Forensic Toxicology Practice Questions

Q: Which of the following salts of cyanide is considered non-poisonous?

Potassium ferrocyanide. **Explanation:** The toxicity of cyanide compounds depends entirely on their ability to release the **free cyanide ion (CN⁻)**. The cyanide ion is a potent cellular poison that binds to the ferric iron ($Fe^{3+}$) of **cytochrome oxidase a3** in the mitochondria, inhibiting the electron transport chain and causing histotoxic hypoxia. **Why Potassium Ferrocyanide is the Correct Answer:** In **Potassium ferrocyanide ($K_4[Fe(CN)_6]$)**, the cyanide groups are covalently bonded to the central iron atom within a stable complex ion. This bond is so strong that the compound does not dissociate to release free cyanide ions in the human body. Because the CN⁻ ion is not liberated, the compound is physiologically inert and considered **non-poisonous**. It is even used as an anti-caking agent in table salt. **Analysis of Incorrect Options:** * **Potassium Cyanide (KCN) & Sodium Cyanide (NaCN):** These are soluble salts that readily dissociate in the stomach's acidic environment to release hydrogen cyanide gas. They are highly lethal even in small doses (Fatal dose: ~200–300 mg). * **Hydrocyanic Acid (HCN):** Also known as Prussic acid, this is the most toxic form of cyanide. It is a volatile liquid/gas that acts almost instantaneously by inhibiting cellular respiration. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Inhibition of Cytochrome Oxidase $\rightarrow$ Histotoxic Hypoxia. * **Odor:** Characteristically described as **"Bitter Almonds"** (genetically determined ability to smell). * **Post-mortem finding:** **Cherry-red** discoloration of blood, skin, and viscera (due to high oxyhemoglobin levels as tissues cannot utilize oxygen). * **Antidote:** The standard "Cyanide Antidote Kit" includes Amyl nitrite, Sodium nitrite, and Sodium thiosulfate. **Hydroxocobalamin** (Cyanokit) is now the preferred first-line agent.

Q: Purple lining over gums is seen in which chronic poisoning?

Copper. **Explanation:** The correct answer is **Copper**. In chronic copper poisoning (Chalcosis), a characteristic **purple or greenish-purple line** is observed on the gums at the base of the teeth. This occurs due to the deposition of copper salts in the gingival tissues. **Analysis of Options:** * **Copper (Correct):** Chronic exposure leads to a purple/greenish line on the gums. Other features include "Green hair" in copper workers and Wilson’s disease-like symptoms. * **Lead (Incorrect):** Chronic lead poisoning (Plumbism) produces a **Burtonian line**, which is a **bluish-black** punctate line on the gums. It is caused by the reaction of lead with hydrogen sulfide produced by oral bacteria. * **Mercury (Incorrect):** Chronic mercury poisoning (Hydrargyrism) causes a **pinkish-red** discoloration of the gums, often associated with metallic taste, tremors, and "erethism." * **Magnesium (Incorrect):** Magnesium poisoning does not typically manifest with specific gingival pigmentation; it primarily affects neuromuscular and cardiovascular systems (hypermagnesemia). **High-Yield Clinical Pearls for NEET-PG:** * **Burtonian Line:** Lead (Bluish-black) * **Purple/Green Line:** Copper * **Pink/Red Gums:** Mercury * **Yellow/Brown Line:** Cadmium * **Blue-grey Line:** Silver (Argyria) * **Black Line:** Bismuth or Manganese **Note:** These lines are usually absent in edentulous (toothless) patients as they require the presence of dental hygiene-related bacteria to form sulfide precipitates.

