Toxicology and Overdose Management — MCQs
On this page
What is the treatment of choice for a patient with chronic alcoholism presenting with altered sensorium, normal random blood sugar, and normal blood urea nitrogen?
A 40-year-old man presents with altered mental status after ingesting an unknown medication. His vital signs are: temperature 103°F, BP 120/85 mmHg, pulse 100/min, and respiratory rate 22/min. Physical examination reveals flushed and dry skin, dilated pupils, and muscle twitching. ECG shows prolonged QRS complexes. Laboratory results are notable for normal hepatic transaminases and a normal arterial blood gas pH. These clinical and laboratory findings are most likely indicative of intoxication by which of the following substances?
Paraquat poisoning causes which of the following?
A patient presents with sudden respiratory distress. On examination, bilateral miosis and bilateral basal crepitations suggestive of pulmonary edema with normal alveolar wedge pressure are present. What is the likely cause?
What is the most important step in managing aspirin poisoning?
Which of the following is most likely in a 23-year-old female who died due to overdose of acetaminophen?
A 39-year-old carpenter develops confusion, vomiting, and blurring of vision about an hour after consuming two bottles of liquor. He has been brought to the emergency department. What should be administered?
Which of the following is NOT a recommended treatment for snakebite?
Gastric lavage is contraindicated in which of the following poisoning scenarios? 1. Kerosene poisoning 2. Organo-phosphorus poisoning 3. Corrosive poisoning 4. Iron poisoning
What is the mechanism of action of ethyl alcohol in methyl alcohol poisoning?
Toxicology and Overdose Management Indian Medical PG Practice Questions and MCQs
Question 81: What is the treatment of choice for a patient with chronic alcoholism presenting with altered sensorium, normal random blood sugar, and normal blood urea nitrogen?
- A. Vitamin B1 injection IM (Correct Answer)
- B. Dextrose 50%
- C. Dextrose 10%
- D. Normal saline
Explanation: The clinical presentation of a patient with chronic alcoholism and altered sensorium, despite normal blood sugar levels, strongly suggests **Wernicke’s Encephalopathy (WE)** [1]. This is a medical emergency caused by a deficiency of **Vitamin B1 (Thiamine)** [1]. **1. Why Vitamin B1 (Thiamine) is the Correct Choice:** Thiamine is a critical cofactor for glucose metabolism (specifically for enzymes like pyruvate dehydrogenase) [4]. In chronic alcoholics, thiamine stores are depleted due to poor intake and impaired absorption [1]. Even if blood sugar is normal, the brain cannot utilize glucose effectively without thiamine, leading to encephalopathy. Immediate parenteral administration (IM or IV) is mandatory to prevent permanent neurological damage or progression to **Korsakoff Syndrome** [2]. **2. Why Other Options are Incorrect:** * **Dextrose 50% & 10% (B & C):** These are used for hypoglycemia. Since the patient has a **normal random blood sugar**, dextrose is not indicated. Crucially, giving dextrose *before* thiamine in a thiamine-deficient patient can precipitate or worsen Wernicke’s Encephalopathy by acutely consuming the remaining thiamine stores during glycolysis [2]. * **Normal Saline (D):** While useful for volume resuscitation, it does not address the underlying metabolic cause of altered sensorium in this specific clinical context. **3. NEET-PG High-Yield Pearls:** * **Classic Triad of WE:** Confusion (Altered sensorium), Ataxia, and Ophthalmoplegia (usually 6th nerve palsy/nystagmus) [3]. * **Rule of Thumb:** In any alcoholic or malnourished patient with altered mental status, **always give Thiamine before Dextrose** [2]. * **Diagnosis:** Primarily clinical. MRI may show high signal intensity in the **mammillary bodies** (most characteristic finding) [4]. * **Korsakoff Syndrome:** Characterized by anterograde amnesia and **confabulation** [3].
Question 82: A 40-year-old man presents with altered mental status after ingesting an unknown medication. His vital signs are: temperature 103°F, BP 120/85 mmHg, pulse 100/min, and respiratory rate 22/min. Physical examination reveals flushed and dry skin, dilated pupils, and muscle twitching. ECG shows prolonged QRS complexes. Laboratory results are notable for normal hepatic transaminases and a normal arterial blood gas pH. These clinical and laboratory findings are most likely indicative of intoxication by which of the following substances?
