Toxicology and Overdose Management — MCQs

Toxicology and Overdose Management Indian Medical PG Practice Questions and MCQs

Question 141: Two of 3 family members have dinner at a local restaurant and, within 48 hours, start experiencing double vision, difficulty in swallowing and speaking, and breathing problems. These symptoms are consistent with which of the following?

A. Activation of cyclic AMP
B. Invasion of the gut epithelium by an organism
C. Endotoxin shock
D. Ingestion of a neurotoxin (Correct Answer)

Explanation: ***Ingestion of a neurotoxin*** - The symptoms of **double vision**, **difficulty swallowing (dysphagia)**, **difficulty speaking (dysarthria)**, and **breathing problems** are classic manifestations of **botulism**, a severe form of food poisoning caused by the **botulinum neurotoxin** [1, 2]. - The rapid onset (within 48 hours) and association with a shared meal at a restaurant strongly suggest exposure to a preformed toxin, which is characteristic of foodborne botulism [2]. *Activation of cyclic AMP* - This mechanism is characteristic of toxins like **cholera toxin** or **E. coli enterotoxin**, which cause **secretory diarrhea** by increasing fluid and electrolyte secretion in the gut. - It does not explain the neurological symptoms observed, such as double vision, dysphagia, or breathing difficulties [2]. *Invasion of the gut epithelium by an organism* - This mechanism is typical of diseases caused by invasive bacteria like *Salmonella*, *Shigella*, or some strains of *E. coli*, leading primarily to symptoms like **inflammatory diarrhea**, fever, and abdominal pain [2]. - It does not account for the specific neurological signs of cranial nerve dysfunction and paralysis. *Endotoxin shock* - **Endotoxin shock**, also known as septic shock, is caused by the release of **lipopolysaccharide (LPS)** from gram-negative bacteria, leading to a systemic inflammatory response. - Symptoms include **fever**, **hypotension**, **tachycardia**, and **multiorgan dysfunction**, not the specific neurological symptoms described here.

Question 142: A 3 yrs old child is brought to the emergency room by his parents after they found him having a generalized seizure at home. The child's breath smells of garlic, and he has bloody diarrhea, vomiting, and muscle twitching. Which poison is it likely that this child has encountered?

A. Thallium
B. Carbon monoxide
C. Arsenic (Correct Answer)
D. Lead

Explanation: **Arsenic** - **Arsenic poisoning** in children can present with a combination of **gastrointestinal distress** (bloody diarrhea, vomiting) [1], **neurological symptoms** (seizures, muscle twitching) [1], [3], and a characteristic **garlic-like odor** on the breath [1]. - The rapid onset of severe symptoms, including seizures, is consistent with acute arsenic toxicity [3]. *Thallium* - **Thallium poisoning** typically presents with **hair loss**, painful **neuropathy**, and gastrointestinal upset. - A garlic odor on the breath and acute seizures as prominent initial symptoms are not characteristic of thallium exposure. *Carbon monoxide* - **Carbon monoxide poisoning** would present with symptoms like **headache**, **dizziness**, nausea, and **cherry-red skin** in severe cases, but not a garlic odor or bloody diarrhea. - **Seizures** can occur, but the overall clinical picture, especially the garlic breath and bloody diarrhea, is inconsistent. *Lead* - **Lead poisoning** in children is often chronic, presenting with neurodevelopmental issues, **abdominal pain** (lead colic), **anemia**, and a **"lead line" on the gums** [2]. - While seizures can be a late manifestation of severe lead encephalopathy [2], the acute presentation with garlic breath, bloody diarrhea, and rapid-onset seizures is not typical for lead exposure.

Question 143: All of the following are causes of Rhabdomyolysis, Except:

A. Hypokalemia
B. Crush injury
C. Hyperphosphatemia (Correct Answer)
D. Cocaine Intoxication

Explanation: ***Hyperphosphatemia*** - While **hyperphosphatemia** is a common **consequence** of rhabdomyolysis due to the release of intracellular phosphate from damaged muscle cells, it is not a **cause** of rhabdomyolysis itself. - It develops **after** muscle breakdown has already occurred, often contributing to acute kidney injury. *Hypokalemia* - **Severe hypokalemia** can lead to muscle weakness, paralysis, and in some cases, **rhabdomyolysis** due to altered membrane excitability and impaired muscle function. - This can occur through direct muscle cell damage or by making muscles more susceptible to injury from activity. *Crush injury* - **Crush injuries** directly damage muscle tissue through mechanical force, leading to widespread cell lysis and the release of intracellular contents. - This is a well-established and significant cause of **traumatic rhabdomyolysis**. *Cocaine Intoxication* - **Cocaine intoxication** can cause rhabdomyolysis through multiple mechanisms, including **hyperthermia**, **vasoconstriction** leading to muscle ischemia, and direct **myotoxicity**. - The elevated body temperature and increased muscle activity associated with cocaine use contribute to muscle breakdown.