Q: The location where strychnine mainly acts for its clinical presentation is:

Anterior horn cells. **Explanation:** **Mechanism of Action (Why B is Correct):** Strychnine is a potent spinal poison derived from the seeds of *Strychnos nux-vomica*. Its primary mechanism involves the **competitive inhibition of Glycine**, which is the major inhibitory neurotransmitter in the spinal cord. Specifically, it acts on the **Anterior Horn Cells (AHCs)** of the spinal cord. By blocking glycine, strychnine removes the "inhibitory break" on motor neurons, leading to uncontrolled, synchronous discharge of the motor neurons. This results in violent, involuntary muscle spasms and convulsions characteristic of strychnine poisoning. **Analysis of Incorrect Options:** * **A. Heart:** While severe spasms can lead to hypoxia and secondary cardiac arrest, strychnine does not have a primary or direct toxicological site of action on the cardiac myocytes. * **C. Posterior Horn Cells:** The posterior horn cells are primarily involved in sensory processing. Strychnine specifically targets the motor outflow pathways (Anterior Horn), which explains the motor-dominant symptoms (convulsions) rather than sensory disturbances. **High-Yield Clinical Pearls for NEET-PG:** * **Opisthotonus:** A characteristic backward arching of the back due to the predominance of powerful extensor muscles. * **Risus Sardonicus:** A fixed, "sardonic" grin caused by spasms of the facial muscles. * **Mind remains clear:** Unlike epilepsy, the patient remains fully conscious and in extreme pain until death, as the cerebral cortex is not primarily affected. * **Post-mortem finding:** Rigor mortis sets in very early and disappears quickly due to the exhaustion of ATP from intense muscular activity. * **Differential Diagnosis:** Often confused with **Tetanus**. (Key difference: In strychnine poisoning, muscles relax completely between convulsions; in tetanus, they do not).

Q: Delayed onset polyneuropathy after Organophosphorous poisoning is typically seen after what time interval?

2-4 weeks. **Explanation:** Organophosphorus (OP) poisoning presents with three distinct neurological phases. The correct answer, **2-4 weeks**, refers to the third phase, known as **Organophosphate-Induced Delayed Polyneuropathy (OPIDP).** **1. Why 2-4 weeks is correct:** OPIDP is a symmetrical, sensory-motor axonopathy. It is caused by the inhibition of **Neuropathy Target Esterase (NTE)**, rather than acetylcholinesterase. This inhibition leads to axonal degeneration (Wallerian-type) of long peripheral nerves and spinal cord tracts. Clinically, it presents 2 to 4 weeks after the acute crisis as "burning" paresthesia followed by motor weakness, typically starting in the distal lower limbs (foot drop). **2. Why other options are incorrect:** * **1-2 weeks:** This is too early for OPIDP. However, the **Intermediate Syndrome (Type II paralysis)** typically occurs 24–96 hours after exposure, affecting proximal muscles and cranial nerves. * **4-6 weeks and 6-8 weeks:** While symptoms may persist during this time, the *onset* of the neuropathy is characteristically established within the 14–28 day window. **High-Yield Clinical Pearls for NEET-PG:** * **The Three Phases of OP Poisoning:** 1. **Acute Cholinergic Crisis:** Minutes to hours (SLUDGE/DUMBELS symptoms). 2. **Intermediate Syndrome:** 1–4 days (Proximal muscle weakness; "Neck flexor" weakness is a hallmark). 3. **OPIDP:** 2–4 weeks (Distal degeneration; NTE inhibition). * **Common Culprits for OPIDP:** Triorthocresyl phosphate (TOCP), Leptophos, and Mipafox. * **Treatment Note:** Atropine and Oximes are effective for the acute phase but have **no role** in preventing or treating OPIDP. Management is primarily supportive and rehabilitative.

Q: Opium is derived from which part of the plant?

Unripe capsule. **Explanation:** Opium is an alkaloid-rich substance obtained from the plant **Papaver somniferum**. The correct answer is the **unripe capsule** because opium is harvested by a process called **incising (lancing)**. When the green, unripe seed pod (capsule) is shallowly cut, a milky white latex exudes. This latex air-dries into a brown, sticky gum, which is then scraped off to produce raw opium. **Analysis of Options:** * **A. Leaf:** The leaves of the poppy plant do not contain sufficient concentrations of alkaloids (like morphine or codeine) to be used for opium production. * **B. Root:** While the plant roots contain trace elements, they are not a source of the narcotic latex. * **C. Poppy seed:** Also known as *Khas-Khas*, these are found inside the capsule. They are **non-narcotic**, contain no opium, and are commonly used in culinary preparations. However, they may be contaminated with morphine residue on the surface during harvesting. * **D. Unripe capsule (Correct):** Specifically, the "incised" unripe capsule is the only anatomical source of the commercial latex. **High-Yield Clinical Pearls for NEET-PG:** * **Alkaloids:** Opium contains Phenanthrene derivatives (Morphine, Codeine, Thebaine) and Isoquinoline derivatives (Papaverine, Noscapine). * **The "Somniferum" name:** Derived from Latin, meaning "sleep-bringing." * **Poppy Straw:** Refers to the dried capsule after the seeds are removed; it still contains small amounts of alkaloids. * **Clinical Triad of Opioid Poisoning:** Pinpoint pupil (miosis), respiratory depression, and coma. * **Antidote:** Naloxone (competitive opioid antagonist).