- A. Acetaminophen
- B. Alcohol
- C. Benzodiazepines
- D. Tricyclic antidepressants (Correct Answer)
Explanation: The clinical presentation described is a classic toxidrome of **Tricyclic Antidepressant (TCA) overdose** [1]. TCAs have a complex pharmacological profile that leads to three primary categories of symptoms: 1. **Anticholinergic Effects:** The "dry and flushed skin," hyperthermia (103°F), and dilated pupils (mydriasis) are hallmark signs of muscarinic receptor blockade. 2. **Cardiovascular Toxicity:** The **prolonged QRS complex** is the most specific finding, caused by the inhibition of fast sodium channels in the myocardium [2]. This slowing of depolarization increases the risk of ventricular arrhythmias and seizures [2]. 3. **CNS Effects:** Altered mental status and muscle twitching (myoclonus) occur due to antihistaminic and anticholinergic actions. **Why other options are incorrect:** * **Acetaminophen:** Toxicity typically presents with nausea, vomiting, and later, signs of hepatic failure (elevated transaminases). It does not cause anticholinergic symptoms or QRS widening. * **Alcohol:** Acute intoxication usually presents with CNS depression, slurred speech, and ataxia. While it can cause altered mental status, it does not cause the "dry/flushed" anticholinergic syndrome. * **Benzodiazepines:** These cause CNS depression with relatively stable vital signs ("coma with normal vitals") [1]. They do not cause hyperthermia, mydriasis, or ECG changes. **High-Yield Clinical Pearls for NEET-PG:** * **ECG Marker:** A QRS duration **>100 ms** is a predictor of seizures; **>160 ms** is a predictor of ventricular arrhythmias [2]. * **Antidote:** The first-line treatment for QRS widening or arrhythmias in TCA overdose is **Sodium Bicarbonate (NaHCO₃)** [2]. It works by increasing extracellular sodium and alkalinizing the blood to decrease drug binding to sodium channels [2]. * **Avoid:** Class IA and IC antiarrhythmics are contraindicated as they further worsen sodium channel blockade.
Question 83: Paraquat poisoning causes which of the following?
- A. Renal failure
- B. Cardiac failure
- C. Respiratory failure
- D. Multiple organ failure (Correct Answer)
Explanation: **Explanation:** Paraquat is a highly toxic bipyridylium herbicide. Its toxicity is primarily mediated by **redox cycling**, where it undergoes cyclic reduction and re-oxidation, generating massive amounts of **Reactive Oxygen Species (ROS)** like superoxide radicals [1]. This leads to widespread lipid peroxidation and cell membrane destruction across multiple organ systems. **Why Multiple Organ Failure (MOF) is the correct answer:** While Paraquat is notorious for its effects on the lungs, it is a systemic toxin. Following ingestion, it is distributed via the bloodstream to various organs. High concentrations accumulate in the lungs and kidneys via the polyamine transport system [1]. Acute poisoning typically manifests as a **multisystem involvement** including: * **GI:** Corrosive injury to the mouth and esophagus. * **Renal:** Acute Tubular Necrosis (ATN) and renal failure. * **Hepatic:** Centrilobular necrosis and jaundice. * **Pulmonary:** Pulmonary edema followed by irreversible **Pulmonary Fibrosis** [2]. **Why other options are incorrect:** * **Renal and Cardiac Failure:** While these occur, they are components of the broader systemic collapse. Selecting only one ignores the hallmark "multi-organ" nature of the toxin [1]. * **Respiratory Failure:** This is the most common cause of *late* death (due to fibrosis), but in the acute phase, the patient suffers from a combination of circulatory, renal, and respiratory collapse. **High-Yield Clinical Pearls for NEET-PG:** 1. **The Paraquat Paradox:** Oxygen therapy is generally **contraindicated** (unless $PaO_2 < 40$ mmHg) because supplemental oxygen provides more substrate for ROS generation, actually accelerating lung injury and fibrosis. 2. **Diagnosis:** Confirmed by the **Sodium Dithionite Urine Test** (turns blue/green in the presence of Paraquat). 3. **Management:** Focuses on aggressive decontamination (Fuller’s Earth or Activated Charcoal) and immunosuppression (Cyclophosphamide/Steroids), though the prognosis remains poor.
