbaric oxygen therapy
C. Oral hydration
D. Naloxone administration

Explanation: ***Administration of high-flow oxygen*** - The primary goal in carbon monoxide poisoning is to **displace CO from hemoglobin** [1] and improve tissue oxygenation [2], which is best achieved with high concentrations of inspired oxygen. - Using a **non-rebreather mask** at 10-15 L/min can significantly shorten the half-life of carboxyhemoglobin. *Hyperbaric oxygen therapy* - While beneficial for severe CO poisoning or in cases with neurological symptoms, **hyperbaric oxygen therapy** is not the initial step due to its limited availability and the need for immediate oxygen delivery at the scene or in the emergency department. - It's typically considered after initial stabilization with 100% oxygen and based on specific clinical criteria. *Oral hydration* - **Oral hydration** is supportive care and not the initial priority in a life-threatening situation like carbon monoxide poisoning, where immediate intervention to correct hypoxia is crucial. - Fluid management might be considered later, based on the patient's hydration status and overall clinical picture. *Naloxone administration* - **Naloxone** is an opioid antagonist used to reverse opioid overdose and has no role in the management of carbon monoxide poisoning. - Administering naloxone would delay appropriate treatment and provide no therapeutic benefit.

Question 165: Which metal poisoning is most commonly associated with nephropathy and may also cause muscle pain?

A. Cadmium (Correct Answer)
B. Lead
C. Arsenic
D. Mercury

Explanation: ***Cadmium*** - **Cadmium** exposure is strongly linked to **renal tubular dysfunction** and nephropathy, leading to impaired kidney function [1]. - While less common than kidney effects, cadmium toxicity can also manifest as **muscle pain** (myalgia) and bone pain due to its impact on calcium metabolism [1]. *Arsenic* - **Arsenic poisoning** primarily affects the skin (hyperkeratosis, hyperpigmentation), gastrointestinal tract (nausea, vomiting, diarrhea), and nervous system (neuropathy). - Although it can cause renal damage in severe acute cases, **nephropathy** is not its most common or defining feature compared to cadmium. *Lead* - **Lead poisoning** is well-known for causing **neurotoxicity** (encephalopathy in children, peripheral neuropathy in adults), **hematological abnormalities** (anemia), and **gastrointestinal symptoms** (colic). - While lead can cause chronic nephropathy (interstitial nephritis), it is not as predominantly associated with renal tubular damage and muscle pain in the same way as cadmium [2]. *Mercury* - **Mercury poisoning** typically presents with neurological symptoms (tremors, ataxia, behavioral changes from elemental mercury; paresthesias, visual disturbances from organic mercury). - **Kidney damage** (glomerular disease, nephrotic syndrome) can occur with inorganic mercury exposure, but it is not as consistently associated with tubular nephropathy and muscle pain as cadmium.

Question 166: Indications for liver transplant in PCM poisoning include all of the following except?

A. SGPT increase (Correct Answer)
B. PT > 100 seconds or INR > 6.5
C. High creatinine
D. Encephalopathy

Explanation: ***SGPT increase*** - An increase in **SGPT (ALT)** is an indicator of **liver damage**, but its absolute value alone is not a direct indication for **liver transplantation** in paracetamol (PCM) poisoning. More critical parameters are used for this decision. - While it signals liver injury, other factors like **coagulopathy** and **encephalopathy** are more directly linked to severe liver failure necessitating transplant consideration. *PT > 100 seconds or INR > 6.5* - A **prothrombin time (PT)** greater than 100 seconds or an **INR** greater than 6.5 indicates severe **coagulopathy**, a critical sign of **acute liver failure** and a strong indication for liver transplantation according to the **King's College Criteria**. - This reflects a profound impairment of the liver's synthetic function to produce **clotting factors**, leading to a high risk of bleeding. *High creatinine* - A **high creatinine level** indicates **renal impairment** or **acute kidney injury**, which is a common complication of severe **paracetamol poisoning** due to **hepatorenal syndrome** or direct toxicity. - Significant renal dysfunction, especially when coupled with other signs of severe liver failure, is a major component of the **King's College Criteria** for liver transplant. *Encephalopathy* - The presence of **encephalopathy** (any grade) in the setting of **acute liver failure** due to paracetamol poisoning is a crucial indicator for considering liver transplantation. - **Encephalopathy** signifies massive hepatocellular necrosis and the liver's inability to detoxify harmful substances, leading to neurological dysfunction.

Question 167: In a clinical context, the most common toxin causing Dilated Cardiomyopathy is:

A. Alcohol (Correct Answer)
B. Chemotherapeutic agents
C. Heavy metal
D. Occupational exposure

Explanation: ***Alcohol*** - Chronic excessive **alcohol consumption** is a well-established and prevalent cause of **dilated cardiomyopathy (DCM)**, leading to alcoholic cardiomyopathy [1]. - Alcohol and its metabolite, **acetaldehyde**, have direct toxic effects on **myocardial cells**, impairing contractility and leading to ventricular dilation [1]. *Chemotherapeutic agents* - Certain **chemotherapeutic agents**, such as **anthracyclines** (e.g., doxorubicin), can cause dose-dependent cardiotoxicity leading to DCM. - While significant, their incidence of causing DCM is less common in the general population compared to alcohol abuse. *Heavy metal* - **Heavy metal toxicity**, particularly from **lead**, **mercury**, or **cobalt**, can contribute to cardiomyopathy. - This is a less common cause of DCM in clinical practice compared to alcohol, often seen in specific industrial exposures or poisoning. *Occupational exposure* - **Occupational exposures** to certain chemicals or toxins can rarely cause DCM, but this category is broad and less frequently implicated than alcohol. - Specific toxins would need to be identified; without that, it's not the most common clinical cause.

