Forensic Toxicology Practice Questions

Q: The 'boiled lobster' appearance is seen in poisoning with:

Boric acid. **Explanation:** The **'boiled lobster' appearance** is a classic, high-yield clinical sign of **Boric acid poisoning**. This phenomenon occurs due to an intense, generalized erythematous skin rash that progresses to exfoliation (desquamation), giving the skin a bright red, scalded appearance similar to a boiled lobster. This is most commonly seen in infants or children following accidental ingestion or excessive topical application of boric acid powder. **Analysis of Options:** * **Boric Acid (Correct):** Toxic levels lead to gastrointestinal distress followed by a characteristic "boiled lobster" rash. The exfoliation can be so severe that it mimics Toxic Epidermal Necrolysis (TEN). * **Carbolic Acid (Phenol):** Characterized by **corrosive burns** that are typically grayish-white and painless (due to local anesthetic effect). It also causes "Ochronosis" (pigmentation) and "Carboluria" (greenish-black urine). * **Oxalic Acid:** Known for causing local irritation and systemic hypocalcemia (leading to tetany). It produces a **"coffee-ground" vomitus** due to the formation of acid hematin, but no specific red skin rash. * **H2SO4 (Sulfuric Acid):** A strong corrosive that causes deep, **charring (blackening)** of tissues due to its intense dehydrating action. It does not produce a generalized erythematous rash. **High-Yield Clinical Pearls for NEET-PG:** 1. **Boric Acid:** Look for the triad of vomiting/diarrhea, "boiled lobster" rash, and CNS irritability/seizures. 2. **Fatal Dose:** For Boric acid, it is approximately 15–20g in adults and 3–6g in infants. 3. **Vomitus Colors:** * H2SO4: Black (Charring) * Nitric Acid: Yellow (Xanthoproteic reaction) * Copper Sulfate: Blue/Green * Oxalic Acid: Coffee-ground (Acid hematin)

Q: The "Mellanby effect" is observed with which substance?

Alcohol. **Explanation** The **Mellanby effect** is a phenomenon specifically associated with **Alcohol (Ethanol)** consumption. It describes the observation that the behavioral and cognitive impairment caused by alcohol is more pronounced when blood alcohol concentrations (BAC) are **rising** (the absorption phase) than when they are **falling** (the elimination phase), even if the BAC is identical at both points. This suggests that the central nervous system develops a form of "acute tolerance" during a single drinking session. **Analysis of Options:** * **Alcohol (Correct):** The Mellanby effect highlights that clinical intoxication does not always correlate linearly with BAC; a person may appear more "drunk" shortly after their first few drinks than they do hours later at the same chemical level. * **Paracetamol (Incorrect):** Toxicity is primarily related to the depletion of glutathione and the accumulation of the toxic metabolite NAPQI, leading to hepatic necrosis. It does not exhibit acute behavioral tolerance. * **Aspirin (Incorrect):** Salicylate poisoning is characterized by respiratory alkalosis followed by metabolic acidosis and uncoupling of oxidative phosphorylation. * **LSD (Incorrect):** While LSD shows rapid tachyphylaxis (diminishing effect with repeated doses), the specific term "Mellanby effect" is not used to describe its pharmacodynamics. **High-Yield Clinical Pearls for NEET-PG:** * **Widmark’s Formula:** Used to calculate the amount of alcohol consumed based on BAC ($A = c \times p \times r$). * **McEwan’s Sign:** Loss of pupillary light reflex in alcoholic coma (pupils contract when stimulated but slowly dilate again). * **Legal Limit in India:** 30 mg/100 ml of blood (Section 185 of the Motor Vehicles Act). * **Metabolism:** Alcohol follows **Zero-order kinetics** (metabolized at a constant rate regardless of concentration).

Q: In cyanide poisoning, what should the specimen of blood be covered with to avoid evaporation?