Question 84: A patient presents with sudden respiratory distress. On examination, bilateral miosis and bilateral basal crepitations suggestive of pulmonary edema with normal alveolar wedge pressure are present. What is the likely cause?
- A. Narcotic overdose (Correct Answer)
- B. Congestive heart failure
- C. Myocardial infarction
- D. Cardiogenic shock
Explanation: **Explanation:** The clinical presentation of **bilateral miosis (pinpoint pupils)** combined with **non-cardiogenic pulmonary edema (NCPE)** is a classic triad for **Narcotic (Opioid) overdose** [1]. **1. Why Narcotic Overdose is Correct:** Opioids (especially Heroin and Morphine) cause a triad of symptoms: CNS depression, respiratory depression, and miosis [1]. A well-known but critical complication of opioid toxicity is **Non-Cardiogenic Pulmonary Edema** [1]. The underlying mechanism involves increased capillary permeability and negative pressure ventilation against a closed glottis. The presence of **normal pulmonary capillary wedge pressure (PCWP)** is the diagnostic hallmark that distinguishes NCPE from heart failure, as it indicates that the edema is not due to fluid backup from a failing left ventricle. **2. Why Incorrect Options are Wrong:** * **Congestive Heart Failure (CHF), Myocardial Infarction (MI), and Cardiogenic Shock:** All three conditions cause **Cardiogenic Pulmonary Edema**. In these cases, the PCWP would be **elevated** (>18 mmHg) due to left ventricular dysfunction. Furthermore, these conditions typically present with tachycardia or chest pain rather than miosis (unless the patient is on specific medications like clonidine). **Clinical Pearls for NEET-PG:** * **Miosis + Respiratory Depression + Coma** = Opioid Overdose [1], [2]. * **Exception to Miosis:** Meperidine (Pethidine) overdose often presents with **mydriasis** (dilated pupils) due to its atropine-like effects. * **Management:** The definitive treatment is **Naloxone** (opioid antagonist) [3]. * **High-Yield NCPE Causes:** Opioids, Salicylates, High Altitude (HAPE), and Neurogenic causes.
Question 85: What is the most important step in managing aspirin poisoning?
- A. Fluid administration (Correct Answer)
- B. Alkalinization of urine
- C. External warming
- D. Blood transfusion
Explanation: In aspirin (salicylate) poisoning, the primary goal is to address the metabolic derangements and enhance elimination. [2] **Why Fluid Administration is the Correct Answer:** The most critical initial step is **aggressive fluid resuscitation**. Salicylate toxicity causes a high anion gap metabolic acidosis, hyperthermia, and increased insensible water loss (due to tachypnea and diaphoresis). [2] Dehydration significantly impairs the kidneys' ability to excrete salicylates. [3] Restoring intravascular volume and ensuring adequate urine output (2–3 mL/kg/hr) is a prerequisite for any further treatment, including urinary alkalinization. Without adequate hydration, the kidneys cannot effectively respond to bicarbonate therapy. **Why Other Options are Incorrect:** * **Alkalinization of urine:** While this is a definitive treatment to enhance salicylate excretion (ion trapping), it cannot be effectively achieved in a dehydrated patient. [4] Correction of hypovolemia and hypokalemia must occur first. * **External warming:** This is contraindicated. Aspirin uncouples oxidative phosphorylation, leading to hyperthermia. [2] Patients often require **external cooling**, not warming. * **Blood transfusion:** There is no role for routine blood transfusion in aspirin toxicity unless there is significant gastrointestinal bleeding, which is not the primary concern in acute overdose. **NEET-PG High-Yield Pearls:** * **Acid-Base Pattern:** The classic "mixed" pattern is **Respiratory Alkalosis** (due to direct stimulation of the medullary respiratory center) + **Metabolic Acidosis** (due to uncoupling of oxidative phosphorylation). [2] * **Ion Trapping:** Alkalinizing the urine (pH 7.5–8.5) converts salicylic acid to its ionized form (salicylate), preventing reabsorption in the renal tubules. [4] * **Hemodialysis Indications:** Serum levels >100 mg/dL (acute) or >60 mg/dL (chronic), altered mental status, or refractory acidosis. [1]
Question 86: Which of the following is most likely in a 23-year-old female who died due to overdose of acetaminophen?
