Toxicology and Overdose Management — MCQs
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A farmer was sleeping in the field, and he felt a sting on his leg. He saw something moving away quickly. He then got drowsy and was taken to the hospital. He developed pain around the site and continued to bleed profusely from the wound site. The wound became red with blisters. Which of the following is the most likely cause?
A female patient has been on lithium for bipolar disorder for 6 months. After fasting for several days due to religious reasons, she presents with seizures, tremors, confusion, and weakness. What is the most appropriate investigation to diagnose her condition?
What is the immediate emergency treatment for carbon monoxide (CO) poisoning?
Cafe coronary most commonly occurs when a person is:
What is the most appropriate initial management for paralysis resulting from organophosphorus poisoning?
A 25-year-old male patient presents with ingestion of antifreeze solution. His arterial blood gas analysis report is as follows: pH = 7.20 Anion gap = 15 PCO2 = 25 HCO3 = 10 What is the most likely diagnosis?
A 25-year-old woman presents with recurrent abdominal pain and anaemia. Peripheral blood smear shows basophilic stippling of the red blood cells. What is the most likely diagnosis?
Intra-arterial calcium gluconate infusion is used in the management of burns caused by which of the following?
All are true regarding methanol poisoning except.
Which of the following is NOT a recommended primary management option for a patient with a snake bite?
Toxicology and Overdose Management Indian Medical PG Practice Questions and MCQs
Question 171: A farmer was sleeping in the field, and he felt a sting on his leg. He saw something moving away quickly. He then got drowsy and was taken to the hospital. He developed pain around the site and continued to bleed profusely from the wound site. The wound became red with blisters. Which of the following is the most likely cause?
- A. Viper bite (Correct Answer)
- B. Cobra bite
- C. Wasp sting
- D. Scorpion sting
Explanation: ***Viper bite*** - **Viper venom** is predominantly **hemotoxic**, causing local tissue damage (pain, redness, blistering, bleeding) and systemic effects like **coagulopathy**, leading to profuse bleeding [1]. - The rapid onset of drowsiness, local pain, bleeding, and blistering are classic signs of **viper envenomation** [1]. *Cobra bite* - **Cobra venom** is primarily **neurotoxic**, leading to **flaccid paralysis**, ptosis, and respiratory failure, rather than significant local tissue destruction or profuse bleeding [1]. - While local swelling and pain may occur, extensive blistering and significant bleeding are less characteristic compared to viper bites [1]. *Wasp sting* - A **wasp sting** causes localized pain, swelling, and redness, and may lead to an **anaphylactic reaction** in sensitive individuals [2]. - It does not typically cause profuse, prolonged bleeding or extensive blistering at the wound site as seen here [2]. *Scorpion sting* - **Scorpion stings** typically cause intense localized pain, paresthesias, and sometimes systemic symptoms like hypertension, tachycardia, and neurological effects [3]. - They do not typically cause widespread **hemorrhagic symptoms** or significant local blistering and extensive bleeding as described [3].
Question 172: A female patient has been on lithium for bipolar disorder for 6 months. After fasting for several days due to religious reasons, she presents with seizures, tremors, confusion, and weakness. What is the most appropriate investigation to diagnose her condition?
- A. Serum electrolytes
- B. Serum lithium levels (Correct Answer)
- C. ECG
- D. MRI
Explanation: **Serum lithium levels** - The patient's symptoms (seizures, tremors, confusion, weakness) are classic for **lithium toxicity**. - **Fasting** can lead to dehydration and electrolyte imbalance, which can increase lithium concentrations and toxicity [1]. *Serum electrolytes* - While **electrolyte imbalances** can occur with fasting and contribute to symptoms, measuring serum electrolytes alone will not directly diagnose lithium toxicity. - Electrolyte disturbances might be a predisposing factor or a concomitant issue, but not the primary diagnostic test for lithium toxicity itself [1]. *ECG* - An **ECG** can reveal cardiac effects of lithium toxicity, such as T-wave flattening or inversion, but it is not the most appropriate direct diagnostic test for the condition itself. - ECG changes are secondary manifestations and may not always be present or specific. *MRI* - While an **MRI** of the brain might be considered to rule out other causes of neurological symptoms like a stroke or brain lesion, it is not the initial or most appropriate investigation for suspected lithium toxicity. - The clinical picture strongly points to a pharmacological cause, making laboratory tests more relevant first-line diagnostics than imaging.