Q: Which of the following substances is commonly known as "Angel Dust"?

Phencyclidine. **Explanation:** **Phencyclidine (PCP)** is a dissociative anesthetic originally developed for medical use but discontinued due to severe adverse effects. It is street-named **"Angel Dust"** because of its white crystalline powder form and its potent psychoactive effects. Pharmacologically, it acts as an **NMDA receptor antagonist**, leading to a state of "dissociative anesthesia" where the patient feels detached from their environment and pain. **Analysis of Options:** * **LSD (Lysergic Acid Diethylamide):** Known as "Acid." It is a potent hallucinogen acting primarily on serotonin receptors. It is famous for causing "trips" and "flashbacks." * **Heroin:** A semi-synthetic opioid derived from morphine, commonly known as "Smack," "Horse," or "Brown Sugar." It causes CNS depression and pinpoint pupils. * **Charas:** A resinous extract from *Cannabis sativa*, often called "Hashish." It is a cannabinoid, not a dissociative anesthetic. **High-Yield Clinical Pearls for NEET-PG:** 1. **Vertical Nystagmus:** This is a classic, pathognomonic sign of PCP toxicity (most other drugs cause horizontal nystagmus). 2. **Agitated Delirium:** PCP users often exhibit "superhuman strength," extreme aggression, and a high tolerance to pain, making them difficult to restrain. 3. **Mechanism:** Like Ketamine, PCP blocks NMDA receptors but is significantly more toxic and prone to causing psychosis. 4. **Management:** Avoid phenothiazines (can lower seizure threshold); use Benzodiazepines for sedation and maintain a quiet environment.

Q: What is ophitoxemia?

Snakebite poisoning. **Explanation:** **Ophitoxemia** is the medical term used to describe **snakebite poisoning** or envenomation. The term is derived from the Greek word *"Ophis"* (meaning snake) and *"Toxemia"* (meaning blood poisoning). It refers to the systemic clinical condition resulting from the inoculation of venom into the body through a snake's fangs. **Analysis of Options:** * **Option A (Correct):** Ophitoxemia specifically refers to the toxic state induced by snake venom. In forensic medicine, snakebites are classified as "animal irritant poisons." * **Option B (Incorrect):** Phenol poisoning (Carbolic acid) is known as **Carbolism**. It is characterized by "ochronosis" (pigmentation of cartilage) and "carboluria" (greenish-black urine). * **Option C (Incorrect):** Chronic lead poisoning is termed **Plumbism** or **Saturnism**. Key features include Burtonian lines on gums, basophilic stippling of RBCs, and wrist drop. * **Option D (Incorrect):** Opium poisoning is a somniferous (hypnotic) poison. Chronic abuse is often associated with the term "Opium eating" or "Morphinism." **High-Yield Clinical Pearls for NEET-PG:** 1. **Classification:** Snake venom is a complex mixture of enzymes (like Phospholipase A2 and Hyaluronidase). 2. **Elapidae (Cobra, Krait):** Primarily **neurotoxic**, causing flaccid paralysis and respiratory failure. 3. **Viperidae (Vipers):** Primarily **vasculotoxic**, causing local edema, cellulitis, and coagulation defects (DIC). 4. **Hydrophidae (Sea Snakes):** Primarily **myotoxic**, leading to rhabdomyolysis and myoglobinuria. 5. **Diagnosis:** The **20-minute Whole Blood Clotting Test (20WBCT)** is the most reliable bedside test to detect coagulopathy in viper bites.