- A. Cirrhosis of the liver
- B. Hepatorenal syndrome
- C. Acute liver failure (Correct Answer)
- D. Sinusoidal obstruction syndrome
Explanation: **Explanation:** **Correct Answer: C. Acute Liver Failure** Acetaminophen (Paracetamol) overdose is the leading cause of drug-induced **Acute Liver Failure (ALF)** worldwide. The toxicity is mediated by the metabolite **NAPQI** (N-acetyl-p-benzoquinone imine) [2]. At therapeutic doses, NAPQI is detoxified by glutathione. In overdose, glutathione stores are exhausted, leading to NAPQI-induced oxidative stress and **centrilobular (Zone 3) hepatic necrosis** [1], [2]. This manifests clinically as rapid-onset encephalopathy and coagulopathy (INR >1.5) within days of ingestion, defining ALF [3]. **Analysis of Incorrect Options:** * **A. Cirrhosis of the liver:** This is a chronic process resulting from long-term inflammation and fibrosis (e.g., Alcohol, Hepatitis B/C). Acetaminophen causes acute, massive necrosis, not the chronic architectural remodeling seen in cirrhosis [1]. * **B. Hepatorenal syndrome:** While renal failure can occur in acetaminophen toxicity (due to direct tubular necrosis or as a complication of ALF), "Hepatorenal Syndrome" specifically refers to functional renal failure caused by portal hypertension and systemic vasodilation, typically seen in chronic cirrhosis [2]. * **D. Sinusoidal obstruction syndrome (Veno-occlusive disease):** This involves non-thrombotic obstruction of hepatic venules, typically associated with hematopoietic stem cell transplant, radiation, or pyrrolizidine alkaloids, rather than acetaminophen. **High-Yield Clinical Pearls for NEET-PG:** * **Antidote:** **N-acetylcysteine (NAC)**; it replenishes glutathione stores. It is most effective if given within 8 hours. * **Nomogram:** The **Rumack-Matthew Nomogram** is used to predict hepatotoxicity based on plasma acetaminophen levels (starting at 4 hours post-ingestion). * **Histology:** Characterized by **Centrilobular necrosis (Zone 3)** because this zone has the highest concentration of CYP450 enzymes that convert acetaminophen to NAPQI [2]. * **Prognosis:** The **King’s College Criteria** are used to determine the need for liver transplantation in acetaminophen-induced ALF (pH <7.3 or the triad of Grade III/IV encephalopathy, PT >100s, and Creatinine >3.4 mg/dL) [3].
Question 87: A 39-year-old carpenter develops confusion, vomiting, and blurring of vision about an hour after consuming two bottles of liquor. He has been brought to the emergency department. What should be administered?
