Forensic Toxicology — MCQs

Forensic Toxicology Indian Medical PG Practice Questions and MCQs

Question 911: What is the effect of strychnos nux vomica poisoning on a patient's consciousness?

A. Becomes unconscious within an hour
B. Becomes unconscious only in severe cases
C. Remains conscious throughout the poisoning (Correct Answer)
D. Becomes unconscious immediately after exposure

Explanation: ***Remains conscious throughout the poisoning*** - Patients poisoned with **strychnine** (from *Strychnos nux vomica*) typically remain **fully conscious** and aware of their surroundings, even during severe convulsions. - This preservation of consciousness amidst intense muscular spasms is a **distinguishing and agonizing feature** of strychnine poisoning. *Becomes unconscious within an hour* - This statement is generally incorrect for strychnine poisoning, as the prominent feature is maintained consciousness alongside **neurological excitability**. - Loss of consciousness is not a **primary or direct effect** of strychnine, though severe complications could indirectly affect it. *Becomes unconscious only in severe cases* - While extreme metabolic derangements or secondary complications (e.g., severe hypoxia from prolonged seizures) might eventually lead to altered consciousness, the **direct pharmacological action** of strychnine does not cause unconsciousness. - The patient remains conscious even through the most severe and life-threatening **tetanic spasms**. *Becomes unconscious immediately after exposure* - Strychnine primarily acts as an **antagonist to glycine receptors** in the spinal cord and brainstem, leading to exaggerated reflexes and muscle overactivity, not immediate unconsciousness. - The onset of symptoms, including muscular spasms, typically occurs within **15-30 minutes** of exposure, with consciousness generally preserved.

Question 912: Which heavy metal is the most common cause of poisoning worldwide?

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

Explanation: ***Arsenic*** - **Arsenic poisoning** is a significant global health concern, primarily due to contaminated groundwater used for drinking and agriculture, particularly in regions like Bangladesh, India, and parts of Southeast Asia. - Exposure can lead to a wide range of health effects, including **skin lesions**, nervous system disorders, and an increased risk of cancer, making it a major cause of morbidity and mortality worldwide. *Lead* - While **lead poisoning** is a serious public health issue, especially in children, its prevalence has significantly decreased in many developed countries due to the removal of lead from gasoline and paints. - Exposure is often occupational or from older residential sources, and though still a concern, it is not as widespread globally as arsenic contamination. *Mercury* - **Mercury poisoning** is often associated with industrial pollution, consumption of contaminated fish, and occupational exposure. - While severe and toxic, mercury exposure is generally more localized and less pervasive globally compared to arsenic in drinking water. *Cadmium* - **Cadmium poisoning** is primarily linked to industrial activities like battery manufacturing, mining, and through contaminated food sources. - It can cause kidney damage and bone disease but is generally considered less common as a global public health crisis compared to widespread arsenic contamination.

Question 913: In nux vomica poisoning, the posture commonly assumed by the spine is:

A. Opisthotonus (Correct Answer)
B. Emprosthotonus
C. Pleurosthotonus
D. B and C

Explanation: ***Opisthotonus*** - **Nux vomica poisoning** (strychnine) causes severe muscle spasms due to glycine receptor antagonism, leading to uncontrolled excitation of motor neurons. - **Opisthotonus** is the characteristic posture where the back is arched and the head and heels are bent backward, resembling a backward-facing arch. *Emprosthotonus* - **Emprosthotonus** involves the body arching forward, an extremely rare manifestation not typical for **strychnine poisoning**. - This posture is not characteristic of common clinical conditions and is distinctly different from the extensor-dominant spasms seen in nux vomica toxicity. *Pleurosthotonus* - **Pleurosthotonus** is a rare form of muscle spasm where the body is arched to one side. - This is not a characteristic presentation of muscle spasms induced by **nux vomica poisoning**, which primarily affects the extensor muscles symmetrically. *B and C* - Neither **emprosthotonus** nor **pleurosthotonus** are the most commonly assumed postures in nux vomica poisoning. - The dominant and most recognizable posture is **opisthotonus**, reflecting the widespread and severe extensor muscle spasm.