Liquid paraffin. ### Explanation **Correct Answer: C. Liquid paraffin** **Mechanism and Rationale:** Cyanide is a highly volatile substance. In cases of suspected cyanide poisoning, blood samples must be collected and preserved with extreme care to prevent the escape of **hydrocyanic acid (HCN) gas**. **Liquid paraffin** is used because it is an inert, non-volatile oil that forms a physical seal (layer) over the surface of the blood. This layer acts as a barrier, preventing the evaporation of volatile cyanide compounds into the headspace of the container, thereby ensuring an accurate quantitative analysis during toxicological screening. **Analysis of Incorrect Options:** * **A. Saturated salt solution:** While used in some forensic contexts to preserve tissues (like skin for diatom testing), it does not provide a seal against volatility and may interfere with chemical extraction. * **B. Formalin:** This is a fixative used for histopathology. It should **never** be used for toxicology as it denatures proteins and chemically reacts with many poisons (including cyanide), making detection impossible. * **D. Acetone:** This is a volatile organic solvent. Adding it would contaminate the sample and potentially interfere with gas chromatography results. **High-Yield Clinical Pearls for NEET-PG:** * **Odor:** Classically described as **"Bitter Almonds"** (present in only ~60% of the population due to genetic ability to smell it). * **Post-mortem appearance:** The skin and viscera show a characteristic **bright cherry-red** discoloration due to high levels of oxyhemoglobin (cyanide inhibits cytochrome oxidase, preventing tissues from utilizing oxygen). * **Preservation:** Blood should be collected in a fluoride-oxalate tube, filled to the brim, and layered with liquid paraffin. * **Antidote:** The standard treatment is the **Cyanide Antidote Kit** (Amyl nitrite, Sodium nitrite, and Sodium thiosulfate) or **Hydroxocobalamin** (Cyanokit).

Q: Gastric lavage is contraindicated in which type of poisoning?

Kerosene. **Explanation:** The correct answer is **Kerosene (Option A)**. Gastric lavage is strictly contraindicated in hydrocarbon poisoning (like kerosene, petrol, and diesel) because these substances have **low viscosity and high volatility**. The primary risk is **aspiration pneumonia**. If gastric lavage is attempted, the kerosene can easily be aspirated into the respiratory tract, either during the procedure or via induced vomiting. Even a tiny amount of kerosene in the lungs can cause severe chemical pneumonitis, pulmonary edema, and lipoid pneumonia, which are far more life-threatening than the systemic effects of the poison in the stomach. **Analysis of Incorrect Options:** * **Organophosphorus (Option B):** Gastric lavage is a mainstay of treatment, even if the patient presents late, as these compounds undergo enterohepatic circulation. * **Arsenic (Option C):** Lavage is indicated to remove the unabsorbed irritant from the stomach. * **Morphine (Option D):** Lavage is indicated even in parenteral (injectable) morphine poisoning. This is because morphine is secreted into the stomach from the blood (gastric recycling), and removing it prevents reabsorption. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindications for Lavage:** Corrosives (risk of perforation), Hydrocarbons (risk of aspiration), and Comatose patients without airway protection (cuffed endotracheal tube). * **The "Stomach Wash" Tube:** Ewald’s tube or Boas’ tube is typically used. * **Specific Lavage Fluids:** * **Opioids:** Potassium permanganate (1:5000). * **Organophosphorus:** Normal saline or Sodium bicarbonate. * **Exception:** Lavage *can* be done in kerosene poisoning only if a cuffed endotracheal tube is in place to protect the airway, though it is rarely clinically necessary.

Q: Toxicity due to which of the following can be successfully treated with Atropine?

Inocybe. **Explanation:** The correct answer is **Inocybe**. This question tests your knowledge of mushroom poisoning (mycetism) and the specific pharmacological management of different fungal toxins. **1. Why Inocybe is correct:** Mushrooms of the genus *Inocybe* (and *Clitocybe*) contain high concentrations of **Muscarine**. Muscarine acts as a potent agonist at post-ganglionic parasympathetic receptors, leading to a "SLUDGE" syndrome (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis). Since **Atropine** is a competitive antagonist at muscarinic receptors, it serves as a specific physiological antidote, rapidly reversing the life-threatening bradycardia and bronchoconstriction. **2. Why the other options are incorrect:** * **Isoxazole (Option B):** Found in *Amanita muscaria*, these mushrooms contain Ibotenic acid and Muscimol. These act on GABA and Glutamate receptors, causing CNS excitation or depression. Atropine is generally avoided here as it may worsen the delirium. * **A. phalloides (Option C) & Galerina (Option D):** These contain **Amatoxins** (specifically alpha-amanitin), which inhibit RNA polymerase II, leading to hepatic and renal failure. Atropine has no role here; treatment involves supportive care, activated charcoal, and potentially Silibinin or N-acetylcysteine. **High-Yield Clinical Pearls for NEET-PG:** * **Early-onset symptoms ( 6 hours):** Usually Amatoxins (*A. phalloides*). High mortality due to fulminant hepatic failure. * **Antidote Rule:** Atropine is the drug of choice for **pure muscarinic poisoning** (Inocybe/Clitocybe) and **Organophosphate poisoning**, both of which present with similar cholinergic features.