- A. Naloxone
- B. Diazepam
- C. Flumazenil
- D. Ethyl alcohol (Correct Answer)
Explanation: **Explanation:** The clinical presentation of confusion, vomiting, and specifically **blurring of vision** (often described as "being in a snowstorm") after consuming illicit or adulterated liquor is classic for **Methanol poisoning** [1]. Methanol is metabolized by the enzyme alcohol dehydrogenase into formaldehyde and then formic acid, which causes metabolic acidosis and optic nerve damage [2]. **Why Ethyl Alcohol is the correct answer:** Ethanol (Ethyl alcohol) has a much higher affinity for the enzyme **alcohol dehydrogenase** than methanol does [1]. By administering ethanol, the enzyme is competitively inhibited, preventing the conversion of methanol into its toxic metabolites (formic acid). This allows the parent methanol to be excreted harmlessly by the kidneys or removed via hemodialysis. **Why the other options are incorrect:** * **A. Naloxone:** An opioid antagonist used to reverse respiratory depression in opioid overdose (e.g., heroin, morphine). It has no role in alcohol toxicity. * **B. Diazepam:** A benzodiazepine used to manage alcohol withdrawal (Delirium Tremens) or seizures, but it does not treat the underlying toxicity of methanol. * **C. Flumazenil:** A competitive benzodiazepine antagonist used to reverse benzodiazepine overdose. **High-Yield Clinical Pearls for NEET-PG:** * **Antidotes for Methanol/Ethylene Glycol:** Fomepizole (1st line) or Ethanol (2nd line). * **Cofactor Therapy:** Administer **Folate/Leucovorin** in methanol poisoning to enhance the breakdown of formic acid. * **Fundoscopy Finding:** Optic disc hyperemia and retinal edema are characteristic [3]. * **Metabolic Profile:** High anion gap metabolic acidosis (HAGMA) with an increased osmolar gap [3].
Question 88: Which of the following is NOT a recommended treatment for snakebite?
- A. Apply a firm bandage to occlude lymphatics.
- B. Make an incision over the wound. (Correct Answer)
- C. Reassure the patient.
- D. Immobilize the bitten part.
Explanation: ### Explanation The primary goal of snakebite management is to delay the systemic absorption of venom and prevent local tissue damage. **Why "Make an incision over the wound" is the correct answer:** Traditional "cut and suck" methods or making incisions over the bite site are **strongly contraindicated** [1]. These actions do not effectively remove venom; instead, they increase the risk of secondary bacterial infection, cause local tissue trauma, and can exacerbate bleeding—especially in vasculotoxic bites (e.g., Russell’s Viper) where the patient may have systemic coagulopathy [1]. **Analysis of Incorrect Options:** * **A. Apply a firm bandage to occlude lymphatics:** This is part of the **Pressure Immobilization Technique (PIT)** [1], [2]. Since venom primarily travels through the lymphatic system, a firm (but not arterial-occluding) bandage helps delay systemic spread, particularly in neurotoxic bites [4]. * **C. Reassure the patient:** This is a critical first step [1]. Anxiety increases heart rate and cardiac output, which accelerates the systemic circulation of the venom [2]. Reassurance helps keep the patient calm and reduces venom spread. * **D. Immobilize the bitten part:** Movement acts as a "pump" for the lymphatic system. Immobilizing the limb with a splint or sling significantly slows the movement of venom from the bite site to the central circulation [1], [4]. **High-Yield Clinical Pearls for NEET-PG:** * **The "Do Nots":** Do not apply a tight arterial tourniquet (causes ischemia/gangrene), do not apply ice, and do not use potassium permanganate [1]. * **ASV (Anti-Snake Venom):** In India, ASV is polyvalent (effective against the "Big Four": Cobra, Krait, Russell’s Viper, and Saw-scaled Viper) [3]. * **Neostigmine Test:** Used in neurotoxic bites (Cobra) to reverse neuromuscular blockade; always preceded by Atropine. * **20-minute Whole Blood Clotting Test (20WBCT):** The most reliable bedside test to diagnose coagulopathy in vasculotoxic bites.