Question 914: Barium carbonate poisoning causes: NEET 13

A. Muscular weakness (Correct Answer)
B. Respiratory issues
C. Gastrointestinal symptoms
D. Bluish discoloration of skin

Explanation: ***Muscular weakness*** - Barium ions **block potassium channels** in muscle cells, leading to an intracellular shift of potassium. - This results in **hypokalemia**, which directly causes **muscle weakness** and paralysis, including cardiac muscle dysfunction. *Respiratory issues* - While severe barium poisoning can indirectly affect respiration due to muscle paralysis, it's not the primary or initial presenting symptom. - The direct effect on airways or lung tissue is minimal compared to the systemic effects. *Gastrointestinal symptoms* - **Nausea, vomiting, abdominal pain**, and diarrhea are common initial symptoms of barium carbonate ingestion. - However, these are general signs of poisoning and not the most distinctive or severe consequence associated with barium's specific toxicity. *Bluish discoloration of skin* - Bluish discoloration, or **cyanosis**, typically indicates **hypoxia** or methemoglobinemia. - Barium poisoning does not directly cause cyanosis; any bluish tint would be a secondary effect of severe respiratory muscle paralysis and inadequate oxygenation in critical cases.

Question 915: Tetany is caused by poisoning with which of the following substances?

A. Oxalic acid (Correct Answer)
B. Carbolic acid
C. Sulfuric acid
D. Nitric acid

Explanation: ***Oxalic acid*** - **Oxalic acid** binds with **calcium** in the body to form **insoluble calcium oxalate crystals**, which are then deposited in the renal tubules. - This **chelation** of calcium leads to **hypocalcemia**, causing symptoms such as **tetany**, muscle cramps, and seizures. *Carbolic acid* - **Carbolic acid** (phenol) is a corrosive agent primarily causing local tissue damage, burns, and systemic toxicity affecting the **cardiovascular and central nervous systems**. - It does not primarily lead to **hypocalcemia** or **tetany** as a direct mechanism of action. *Sulfuric acid* - **Sulfuric acid** is a strong corrosive mineral acid that causes severe chemical burns on contact with tissues. - Its systemic effects are mainly due to **acidosis** and organ damage from its corrosive action, without a direct link to **hypocalcemia** or **tetany**. *Nitric acid* - **Nitric acid** is also a strong corrosive acid that causes liquefactive necrosis and deep burns upon contact. - While systemic absorption can lead to **metabolic acidosis** and organ damage, it does not directly cause **hypocalcemia** or **tetany**.

Question 916: Widmark's formula helps in the measurements of blood level of:

A. Alcohol (Correct Answer)
B. Barbiturate drugs
C. Cocaine derivatives
D. Benzodiazepine medications

Explanation: ***Alcohol*** - **Widmark's formula** is a widely used method to estimate an individual's **blood alcohol concentration (BAC)** based on the amount of alcohol consumed, body weight, and gender. - This formula helps in forensic toxicology and clinical settings to assess the level of **intoxication**. *Barbiturate drugs* - The levels of **barbiturate drugs** are typically measured using techniques like **gas chromatography-mass spectrometry (GC-MS)** or **high-performance liquid chromatography (HPLC)**. - While various formulas might exist for pharmacokinetic modeling of specific drugs, Widmark's formula is not applicable to barbiturates. *Cocaine derivatives* - **Cocaine and its metabolites** (e.g., benzoylecgonine) are detected and quantified in biological samples (blood, urine) using analytical methods such as **immunoassay**, **GC-MS**, or **LC-MS/MS**. - Widmark's formula is specific to alcohol metabolism and distribution, not cocaine. *Benzodiazepine medications* - The measurement of **benzodiazepine concentrations** in blood is predominantly done using **chromatographic methods** (e.g., GC-MS, LC-MS/MS) due to their complex metabolism and structural diversity. - Widmark's formula is not designed to calculate levels of benzodiazepines.

Question 917: Which of the following poisonings presents with abdominal pain, diarrhea, Mees lines on nails, and myelosuppression?

