Forensic Toxicology — MCQs

Forensic Toxicology Indian Medical PG Practice Questions and MCQs

Question 831: Which of the following snakes is MOST known for venom containing neurotoxins?

A. Sea snake
B. Cobra
C. Krait (Correct Answer)
D. Viper

Explanation: ***Krait*** - Kraits (Bungarus species) are **MOST known for pure neurotoxic venom** with minimal or no local effects at the bite site. - Their venom contains **presynaptic and postsynaptic neurotoxins**, causing classic features of **flaccid paralysis**, ptosis, and respiratory failure. - **Clinical hallmark**: Often described as the prototype of **pure neurotoxic envenomation** with absent local signs (no swelling, no pain). - Among Indian snakes, kraits have the **highest case fatality rate** due to potent neurotoxicity. *Cobra* - Cobras (Naja species) do have **neurotoxic venom** causing paralysis and respiratory failure. - However, cobra venom contains **significant cytotoxic components** causing marked **local tissue necrosis**, pain, and swelling at the bite site. - This mixed venom profile (neurotoxic + cytotoxic) makes it less "purely" neurotoxic compared to kraits. *Sea snake* - Sea snakes have neurotoxic venom causing myotoxicity and paralysis. - Bites are **rare** due to limited human contact and docile nature. - Not as clinically recognized in Indian medical practice compared to terrestrial elapids. *Viper* - Vipers (Russell's viper, Saw-scaled viper) have predominantly **hemotoxic and cytotoxic venom**. - Cause **coagulopathy**, hemorrhage, tissue necrosis, and acute kidney injury. - **Not neurotoxic** - this is the key differentiating feature from elapids (kraits, cobras).

Question 832: Mees's lines are characteristic of:

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

Explanation: ***Arsenic poisoning*** - **Mees's lines** are characteristic transverse white bands that appear on the fingernails and toenails, strongly indicative of **arsenic poisoning**. - These lines result from a temporary disruption of nail matrix growth, which occurs during systemic illness or exposure to toxins like arsenic. *Lead poisoning* - **Lead poisoning** is typically associated with **Burton's line** (a blue line on the gums) and neurological symptoms like **foot drop** or **wrist drop**, not Mees's lines. - Other common signs include **abdominal pain** and **anemia**. *Copper poisoning* - **Copper poisoning** can cause **hepatolenticular degeneration** (Wilson's disease if genetic), leading to **Kayser-Fleischer rings** in the eyes, but not Mees's lines. - Acute copper toxicity might present with **nausea, vomiting**, and **diarrhea**. *Mercury poisoning* - **Mercury poisoning** (e.g., Minamata disease) is known for neurological symptoms such as **tremors**, **ataxia**, and **gingivitis**, commonly referred to as **"mad hatter" syndrome**. - It does not specifically manifest **Mees's lines** on the nails.

Question 833: Socrates was killed by which poison? (NEET 14)

A. Cyanide
B. Datura
C. Strychnine
D. Conium (Correct Answer)

Explanation: ***Conium*** - **Socrates** was famously executed by being forced to drink a cup of **hemlock**, which is derived from the **poison hemlock plant**, *Conium maculatum*. - The active principle in **hemlock** that causes its toxic effects is **coniine**, a neurotoxic alkaloid that leads to ascending paralysis and respiratory failure. *Cyanide* - **Cyanide** is a rapid-acting poison that inhibits cellular respiration, leading to tissue hypoxia. - While a potent poison, it is not the substance historically documented as being used to execute **Socrates**. *Datura* - **Datura** species contain **tropane alkaloids** such as scopolamine and atropine, which cause anticholinergic effects like delirium, hallucinations, and tachycardia. - This plant's poison profile and historical evidence do not match the circumstances of **Socrates'** death. *Strychnine* - **Strychnine** is a highly toxic alkaloid that causes severe muscular spasms, convulsions, and ultimately respiratory arrest due to its action on glycine receptors in the spinal cord. - The symptoms associated with **Socrates'** death, primarily ascending paralysis, are not consistent with **strychnine** poisoning.