Question 173: What is the immediate emergency treatment for carbon monoxide (CO) poisoning?
- A. 5% CO2 inhalation
- B. 10% CO2 inhalation
- C. High flow O2 (Correct Answer)
- D. Nitroglycerine
Explanation: ***High flow O2*** - **High-flow oxygen** is the immediate emergency treatment for CO poisoning because it helps to displace CO from **hemoglobin**, thereby increasing oxygen delivery to tissues [1], [2]. - CO has a much **higher affinity** for hemoglobin than oxygen, so administering high concentrations of oxygen helps to reverse this binding and accelerate CO elimination [2]. *5% CO2 inhalation* - Administering **CO2** would worsen the patient's condition as it can cause **respiratory acidosis** and increase cerebral blood flow, potentially exacerbating CO toxicity. - CO2 inhalation would not effectively displace **carbon monoxide** from hemoglobin. *10% CO2 inhalation* - Similar to 5% CO2, **10% CO2 inhalation** would be detrimental, leading to significant **acidosis** and further compromising respiratory function. - This treatment does not address the primary issue of **carbon monoxide** binding to **hemoglobin** [2]. *Nitroglycerine* - **Nitroglycerine** is a vasodilator primarily used for conditions like **angina** or **heart failure**; it has no role in treating CO poisoning. - It would not help in displacing **carbon monoxide** or improving tissue oxygenation.
Question 174: Cafe coronary most commonly occurs when a person is:
- A. Eating large pieces of meat. (Correct Answer)
- B. Eating fish.
- C. Choking on food due to intoxication.
- D. Eating fatty food.
Explanation: ### Eating large pieces of meat - "Cafe coronary" is a term used to describe an episode of choking on food, often **large, poorly chewed pieces of meat**, mistaken for a cardiac event [1]. - It is commonly associated with individuals who may have difficulty chewing or have consumed **alcohol**, impairing their swallowing reflexes [1], [2]. ### Choking on food due to intoxication - While intoxication can exacerbate the risk, the primary cause of a "cafe coronary" is often the **improperly chewed food bolus**, not solely the intoxication itself [1], [2]. - Intoxication can impair the **gag reflex** and coordination, making choking more likely, but the specific food type is a key factor [1]. ### Eating fish - Choking on fish is typically associated with **fish bones**, which can cause a different type of airway obstruction or trauma, distinct from the large food bolus seen in a cafe coronary [1]. - While it can be serious, it doesn't fit the classic description of a cafe coronary, which typically involves a **meat-related obstruction** [1]. ### Eating fatty food - Fatty foods are not specifically linked to the "cafe coronary" phenomenon, which is characterized by mechanical obstruction due to **large, poorly chewed pieces of food** [2]. - While any food can cause choking, fatty foods themselves do not carry the same specific risk profile as **large meat chunks**.
Question 175: What is the most appropriate initial management for paralysis resulting from organophosphorus poisoning?
- A. Supportive care, including respiratory support (Correct Answer)
- B. Atropine to counteract muscarinic symptoms
- C. Oximes to reactivate acetylcholinesterase
- D. No specific antidote
Explanation: **Supportive care, including respiratory support** * **Paralysis** in organophosphorus poisoning (OPP) is often due to **nicotinic effects** at the neuromuscular junction, leading to respiratory muscle weakness and failure [2]. * **Respiratory support** through mechanical ventilation is crucial to maintain oxygenation and prevent complications while awaiting the effects of antidotal therapy [1], [2]. * *Atropine to counteract muscarinic symptoms* * **Atropine** primarily blocks **muscarinic receptors**, effectively treating symptoms like bradycardia, bronchorrhea, and miosis [2]. * It does **not reverse the nicotinic effects** responsible for muscle paralysis and respiratory failure. * *Oximes to reactivate acetylcholinesterase* * **Oximes (e.g., pralidoxime)** reactivate **acetylcholinesterase**, thereby addressing the underlying cause of acetylcholine accumulation [2]. * They are most effective if given **early** before irreversible aging of the enzyme occurs, but their effect on established paralysis can be limited without concurrent respiratory support [2]. * *No specific antidote* * This statement is incorrect; **atropine** and **oximes** are specific antidotes for organophosphorus poisoning [2]. * While these antidotes are vital, initial management prioritizing **airway and breathing support** is paramount due to the life-threatening respiratory paralysis [1].