Q: Kunkel's test is done to demonstrate the presence of which substance in blood?

Carbon monoxide. **Explanation:** **Kunkel’s Test (Tannic Acid Test)** is a qualitative chemical test used to detect **Carbon Monoxide (CO)** in the blood. In this test, blood is diluted and treated with 3% tannic acid. * **Positive Result:** Blood containing Carboxyhemoglobin (COHb) forms a **light pink or cherry-red precipitate**. * **Negative Result:** Normal blood (Oxyhemoglobin) forms a brownish-gray precipitate. This occurs because COHb is more stable and resistant to the precipitating action of tannic acid compared to normal hemoglobin. **Analysis of Incorrect Options:** * **Lead (A):** Lead poisoning (Plumbism) is typically diagnosed via blood lead levels or by observing **basophilic stippling** in RBCs. It does not react with tannic acid in this manner. * **Copper Sulfate (B):** While copper sulfate is a corrosive poison, its presence is usually identified through chemical analysis of gastric lavage or the "blue-green" discoloration of gastric mucosa, not Kunkel's test. * **Dhatura (C):** Dhatura is a deliriant poison containing alkaloids like hyoscine and atropine. Diagnosis is clinical (mydriasis, dry mouth, delirium) or via the **Mydriatic test** (cat’s eye test). **High-Yield Clinical Pearls for NEET-PG:** * **Other tests for CO:** Hoppe-Seyler’s test (using NaOH) and Spectroscopic examination (shows two absorption bands that do not merge with reducing agents). * **Post-mortem finding:** The most characteristic sign of CO poisoning is the **cherry-red discoloration** of the skin, mucous membranes, and blood. * **Mechanism:** CO has an affinity for hemoglobin **200–250 times greater** than oxygen, causing a leftward shift of the oxygen-dissociation curve.

Q: Which laboratory tests are used for lead poisoning?

All of the above. **Explanation:** Lead poisoning (Plumbism) affects multiple organ systems by interfering with enzyme activities, particularly those involved in heme synthesis. Laboratory diagnosis relies on both direct measurement of lead levels and indirect markers of metabolic disruption. * **Lead in urine (Option A):** While blood lead levels (BLL) are the gold standard for acute exposure, urinary lead excretion is a significant indicator of the total body burden. It is particularly useful in **chelation therapy** (e.g., the Calcium Disodium EDTA mobilization test) to assess the amount of lead available for excretion. * **Aminolevulinic acid (ALA) in urine (Option B):** Lead inhibits the enzyme **ALAD (ALA Dehydratase)**. This blockage causes a backup of substrates, leading to increased levels of ALA in the blood and its subsequent excretion in the urine. This is a sensitive indicator of early lead effect. * **Coproporphyrin in urine (Option C):** Lead interferes with the enzyme **Coproporphyrinogen oxidase**. This results in the accumulation of Coproporphyrin III, which is then excreted in the urine. This is a classic screening test for chronic lead exposure. Since all three parameters are established diagnostic markers used to confirm lead toxicity, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Blood Lead Level (BLL) is the most reliable indicator of recent exposure. * **Erythrocyte Protoporphyrin (EP):** Elevated EP levels (specifically Zinc Protoporphyrin) indicate chronic exposure and its effect on bone marrow. * **Hematology:** Look for **Basophilic stippling** (punctate basophilia) on a peripheral smear, which represents inhibited RNA degradation. * **Radiology:** "Lead lines" at the metaphysis of long bones in children. * **Burtonian Line:** A characteristic blue-purple line on the gums due to lead sulfide deposition.