Question 144: All of the following are treatments for snakebite, EXCEPT:

A. Incision over wound (Correct Answer)
B. Reassure the patient
C. Firm bandage to occlude lymphatic
D. Immobilization of bitten part

Explanation: ***Incision over wound*** - Incision over a **snakebite** is contraindicated as it can introduce infection, cause further tissue damage, and may worsen bleeding due to **coagulopathy** caused by some venoms [1]. - This practice has no proven benefit in removing venom and is associated with significant risks [1]. *Reassure the patient* - Reassurance is a crucial initial step as **fear and anxiety** can worsen the patient's condition, leading to symptoms like **tachycardia** and **hyperventilation** [2]. - A calm approach helps in assessing the patient effectively and preparing them for further medical intervention [2]. *Firm bandage to occlude lymphatic* - A **pressure immobilization bandage** can delay the systemic absorption of venom, particularly from elapid snakebites, by reducing **lymphatic flow** [1], [3]. - The bandage should be applied firmly, similar to an ankle sprain bandage, but not so tight as to impair **arterial circulation** [1]. *Immobilization of bitten part* - Immobilizing the bitten limb, preferably at or below heart level, helps to reduce the spread of venom by minimizing muscle movement and **lymphatic drainage** [1], [3]. - This is often achieved using a **splint** or sling along with the pressure bandage [1], [2].

Question 145: Pink disease is seen in

A. Lead poisoning
B. Cyanide poisoning
C. Carbon monoxide poisoning
D. Mercury poisoning (Correct Answer)

Explanation: ***Mercury poisoning*** - Pink disease, also known as **Acrodynia**, is a rare but severe manifestation of **chronic mercury poisoning** in infants and young children [2]. - Clinical features include a **pinkish-red rash** on the hands and feet, generalized erythema, irritability, photophobia, and hypotonia. *Lead poisoning* - Lead poisoning primarily affects the **nervous system**, **hematologic system**, and **kidneys** [1]. - Symptoms include abdominal pain, constipation, developmental delay, and a **lead line** on the gums, but not a characteristic pink rash [1]. *Cyanide poisoning* - Cyanide poisoning is an acute and rapidly progressing condition that interferes with **cellular respiration**, leading to hypoxia. - Typical signs include headache, dizziness, rapid breathing, and a **bright red flushing** of the skin, not pink disease. *Carbon monoxide poisoning* - Carbon monoxide poisoning occurs when CO binds to hemoglobin, forming **carboxyhemoglobin** and reducing oxygen transport. - Victims often present with a **cherry-red appearance** of the skin and mucous membranes due to carboxyhemoglobin, distinct from the pink rash of acrodynia.

Question 146: Which of the following is LEAST likely to cause hyperthermia?

A. Neuroleptic malignant syndrome
B. Phencyclidine use (Correct Answer)
C. Aspirin toxicity
D. None of the options

Explanation: ***Phencyclidine use*** - While PCP can lead to a *delirious state* and *agitation*, **hyperthermia** is not a primary or common direct toxic effect. - Its primary central nervous system effects are dissociative and hallucinogenic, and while **rhabdomyolysis** can occur (which can indirectly elevate temperature), direct **hyperthermia** is less characteristic than with the other listed conditions. *Neuroleptic malignant syndrome* - This is a severe, life-threatening reaction to **antipsychotic drugs** [1] characterized by **fever**, muscle rigidity, autonomic instability, and altered mental status [2]. - **Hyperthermia** is a hallmark symptom due to severe muscle rigidity and impaired thermoregulation [1], [3]. *Aspirin toxicity* - **Salicylate poisoning** directly causes **hyperthermia** by uncoupling oxidative phosphorylation, leading to increased metabolic rate and heat production. - It also stimulates the respiratory center, leading to **respiratory alkalosis**, and can cause metabolic acidosis. *None of the options* - This option is incorrect because **phencyclidine use** is indeed the least likely to cause hyperthermia among the choices provided. - The other conditions listed are well-known causes of significant **hyperthermia** [1], [3].

Question 147: CSF examination is most commonly indicated in:

A. Suspected bacterial meningitis (Correct Answer)
B. Suspected viral encephalitis
C. Suspected subarachnoid hemorrhage
D. Suspected tuberculous meningitis