Question 176: A 25-year-old male patient presents with ingestion of antifreeze solution. His arterial blood gas analysis report is as follows: pH = 7.20 Anion gap = 15 PCO2 = 25 HCO3 = 10 What is the most likely diagnosis?
- A. None of the options
- B. Normal anion gap metabolic acidosis
- C. High anion gap metabolic acidosis (Correct Answer)
- D. Both
Explanation: ***High anion gap metabolic acidosis*** - The patient has a **low pH (7.20)**, indicating **acidosis**. The **bicarbonate (HCO3-) is low (10 mEq/L)**, which confirms it is a metabolic acidosis [1]. - The **anion gap is calculated as Na+ - (Cl- + HCO3-)**. With the given anion gap of 15, which is above the normal range (typically 8-12 mEq/L), it indicates a **high anion gap metabolic acidosis** [2]. This is consistent with **antifreeze (ethylene glycol) ingestion**, which produces acidic metabolites [2]. *Normal anion gap metabolic acidosis* - This type of acidosis occurs when the **anion gap remains within the normal range** (8-12 mEq/L), even though blood pH is low. - It usually results from a **loss of bicarbonate**, often through the gastrointestinal tract (e.g., severe diarrhea) or via the kidneys (e.g., renal tubular acidosis) [3], with a compensatory increase in chloride. *None of the options* - This option is incorrect as the presented clinical and lab findings clearly point to a specific type of acid-base disturbance. - The calculated anion gap and the pH/bicarbonate levels provide sufficient information for diagnosis. *Both* - This option is incorrect because the patient's lab values, specifically the **elevated anion gap**, distinctly categorize the condition as a high anion gap metabolic acidosis, ruling out a normal anion gap metabolic acidosis. - An acid-base disorder cannot simultaneously be both high and normal anion gap.
Question 177: A 25-year-old woman presents with recurrent abdominal pain and anaemia. Peripheral blood smear shows basophilic stippling of the red blood cells. What is the most likely diagnosis?
- A. Coeliac disease
- B. Hookworm disease
- C. Sickle cell disease
- D. Lead poisoning (Correct Answer)
Explanation: ***Lead poisoning*** - The presence of **basophilic stippling** in red blood cells is a hallmark finding of lead poisoning, indicating abnormal hemoglobin synthesis [1]. - Symptoms such as **abdominal pain** and **anaemia** are common presentations due to lead's interference with heme synthesis and gastrointestinal function [1, 2]. *Hookworm disease* - Typically causes **iron deficiency anaemia** due to chronic blood loss, but does not result in basophilic stippling. - Clinical features include **abdominal pain** and **weight loss**, without specific RBC morphology changes seen in lead poisoning. *Coeliac disease* - Characterized by **malabsorption**, which can lead to **anaemia**, but is not associated with basophilic stippling of red blood cells. - Common symptoms include **diarrhea**, **bloating**, and nutritional deficiencies, rather than the specific hematological findings seen in lead poisoning. *Sickle cell disease* - Involves **sickling of red blood cells** and vaso-occlusive crises, but does not present with basophilic stippling or typical anaemia seen in lead poisoning. - Clinical manifestations include **pain episodes** and potential for **acute chest syndrome**, not recurrent abdominal pain as a primary feature.
Question 178: Intra-arterial calcium gluconate infusion is used in the management of burns caused by which of the following?