Question 834: Poisoning with which of the following retards putrefaction:

A. Arsenic (Correct Answer)
B. Lead
C. Aluminium phosphide
D. Copper

Explanation: ***Arsenic*** - **Arsenic** is a known **preservative** of tissues due to its ability to inhibit bacterial growth and enzyme activity, thereby retarding putrefaction. - In cases of arsenic poisoning, the decomposition of a body may be noticeably slower, and the tissues can appear unusually well-preserved. *Lead* - While **lead** is a heavy metal and can have toxic effects, it is not primarily known for its ability to significantly **retard putrefaction**. - Its toxic mechanisms do not involve direct inhibition of bacterial and enzymatic processes in a way that typically preserves tissues post-mortem. *Aluminium phosphide* - **Aluminium phosphide** is a highly toxic pesticide that can cause rapid death, but it does not have properties that actively **retard the process of putrefaction**. - Its mechanism of toxicity primarily involves the release of phosphine gas, which causes cellular damage, rather than tissue preservation. *Copper* - **Copper**, another heavy metal, has antimicrobial properties but is not recognized as an agent that significantly **retards putrefaction** in the same manner as arsenic. - Its acute and chronic toxic effects do not typically lead to the preservation of tissues after death.

Question 835: Which of the following is not a feature of Organophosphate poisoning?

A. Lacrimation
B. Vomiting
C. Salivation
D. Mydriasis (Correct Answer)

Explanation: ***Mydriasis*** - Organophosphate poisoning leads to **cholinergic crisis**, which causes **miosis** (pinpoint pupils) due to excessive parasympathetic stimulation of the pupillary constrictor muscles. - **Mydriasis** (pupil dilation) is characteristic of **anticholinergic poisoning** or sympathetic overactivity, which is the opposite effect. *Lacrimation* - Organophosphates inhibit **acetylcholinesterase**, leading to an accumulation of **acetylcholine** at cholinergic synapses. - This excess acetylcholine stimulates muscarinic receptors, causing an increase in gland secretions, including **lacrimation** (tearing). *Vomiting* - The muscarinic effects of organophosphate poisoning stimulate the **gastrointestinal tract**, leading to symptoms like nausea, abdominal cramps, diarrhea, and **vomiting**. - This is a common and significant feature of the cholinergic syndrome. *Salivation* - Similar to lacrimation, the excess acetylcholine due to organophosphate poisoning causes increased stimulation of salivary glands. - This results in excessive **salivation**, often manifesting as hypersalivation or drooling.

Question 836: Barium carbonate poisoning causes -

A. Gastrointestinal irritation
B. Muscular weakness (Correct Answer)
C. Cyanosis
D. Respiratory distress

Explanation: ***Correct: Muscular weakness*** - **Soluble barium salts** (barium chloride, barium nitrate, barium sulfide) are highly toxic when ingested, releasing Ba²⁺ ions - Barium blocks **potassium channels** in cell membranes, causing **intracellular shift of potassium** leading to profound **hypokalemia** - This results in **flaccid paralysis** and severe **muscular weakness**, which is the **hallmark feature** of barium poisoning - Can progress to **paralysis of respiratory muscles**, making it life-threatening - **Note:** Barium carbonate itself is **insoluble** and relatively non-toxic; toxicity occurs when converted to soluble forms in stomach acid *Incorrect: Gastrointestinal irritation* - While mild GI symptoms (nausea, vomiting, diarrhea) may occur, they are **not the dominant feature** - The primary toxicity is **neuromuscular** rather than gastrointestinal - GI irritation, when present, is overshadowed by the dramatic muscular manifestations *Incorrect: Cyanosis* - Cyanosis is not a primary feature of barium poisoning - May occur **secondarily** if respiratory muscle paralysis is severe enough to cause hypoxemia - Not a characteristic or early sign *Incorrect: Respiratory distress* - Respiratory distress occurs due to **paralysis of respiratory muscles** from hypokalemia - This is a **complication** of the muscular weakness, not the primary manifestation - While serious and potentially fatal, it represents progression of the neuromuscular toxicity

Question 837: Yellow discoloration of skin and mucosa is seen in poisoning with:

A. Phosphoric acid
B. Sulphuric acid
C. Nitric acid (Correct Answer)
D. Nitrous oxide

Explanation: ***Nitric acid*** - **Nitric acid** causes a characteristic **yellow discoloration** of the skin and mucous membranes due to the formation of **xanthoproteic acid**. - This reaction occurs when nitric acid comes into contact with proteins, nitrating the aromatic amino acids (tyrosine, tryptophan, and phenylalanine). *Phosphoric acid* - **Phosphoric acid** burns, if severe, can cause skin irritation with redness and blistering, but typically do not result in a distinct yellow discoloration. - While corrosive, its mechanism of tissue damage differs from nitric acid's specific reaction with proteins. *Sulphuric acid* - **Sulphuric acid** is a potent dehydrating agent and corrosive acid that causes severe burns, often appearing **black or brown (eschar)** due to tissue coagulation and carbonization. - It does not produce the specific yellow discoloration seen with nitric acid. *Nitrous oxide* - **Nitrous oxide** is an inhalational anesthetic and analgesic, and its overdose can lead to **hypoxia**, dizziness, and potential bone marrow suppression with chronic abuse. - It does not cause any form of skin or mucosal discoloration; its effects are systemic and neurological.