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

Explanation: ***Arsenic*** - **Arsenic poisoning** is characterized by gastrointestinal symptoms like severe **abdominal pain** and **diarrhea**, as well as dermatological signs such as **Mees lines** (transverse white bands on fingernails). - It also causes **myelosuppression**, leading to anemia, leukopenia, and thrombocytopenia, and can affect the cardiovascular and nervous systems. *Lead* - **Lead poisoning** typically presents with diffuse **abdominal pain** (lead colic), **constipation** (not diarrhea), and neurological symptoms like **foot drop** and **encephalopathy**. - While it can cause anemia due to impaired heme synthesis, **Mees lines** and significant myelosuppression are not primary features. *Alcohol* - **Alcohol intoxication** or chronic alcoholism primarily affects the central nervous system, liver, and pancreas, leading to symptoms like **ataxia**, **hepatitis**, and **pancreatitis**. - It does not cause **Mees lines** or the specific combination of severe gastrointestinal issues and myelosuppression seen with arsenic. *Mercury* - **Mercury poisoning** typically manifests with neurological symptoms (tremors, emotional lability, **peripheral neuropathy**), stomatitis, and renal dysfunction. - While it can cause gastrointestinal upset, **Mees lines** and **myelosuppression** are not characteristic features of mercury toxicity.

Question 918: The odour of cyanide is similar to?

A. Rotten egg
B. Fish
C. Fruity
D. Bitter almond (Correct Answer)

Explanation: ***Bitter almond*** - The classic description of **cyanide odor** is that of **bitter almonds**. This specific scent is a key indicator during forensic investigations or in cases of suspected poisoning. - However, not everyone can detect this smell due to a **genetic trait** that affects the ability to perceive it. *Rotten egg* - A **rotten egg** odor is characteristic of **hydrogen sulfide (H2S)**, a highly toxic gas. - This gas is often produced by the decomposition of organic matter and does not indicate cyanide exposure. *Fish* - A **fishy odor** is typically associated with compounds like **amines**, such as **trimethylamine**, which are found in decomposing fish or certain medical conditions like **trimethylaminuria**. - This smell is distinct from the bitter almond scent of cyanide. *Fruity* - A **fruity odor** can be associated with various substances, including **ketones** in conditions like **diabetic ketoacidosis** or certain **volatile organic compounds**. - This scent is not characteristic of cyanide poisoning.

Question 919: Gastric lavage is contraindicated in which of the following?

A. Organophosphorus Poisoning
B. Dhatura poisoning
C. Arsenic poisoning
D. Kerosene poisoning (Correct Answer)

Explanation: ***Kerosene poisoning*** - Gastric lavage is contraindicated in **kerosene poisoning** due to the high risk of **aspiration pneumonitis**. - Kerosene is a **hydrocarbon**, and aspiration of even small amounts can cause severe lung damage. *Arsenic poisoning* - **Gastric lavage** can be performed in arsenic poisoning, especially if the ingestion occurred recently, to remove unabsorbed toxin. - Activated charcoal is less effective for arsenic, making lavage a more relevant intervention in acute settings. *Organophosphorus Poisoning* - Gastric lavage is generally recommended within an hour of ingestion for **organophosphorus poisoning** to remove the toxic substance. - This helps reduce systemic absorption and mitigate the severe **cholinergic crisis** caused by these agents. *Dhatura poisoning* - **Gastric lavage** is indicated in dhatura poisoning, particularly if presenting within a few hours of ingestion, to remove unabsorbed **atropine-like alkaloids**. - This helps in reducing the **anticholinergic effects** and improving patient outcomes.

Question 920: Which of the following conditions is not caused by chronic arsenic poisoning?

A. Mesothelioma (Correct Answer)
B. Hyperkeratosis of skin
C. Anemia
D. Mixed sensory and motor neuropathy

Explanation: ***Mesothelioma*** - **Mesothelioma** is strongly linked to **asbestos exposure**, not chronic arsenic poisoning. - It is a rare and aggressive cancer that affects the lining of the lungs, abdomen, or heart. *Hyperkeratosis of skin* - **Chronic arsenic poisoning** is well-known to cause **hyperkeratosis**, particularly on the palms and soles, leading to thickened and hardened skin. - This dermatological manifestation is a classic sign of long-term arsenic exposure. *Anemia* - **Chronic arsenic exposure** can lead to **bone marrow suppression** and **hemolysis**, both of which contribute to the development of **anemia**. - It can also impair erythropoiesis, further exacerbating reduced red blood cell production. *Mixed sensory and motor neuropathy* - **Arsenic** is a potent neurotoxin that can cause **peripheral neuropathy**, manifesting as both **sensory and motor deficits**. - This typically presents as a "stocking-glove" distribution of numbness, tingling, pain, and weakness.

Practice by Chapter

General Principles of Toxicology

Practice Questions

Corrosive Poisons

Practice Questions

Metallic Poisons

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Non-Metallic Poisons

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Organic Irritant Poisons

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Neurotic Poisons

Practice Questions

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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