Explanation: ***Suspected bacterial meningitis*** - A **lumbar puncture** to obtain **CSF for analysis** is crucial for diagnosing **bacterial meningitis**, as it provides definitive information on cell count, glucose, protein, and presence of bacteria [1]. - Early and accurate diagnosis is critical for initiating specific **antibiotic therapy** and preventing severe neurological sequelae or death. *Suspected viral encephalitis* - While CSF analysis is helpful in **viral encephalitis** to look for **lymphocytic pleocytosis**, elevated protein, and normal glucose, it is not the most common or primary indication compared to suspected bacterial meningitis which demands urgent and specific treatment decisions [2]. - **Neuroimaging (MRI)** is often more informative initially in viral encephalitis to look for parenchymal involvement. *Suspected subarachnoid hemorrhage* - In suspected **subarachnoid hemorrhage (SAH)**, a **CT scan of the head** is the initial imaging modality of choice. - Lumbar puncture is typically performed only if the **CT scan is negative** but clinical suspicion remains high, to look for **xanthochromia**, which indicates old blood products [4]. *Suspected tuberculous meningitis* - Although **CSF analysis** is essential for diagnosing **tuberculous meningitis**, specifically looking for **lymphocytic pleocytosis**, low glucose, and high protein, the diagnostic process involves more specialized tests like **CSF culture for acid-fast bacilli** (which can take weeks) or **PCR** [3]. - Its incidence is lower than bacterial meningitis in many regions, making it a less common indication for urgent CSF sampling in the general population compared to acute bacterial infection [5].

Question 148: A young girl has consumed barium carbonate with suicidal intent. She complains of generalized muscle weakness. The most likely electrolyte abnormality is:

A. Hyponatremia
B. Hypokalemia (Correct Answer)
C. Hypomagnesemia
D. Hypocalcemia

Explanation: **Hypokalemia** - Barium carbonate poisoning causes **hypokalemia** by blocking **potassium channels**, leading to an intracellular shift of potassium [1]. - **Generalized muscle weakness** is a classic symptom of significant hypokalemia, as potassium is crucial for normal muscle function [1]. *Hyponatremia* - **Hyponatremia** would typically present with neurological symptoms like confusion and seizures, or gastrointestinal issues, not primarily generalized muscle weakness. - While some toxins can affect sodium balance, barium toxicity is specifically known for its impact on potassium [1]. *Hypomagnesemia* - **Hypomagnesemia** can cause muscle weakness but is more commonly associated with symptoms like **tetany**, tremors, and cardiac arrhythmias, which are not the primary complaint here. - Barium carbonate does not directly cause hypomagnesemia; its primary mechanism of action involves potassium channels [1]. *Hypocalcemia* - **Hypocalcemia** is characterized by **neuromuscular irritability**, including muscle cramps, tetany, and paresthesias, rather than generalized weakness as the primary symptom. - Barium poisoning does not typically lead to significant hypocalcemia.

Question 149: Pink disease is seen due to

A. Arsenic poisoning
B. Internal resorption
C. Trauma
D. Mercury poisoning (Correct Answer)

Explanation: ***Mercury poisoning*** - **Pink disease**, also known as **acrodynia**, is a historical term for a childhood illness caused by chronic exposure to **mercury** [1]. - Symptoms include a characteristic pink rash on the hands and feet, irritability, photophobia, and hypotonia [1]. *Arsenic poisoning* - **Arsenic poisoning** can lead to symptoms like gastrointestinal distress, skin lesions (hyperkeratosis, melanosis), and neurological effects [2]. - It does not typically cause the characteristic pink rash and other signs associated with acrodynia. *Internal resorption* - **Internal resorption** is a dental condition where the dentin and cementum of a tooth are resorbed from within the pulp chamber or root canal. - This condition is localized to the tooth and is not associated with systemic symptoms or a widespread rash like pink disease. *Trauma* - **Trauma** refers to physical injury and can cause various localized or systemic effects depending on the nature and severity of the injury. - While trauma can lead to discoloration or rashes, it is not a direct cause of the specific syndrome known as pink disease (acrodynia).

Question 150: Which of the following is the MOST COMMON condition that can cause absent pupillary response, despite the patient not being brainstem dead?

A. Drug overdose (Correct Answer)
B. Hypothermia
C. Use of mydriatic eye drops
D. Severe structural damage to the eye

Explanation: ***Drug overdose*** - Certain drugs, particularly **opioids** and other central nervous system depressants, can cause **pinpoint pupils** that are unresponsive to light, mimicking neurological damage without brainstem death [1]. - This is a common presentation in emergency settings and must be differentiated from brainstem death [2]. *Hypothermia* - **Severe hypothermia** can cause sluggish or fixed pupils due to systemic effects on neural pathways [3]. - However, it is a less common cause than drug overdose for an absent pupillary response in a non-brain dead patient. *Use of mydriatic eye drops* - Mydriatic eye drops directly block parasympathetic innervation or stimulate sympathetic innervation to the iris, leading to **dilated and fixed pupils**. - While it can cause an absent pupillary response, it is usually due to medical intervention rather than a systemic condition mimicking brainstem death, and is therefore not the "most common" condition in general medical presentations. *Severe structural damage to the eye* - Direct **structural damage to the eye**, such as significant trauma, can impair the pupillary light reflex. - This is a localized problem and less common as a general condition causing absent pupillary response in the context of avoiding a brainstem death diagnosis.

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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