- A. Nitric acid
- B. Hydrofluoric acid (Correct Answer)
- C. Formic acid
- D. Hydrochloric acid
Explanation: Self-Correction/Note: While the provided references mention topical calcium gluconate gel for hydrofluoric acid burns, medical literature supports intra-arterial infusion for severe cases of this specific poisoning. ***Hydrofluoric acid*** - **Hydrofluoric acid (HF) burns** are unique due to the fluoride ion's ability to penetrate tissues and bind to calcium and magnesium, leading to severe pain, tissue destruction, and systemic toxicity like **hypocalcemia** and **cardiac arrhythmias**. For these burns, treatment may include topical application of 2.5% calcium gluconate gel [1]. - **Intra-arterial calcium gluconate** is a specific treatment for HF burns, providing calcium directly to the affected area to complex with fluoride, thus neutralizing its effects and alleviating pain. *Nitric acid* - **Nitric acid burns** are corrosive, causing coagulation necrosis and forming a characteristic yellow eschar [2]. - Management involves irrigation and supportive care; **calcium gluconate** is not a specific antidote. *Formic acid* - **Formic acid** is a strong organic acid that causes tissue denaturation and coagulation necrosis, similar to other strong acids. - Treatment focuses on irrigation and symptom management; **calcium gluconate** does not play a role. *Hydrochloric acid* - **Hydrochloric acid (HCl)** is a common strong acid that causes direct tissue destruction through protein denaturation and dehydration. - Its management involves copious irrigation and supportive care, not **calcium gluconate** infusion [2].
Question 179: All are true regarding methanol poisoning except.
- A. High anion gap metabolic acidosis is seen in severe cases
- B. Visual disturbances are commonly seen
- C. Hemodialysis is not required in methanol poisoning. (Correct Answer)
- D. Fomepizole acts by inhibiting alcohol dehydrogenase
Explanation: ***Hemodialysis is not required in methanol poisoning.*** - This statement is **false**, as hemodialysis is often a critical intervention in severe methanol poisoning to actively remove methanol and its toxic metabolites from the body, especially in cases of severe acidosis or organ damage [1]. - Due to the **small molecular size** of methanol and formic acid, **hemodialysis** is highly effective and recommended for rapid clearance. *High anion gap metabolic acidosis is seen in severe cases* - This statement is **true**; methanol is metabolized into **formic acid**, which accumulates and causes a characteristic **high anion gap metabolic acidosis** [2], [3]. - The acidosis is directly responsible for many of the severe clinical manifestations and is a key diagnostic feature [4]. *Visual disturbances are commonly seen* - This statement is **true**; methanol poisoning frequently leads to **visual disturbances**, including blurred vision, photophobia, and even **permanent blindness**, due to the toxic effect of formic acid on the **optic nerve** [2], [4]. - Funduscopic examination may reveal **optic disc hyperemia** or edema in severe cases [4]. *Fomepizole acts by inhibiting alcohol dehydrogenase* - This statement is **true**; **fomepizole** is the antidote for methanol poisoning and works by competing with methanol for the enzyme **alcohol dehydrogenase** [2], [3]. - By inhibiting alcohol dehydrogenase, fomepizole prevents the metabolism of methanol into its toxic metabolites, **formaldehyde** and **formic acid**, thus reducing toxicity [3].
Question 180: Which of the following is NOT a recommended primary management option for a patient with a snake bite?
- A. Wash with soap and water (Correct Answer)
- B. Reassure the patient
- C. Splinting and immobilization
- D. Keep the site of bite below heart level
Explanation: ***Wash with soap and water*** - Washing the bite with soap and water is **NOT** a recommended primary management option for a snake bite as it can spread the **venom**, potentially worsening the local effects and systemic absorption [1]. - The focus should be on **immobilization and minimizing movement** to restrict venom spread [1], [3]. *Splinting and immobilization* - **Immobilization** of the bitten limb is crucial to reduce venom dissemination through the **lymphatic system** [1], [2]. - This helps to **slow the absorption** of venom into the systemic circulation [1], [3]. *Reassure the patient* - **Anxiety and panic** can increase heart rate and metabolism, potentially accelerating venom absorption. - **Reassurance** helps to calm the patient, which can slow the spread of venom and improve cooperation with treatment [1], [2]. *Keep the site of bite below heart level* - Keeping the affected limb **below heart level** helps to reduce blood flow and, consequently, the systemic spread of venom [1]. - This simple maneuver can **delay the onset** of systemic toxic effects [1].
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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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