Question 838: Green colored urine is seen after ingestion of:

A. Organophosphorus
B. Phenol (Correct Answer)
C. Copper sulphate
D. Cyanide

Explanation: ***Phenol*** - Ingestion of **phenol** can lead to green-colored urine due to the formation of oxidation products, such as **hydroquinone** and **catechol**, which are excreted in the urine. - The green discoloration is a distinct toxicological sign associated with systemic phenol absorption. *Organophosphorus* - **Organophosphorus** poisoning primarily causes cholinergic symptoms like miosis, bradycardia, bronchorrhea, and muscle fasciculations. - It does not typically lead to a change in urine color; the urine usually remains clear or amber. *Copper sulphate* - **Copper sulfate** poisoning can cause symptoms like vomiting, abdominal pain, diarrhea, and potentially kidney damage. - While it can cause renal dysfunction, it does not typically result in green urine discoloration. *Cyanide* - **Cyanide** poisoning is characterized by rapid onset of symptoms affecting the cardiovascular, respiratory, and central nervous systems, leading to cellular hypoxia. - Urine color is not a characteristic feature of cyanide poisoning; it usually remains normal or slightly discolored due to other complications like rhabdomyolysis in severe cases.

Question 839: Acts both as poison and antidote:

A. Mercuric chloride
B. Silver chloride
C. Copper sulfate (Correct Answer)
D. Thallium arsenate

Explanation: ***Copper sulfate*** - **Copper sulfate** acts both as a **poison and antidote**, demonstrating dual properties. - In **large doses**, it is toxic, causing **gastrointestinal distress**, **hepatotoxicity**, **nephrotoxicity**, and potentially death. - Historically, it was used in **small controlled doses as an emetic** (to induce vomiting) in cases of poisoning, acting as an antidote by expelling ingested toxins. - **Note**: Its use as an emetic is now **outdated** due to safety concerns, but it remains the classic example of a substance with both toxic and therapeutic properties. *Mercuric chloride* - **Mercuric chloride** is a highly toxic compound acting primarily as a **corrosive poison**, causing severe damage to the **gastrointestinal tract** and kidneys. - It does not possess any antidote properties and requires aggressive **chelation therapy** for treatment. *Silver chloride* - **Silver chloride** is of **low toxicity** due to its insolubility in water and biological fluids. - While chronic exposure can cause **argyria** (bluish skin discoloration), it has no antidote properties. *Thallium arsenate* - **Thallium arsenate** contains two highly toxic elements (**thallium** and **arsenic**), both potent poisons affecting multiple organ systems. - Used in **pesticides** and **rodenticides** due to its toxicity, it has no beneficial or antidote properties.

Question 840: Which of the following snakes is most commonly associated with hematologic abnormalities following envenomation?

A. Sea snake
B. Krait
C. Viper (Correct Answer)
D. Cobra

Explanation: ***Correct Answer: Viper*** - **Viper venom** contains **hemotoxic components** including **metalloproteinases** and **serine proteinases** that directly activate clotting factors - This leads to **consumptive coagulopathy** characterized by **thrombocytopenia**, **hypofibrinogenemia**, and prolonged coagulation times - Clinical manifestations include spontaneous **bleeding**, **ecchymoses**, **hemorrhage** at the bite site, and in severe cases, **disseminated intravascular coagulation (DIC)** - Viper envenomation is the **classic cause** of hematologic abnormalities among snake bites *Incorrect: Sea snake* - Sea snake venoms are primarily **neurotoxic** and **myotoxic**, causing paralysis and muscle damage - While they can cause **rhabdomyolysis** and subsequent **renal failure**, significant primary hematologic abnormalities are not their hallmark feature *Incorrect: Krait* - Krait venom is predominantly **neurotoxic**, leading to **flaccid paralysis** and **respiratory failure** - Does not typically cause the significant widespread **coagulopathies** seen with viper envenomation *Incorrect: Cobra* - Cobra venom primarily contains **neurotoxins** and **cytotoxins**, causing **paralysis**, **tissue necrosis**, and localized pain - While some cobras can cause minor local bleeding, they do not generally induce the severe and systemic **hematologic abnormalities** characteristic of viper bites

Practice by Chapter

General Principles of Toxicology

Practice Questions

Corrosive Poisons

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Metallic Poisons

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Non-Metallic Poisons

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Organic Irritant Poisons

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Neurotic Poisons

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Cardiac Poisons

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Asphyxiant Poisons

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Food Poisoning

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Drug Abuse and Dependence

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Analytical Toxicology Methods

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Interpretation of Toxicology Results

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