Question 168: Pinpoint pupils are seen in all except?

A. Pontine hemorrhage
B. Opium poisoning
C. Organophosphorus poisoning
D. Barbiturate poisoning (Correct Answer)

Explanation: ***Barbiturate poisoning*** - While barbiturates can cause **central nervous system depression**, they typically lead to **dilated or normal pupils**, not constricted pupils. - The direct effect on the **autonomic nervous system** does not involve significant M2 receptor agonism to cause miosis. *Pontine hemorrhage* - A **pontine hemorrhage** directly damages the **sympathetic pathways** originating in the brainstem. - This interruption leads to unopposed **parasympathetic activity**, causing severe **miosis** or pinpoint pupils. *Organophosphorus poisoning* - Organophosphates inhibit **acetylcholinesterase**, leading to an accumulation of **acetylcholine** at muscarinic receptors (M2) in the eye [3]. - This excessive cholinergic stimulation results in profound **miosis**, also known as pinpoint pupils. *Opium poisoning* - Opium and other **opioids** activate **mu-opioid receptors** in the Edinger-Westphal nucleus, increasing parasympathetic outflow [1]. - This increased parasympathetic tone causes significant **miosis** or pinpoint pupils, a classic sign of opioid overdose [2].

Question 169: What type of neuropathy is most commonly associated with arsenic poisoning?

A. Symmetric peripheral sensory neuropathy (Correct Answer)
B. Asymmetrical peripheral motor neuropathy
C. Symmetrical peripheral motor neuropathy
D. Asymmetrical peripheral sensory neuropathy

Explanation: ***Symmetric peripheral sensory neuropathy*** - Arsenic poisoning commonly causes a **symmetric peripheral neuropathy**, primarily affecting **sensory nerves** [1]. - Patients often experience a **stocking-glove distribution** of paresthesias, numbness, and pain due to damage to longer nerve fibers [1]. *Asymmetrical peripheral motor neuropathy* - This type of neuropathy is **less characteristic** of arsenic poisoning, which predominantly affects sensory fibers symmetrically. - **Motor deficits** can occur but are typically secondary to sensory loss and not primarily asymmetric. *Symmetrical peripheral motor neuropathy* - While arsenic can affect motor nerves, it's typically a **secondary effect** and not the primary presentation. - The most prominent and initial neuropathy in arsenic poisoning is **sensory**, not purely motor. *Asymmetrical peripheral sensory neuropathy* - The sensory neuropathy in arsenic poisoning is characteristically **symmetrical**, affecting both sides of the body equally. - Asymmetrical presentation is **uncommon** for arsenic-induced neuropathy.

Question 170: A patient on anti-depressants presented to you with hypotension. An ECG was done, which showed wide QRS complexes and right axis deviation. How will you manage this patient?

A. Intravenous sodium bicarbonate for TCA-induced arrhythmias (Correct Answer)
B. Use of antiarrhythmics
C. Administration of propranolol
D. Use of phenytoin

Explanation: Intravenous sodium bicarbonate for TCA-induced arrhythmias - The patient's presentation with **hypotension**, **wide QRS complexes**, and **right axis deviation** in the context of antidepressant use is highly suggestive of **Tricyclic Antidepressant (TCA) toxicity**. [1] - **Sodium bicarbonate** improves cardiac function by increasing plasma sodium and alkalizing the blood, which reduces the binding of TCAs to myocardial fast sodium channels and alleviates cardiotoxicity. [1] *Use of antiarrhythmics* - Many antiarrhythmics, particularly **Class IA and IC agents**, block sodium channels and could exacerbate TCA-induced cardiotoxicity. [1] - Furthermore, antiarrhythmics may worsen hypotension and prolong the QRS interval in TCA overdose. *Administration of propranolol* - **Propranolol** is a non-selective beta-blocker that can worsen **hypotension** and **bradycardia**, which are common in TCA overdose. - It would not address the primary issue of **sodium channel blockade** caused by TCAs. *Use of phenytoin* - **Phenytoin** acts by blocking sodium channels and is used for certain arrhythmias, but its efficacy in TCA toxicity is limited and can be proarrhythmic. - **Sodium bicarbonate** is the preferred treatment as it is more effective at reversing the cardiotoxic effects of TCAs. [1]

Practice by Chapter

General Principles of Toxicology

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Antidotes and Specific Therapies

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Drug Overdose Management

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Heavy Metal Poisoning

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Pesticide and Insecticide Poisoning

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Plant and Food Toxins

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Household Chemical Exposure

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Environmental Toxins

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Occupational Exposures

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Toxicological Screening and Diagnosis

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Extracorporeal Removal Techniques

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Poisoning Prevention Strategies

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