Question 89: Gastric lavage is contraindicated in which of the following poisoning scenarios? 1. Kerosene poisoning 2. Organo-phosphorus poisoning 3. Corrosive poisoning 4. Iron poisoning
- A. 1 only
- B. 1 and 3 only (Correct Answer)
- C. 2 and 4 only
- D. 1, 2, 3 and 4
Explanation: **Explanation:** Gastric lavage is a decontamination procedure used to remove unabsorbed toxins from the stomach. However, it is strictly contraindicated in scenarios where the procedure itself poses a greater risk than the toxin absorption [1]. **1. Why Option B (1 and 3) is Correct:** * **Kerosene (Hydrocarbons):** These substances have low viscosity and high volatility. The primary risk is **aspiration pneumonitis**. Inserting a lavage tube or inducing vomiting can lead to the accidental inhalation of the hydrocarbon into the lungs, which is far more lethal than systemic absorption from the GI tract [2]. * **Corrosive Poisoning (Acids/Alkalis):** Corrosives cause liquefactive or coagulative necrosis of the esophageal and gastric mucosa. Passing a tube through weakened, friable tissue carries a high risk of **esophageal or gastric perforation** [1], [3]. Furthermore, re-exposure of the esophagus to the corrosive during lavage worsens the injury. **2. Why the other options are incorrect:** * **Organophosphorus (OP) Poisoning:** Gastric lavage is actually a **mainstay of treatment** if the patient presents within 1–2 hours. Since OP compounds are highly toxic and rapidly absorbed, removing them from the stomach is life-saving. * **Iron Poisoning:** While iron is not well-absorbed by activated charcoal, gastric lavage (specifically with large-bore tubes) can be performed in massive ingestions [4]. However, "Whole Bowel Irrigation" (WBI) is often preferred for iron tablets. It is not a contraindication. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindications for Lavage:** Corrosives, Hydrocarbons, Comatose patients (unless the airway is protected by an ET tube), and Sharp objects [1], [2]. * **Time Window:** Lavage is most effective within **60 minutes** of ingestion ("The Golden Hour"). * **Positioning:** During lavage, the patient should be in the **Left Lateral Recumbent position** with the head tilted down (Trendelenburg) to minimize aspiration risk [1]. * **Tube Used:** Ewald’s tube (large bore) is typically used for gastric lavage in adults.
Question 90: What is the mechanism of action of ethyl alcohol in methyl alcohol poisoning?
- A. Saturates alkaline phosphatase
- B. Blocks the formation of formaldehyde (Correct Answer)
- C. Inhibits calcium release
- D. All of the above
Explanation: **Explanation:** The toxicity of **methyl alcohol (methanol)** is not caused by the alcohol itself, but by its toxic metabolites. Methanol is metabolized in the liver by the enzyme **Alcohol Dehydrogenase (ADH)** into **formaldehyde**, which is then rapidly converted by aldehyde dehydrogenase into **formic acid** [2]. Formic acid is the primary toxin responsible for metabolic acidosis and retinal damage (blindness) [1], [2]. **Ethyl alcohol (ethanol)** acts as a competitive inhibitor of the enzyme Alcohol Dehydrogenase [1]. Ethanol has a much higher affinity (approximately 10–20 times greater) for ADH than methanol. By saturating this enzyme, ethanol effectively **blocks the formation of formaldehyde** and formic acid. This allows the parent methanol to be excreted harmlessly through the lungs and kidneys. **Analysis of Options:** * **Option A (Saturates alkaline phosphatase):** Incorrect. Alkaline phosphatase is a marker of hepatobiliary or bone disease and plays no role in alcohol metabolism. * **Option B (Correct):** Ethanol competes for ADH, preventing the oxidation of methanol into formaldehyde [2]. * **Option C (Inhibits calcium release):** Incorrect. While methanol poisoning can lead to hypocalcemia (rarely), ethanol's therapeutic mechanism is unrelated to calcium signaling [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Antidotes:** Fomepizole is now the preferred antidote (it also inhibits ADH) because it does not cause CNS depression, unlike ethanol [1]. * **Classic Presentation:** "Snowstorm vision" or blurred vision, high anion gap metabolic acidosis (HAGMA), and an increased osmolar gap [3]. * **Key Metabolite:** Formic acid (causes optic papillitis and putaminal necrosis) [1]. * **Cofactor Therapy:** Folate (Leucovorin) is administered to enhance the breakdown of formic acid into CO₂ and water.
Practice by Chapter
General Principles of Toxicology
Practice Questions
Antidotes and Specific Therapies
Practice Questions
Drug Overdose Management
Practice Questions
Heavy Metal Poisoning
Practice Questions
Pesticide and Insecticide Poisoning
Practice Questions
Plant and Food Toxins
Practice Questions
Household Chemical Exposure
Practice Questions
Environmental Toxins
Practice Questions
Occupational Exposures
Practice Questions
Toxicological Screening and Diagnosis
Practice Questions
Extracorporeal Removal Techniques
Practice Questions
Poisoning Prevention Strategies
Practice Questions
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free