Q: Which poisoning is also known as St. Anthony's fire?

Ergot poisoning. **Explanation:** **Ergot poisoning (Ergotism)** is caused by the ingestion of alkaloids produced by the fungus *Claviceps purpurea*, which infects rye and other cereal grains. The term **"St. Anthony’s Fire"** refers specifically to the **gangrenous form** of ergotism. The alkaloids (like ergotamine) cause potent, prolonged vasoconstriction of peripheral arteries, leading to a burning sensation in the limbs, followed by dry gangrene and eventual auto-amputation. It was named after monks of the Order of St. Anthony who treated victims during the Middle Ages. **Analysis of Incorrect Options:** * **Heroin poisoning:** Presents with the classic triad of miosis (pinpoint pupils), respiratory depression, and coma. It does not cause peripheral gangrene. * **Mushroom poisoning:** Most commonly associated with *Amanita phalloides* (Death Cap), leading to fulminant hepatic failure and gastroenteritis, not chronic vasoconstrictive symptoms. * **Dhatura poisoning:** Known as "Road Poison," it presents with anticholinergic symptoms (the "5 D’s": Dryness of mouth, Dysphagia, Dilated pupils, Delirium, and Death). **High-Yield Clinical Pearls for NEET-PG:** * **Two types of Ergotism:** 1. **Gangrenous** (St. Anthony's Fire) and 2. **Convulsive** (presents with tingling, numbness, and painful seizures). * **LSD Connection:** Lysergic acid diethylamide (LSD) is a semisynthetic derivative of ergot alkaloids. * **Diagnostic Sign:** Ergotism can mimic Buerger’s disease or Raynaud’s phenomenon due to its intense vasoconstrictive properties. * **Treatment:** Vasodilators (like Sodium Nitroprusside) and anticoagulants are used to manage the ischemia.

Question 1

A patient ingested an unknown substance and presented with myoclonic jerks, seizures, tachycardia, and hypotension. ECG shows a heart rate of 120/min. Arterial blood revealed a pH of 7.25, pCO2 of 30 mm Hg, and bicarbonate ions of 15 mmol/L. What is the most likely poisonous agent?

Accepted Answer

Imipramine

Answer

Amanita phalloides

Answer

Ethylene glycol

Answer

Phencyclidine

Question 2

Which of the following salts of cyanide is considered non-poisonous?

Accepted Answer

Potassium ferrocyanide

Answer

Potassium cyanide

Answer

Hydrocyanic acid

Answer

Sodium cyanide

Question 3

Purple lining over gums is seen in which chronic poisoning?

Accepted Answer

Copper

Answer

Magnesium

Answer

Lead

Answer

Mercury

Question 4

The location where strychnine mainly acts for its clinical presentation is:

Accepted Answer

Anterior horn cells

Answer

Heart

Answer

Posterior horn cells

Answer

All of the above

Question 5

Delayed onset polyneuropathy after Organophosphorous poisoning is typically seen after what time interval?

Accepted Answer

2-4 weeks

Answer

1-2 weeks

Answer

4-6 weeks

Answer

6-8 weeks

Question 6

Opium is derived from which part of the plant?

Accepted Answer

Unripe capsule

Answer

Leaf

Answer

Root

Answer

Poppy seed

Question 7

Which of the following substances is commonly known as "Angel Dust"?

Accepted Answer

Phencyclidine

Answer

LSD

Answer

Heroin

Answer

Charas

Question 8

All of the following are indications for medical termination of pregnancy except?

Accepted Answer

Very poor socioeconomic position of the family

Answer

Pregnancy resulting from rape

Answer

Substantial risk of delivering a seriously handicapped baby

Answer

Injury to the physical and mental health of the pregnant woman

Question 9

What is ophitoxemia?

Accepted Answer

Snakebite poisoning

Answer

Phenol poisoning

Answer

Chronic lead poisoning

Answer

Opium poisoning

Question 10

Which poisoning is also known as St. Anthony's fire?

Accepted Answer

Ergot poisoning

Answer

Heroin poisoning

Answer

Mushroom poisoning

Answer

Dhatura poisoning

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

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