Q: Cholera-like diarrhea is associated with which type of poisoning?

Arsenic poisoning. **Explanation:** **Arsenic poisoning** is the correct answer because acute arsenic toxicity classically presents with severe gastrointestinal distress that mimics **Cholera**. The underlying mechanism involves arsenic’s ability to cause intense capillary congestion and sub-mucosal damage in the gastrointestinal tract. This leads to the characteristic **"Rice-water stools"** (watery diarrhea containing mucus shreds), profound dehydration, and electrolyte imbalance, making it clinically indistinguishable from Cholera without a detailed history. **Analysis of Incorrect Options:** * **Copper poisoning:** Typically presents with **metallic taste**, blue-green vomitus, and "pea-soup" diarrhea. It is more commonly associated with intravascular hemolysis and jaundice. * **Lead poisoning:** Acute lead poisoning is rare; chronic exposure (Plumbism) is characterized by **constipation**, colicky abdominal pain (Lead colic), and a blue line on the gums (Burtonian line), rather than diarrhea. * **Mercury poisoning:** Acute ingestion causes corrosive gastroenteritis with **bloody diarrhea** (hemorrhagic colitis) and severe renal tubular necrosis, rather than cholera-like watery stools. **High-Yield Clinical Pearls for NEET-PG:** * **Arsenic vs. Cholera:** In Arsenic poisoning, purging follows vomiting; in Cholera, purging usually precedes vomiting. Arsenic also causes intense throat irritation and pain, which is absent in Cholera. * **Mee’s Lines:** White transverse bands on nails seen in chronic arsenic poisoning. * **Raindrop Pigmentation:** Hyperpigmentation of the skin seen in chronic arsenic toxicity. * **Antidote:** British Anti-Lewisite (BAL/Dimercaprol) is the drug of choice for acute arsenic poisoning.

Question 1

The 'boiled lobster' appearance is seen in poisoning with:

Accepted Answer

Boric acid

Answer

Carbolic acid

Answer

Oxalic acid

Answer

H2SO4 poisoning

Question 2

The "Mellanby effect" is observed with which substance?

Accepted Answer

Alcohol

Answer

Paracetamol

Answer

Aspirin

Answer

LSD

Question 3

In cyanide poisoning, what should the specimen of blood be covered with to avoid evaporation?

Accepted Answer

Liquid paraffin

Answer

Saturated salt solution

Answer

Formalin

Answer

Acetone

Question 4

Gastric lavage is contraindicated in which type of poisoning?

Accepted Answer

Kerosene

Answer

Organophosphorus

Answer

Arsenic

Answer

Morphine

Question 5

Toxicity due to which of the following can be successfully treated with Atropine?

Accepted Answer

Inocybe

Answer

Isoxazole

Answer

A.phalloides

Answer

Galerina

Question 6

Kunkel's test is done to demonstrate the presence of which substance in blood?

Accepted Answer

Carbon monoxide

Answer

Lead

Answer

Copper sulfate

Answer

Dhatura

Question 7

A previously healthy girl, sleeping on the floor, suddenly develops nausea, vomiting, abdominal pain, and quadriplegia at night. What is the most likely diagnosis?

Accepted Answer

Krait bite

Answer

Guillain-Barré syndrome

Answer

Poliomyelitis

Answer

Periodic paralysis

Question 8

Which laboratory tests are used for lead poisoning?

Accepted Answer

All of the above

Answer

Lead in urine

Answer

Aminolevulinic acid (ALA) in urine

Answer

Coproporphyrin in urine

Question 9

An arrow mark or bird foot mark on the center of a snake bite suggests which type of snake?

Accepted Answer

Saw-scaled viper

Answer

Pit viper

Answer

King cobra

Answer

Krait

Question 10

Cholera-like diarrhea is associated with which type of poisoning?

Accepted Answer

Arsenic poisoning

Answer

Copper poisoning

Answer

Lead poisoning

Answer

Mercury poisoning

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

On this page

Practice by Chapter

Want unlimited practice?