Forensic Toxicology Practice Questions

Q: Ethylene glycol when ingested affects the kidney by forming which of the following?

Oxalates. **Explanation:** Ethylene glycol (commonly found in antifreeze) is a toxic alcohol that undergoes a specific metabolic pathway in the liver. The correct answer is **Oxalates** because of the following biochemical sequence: 1. **Metabolism:** Ethylene glycol is metabolized by *Alcohol Dehydrogenase* into glycoaldehyde, then to glycolic acid, and finally to **oxalic acid**. 2. **Mechanism of Renal Injury:** Oxalic acid combines with calcium to form **Calcium Oxalate crystals**. These needle-shaped (monohydrate) or envelope-shaped (dihydrate) crystals precipitate within the renal tubules, leading to mechanical obstruction, acute tubular necrosis (ATN), and acute kidney injury. **Analysis of Incorrect Options:** * **A. Formaldehyde:** This is a metabolite of **Methanol**, not ethylene glycol. Methanol metabolism leads to formaldehyde and then formic acid, which causes retinal toxicity and metabolic acidosis. * **C & D. Phytates and Phosphates:** These are not metabolites of ethylene glycol. While phosphates are involved in various metabolic processes, they do not play a primary role in the specific pathophysiology of ethylene glycol poisoning. **Clinical Pearls for NEET-PG:** * **Classic Triad:** High anion gap metabolic acidosis (HAGMA), high osmolar gap, and **calcium oxalate crystalluria**. * **Antidote:** **Fomepizole** (inhibits alcohol dehydrogenase) is the preferred treatment. Ethanol can be used as an alternative. * **Microscopy:** Look for "envelope-shaped" crystals in the urine sediment. * **Fluorescence:** Urine may fluoresce under a Wood’s lamp if the ingested antifreeze contained fluorescein.

Q: What percentage of carboxyhemoglobin (COHb) can cause death?

82%. **Explanation:** Carbon monoxide (CO) has an affinity for hemoglobin that is 200–300 times greater than oxygen, forming **Carboxyhemoglobin (COHb)**. This shifts the oxygen-dissociation curve to the left, leading to cellular hypoxia. 1. **Why 82% is Correct:** In forensic toxicology and pathology (Reddy’s *The Essentials of Forensic Medicine and Toxicology*), it is established that while symptoms begin at lower levels, a COHb concentration of **80% or more** is generally considered fatal. Specifically, **82%** is cited in standard textbooks as the threshold where death is inevitable due to total respiratory failure and systemic anoxia. 2. **Analysis of Incorrect Options:** * **70% & 75%:** At these levels (60–75%), a person will experience severe confusion, seizures, and coma. While potentially fatal if exposure continues, they are often considered the "critical" range rather than the definitive lethal threshold used in forensic examinations. * **80%:** While 80% is the general benchmark for fatality, in a multiple-choice format where 82% is provided, 82% is the more precise "textbook" value indicating the upper limit of saturation found in post-mortem cases. **High-Yield Clinical Pearls for NEET-PG:** * **Cherry Red Discoloration:** The most characteristic post-mortem finding of CO poisoning (seen in skin, mucous membranes, and blood). * **CT/MRI Finding:** Bilateral necrosis of the **Globus Pallidus** is a classic sign of CO poisoning. * **Treatment:** 100% Oxygen (reduces half-life of COHb from 5 hours to 80 minutes) or Hyperbaric Oxygen. * **Rule of Thumb:** 30% COHb = Severe headache/dizziness; 50% = Confusion/Syncope; >80% = Death.

Q: Which of the following chemical burns is most likely to lead to hypoglycemia?

Hydrofluoric acid. **Explanation:** **Hydrofluoric Acid (HF)** is unique among chemical burns because it causes systemic toxicity far beyond local tissue destruction. The fluoride ion is highly electronegative and penetrates deeply into tissues, where it binds to divalent cations. 1. **Mechanism of Hypoglycemia:** While HF is most famous for causing life-threatening **hypocalcemia** and **hypomagnesemia**, it also interferes with cellular metabolism. Systemic fluoride toxicity inhibits various enzyme systems, including those involved in glycolysis and gluconeogenesis. Specifically, it can lead to a profound metabolic derangement that manifests as **hypoglycemia**, alongside hyperkalemia and cardiac arrhythmias (QT prolongation). **Why other options are incorrect:** * **Sulfuric Acid (A) and Nitric Acid (C):** These are strong mineral acids that cause **coagulative necrosis**. Their primary effect is local tissue destruction (charring with sulfuric acid; yellow discoloration/xanthoproteic reaction with nitric acid). They do not typically cause systemic metabolic disturbances like hypoglycemia. * **Acetic Acid (D):** This is an organic acid. While concentrated forms can cause burns and hemolysis if ingested, it does not have a specific mechanism linked to systemic hypoglycemia. **High-Yield Clinical Pearls for NEET-PG:** * **HF Burn Hallmark:** "Pain out of proportion to physical findings." * **Antidote:** **Calcium Gluconate** (topical gel, intra-arterial, or intravenous) to neutralize the fluoride ion. * **Electrolyte Triad of HF:** Hypocalcemia, Hypomagnesemia, and Hyperkalemia. * **Nitric Acid:** Causes **Xanthoproteic reaction** (yellow staining of skin/tissues). * **Sulfuric Acid:** Known as "Oil of Vitriol"; causes blackening of the skin.

Q: Rectified spirit cannot be used as a preservative in all except which of the following?

Plant alkaloids. **Explanation:** In forensic toxicology, the preservation of viscera is crucial for accurate chemical analysis. **Saturated Saline** is the routine preservative of choice for most poisons. However, **Rectified Spirit (95% Ethyl Alcohol)** is specifically used as a preservative when certain poisons are suspected, as it prevents their degradation without interfering with the chemical analysis. **Why Plant Alkaloids is the Correct Answer:** Rectified spirit is the **preservative of choice** for cases of suspected poisoning by **plant alkaloids** (e.g., Strychnine, Dhatura, Aconite, Opium). Alkaloids are highly soluble in alcohol, which facilitates their extraction and stabilization during toxicological analysis. **Why the Other Options are Incorrect:** Rectified spirit **cannot** be used in the following cases because it interferes with the detection of the poison: * **Alcohol (Option C):** If alcohol is suspected as the cause of death, using rectified spirit (which is itself alcohol) would make it impossible to determine the concentration of alcohol consumed by the deceased. * **Kerosene (Option A):** Rectified spirit is a hydrocarbon solvent and would mask or interfere with the identification of other volatile hydrocarbons like kerosene or petrol. * **Phosphorus (Option D):** Rectified spirit reacts with phosphorus, potentially leading to its oxidation or dissolution, thereby hindering detection. Saturated saline is preferred here. **High-Yield NEET-PG Pearls:** * **Preservative of Choice (General):** Saturated Saline. * **Preservative for Alcohol/Kerosene/Phosphorus:** Saturated Saline. * **Preservative for Plant Alkaloids:** Rectified Spirit. * **Preservative for Blood (Toxicology):** Sodium fluoride (10 mg/ml) is added as a preservative and anticoagulant (it inhibits glycolysis and bacterial growth). * **Preservative for Urine:** Thymol or Phenylmercuric nitrate.

Q: Who is considered the father of toxicology?

Orfila. **Explanation:** **Mathieu Orfila (Option D)** is recognized as the **Father of Modern Toxicology**. A Spanish-born French physician, he published *Traité des poisons* in 1814, which was the first systematic approach to the study of poisons. He was the first to use chemical analysis to detect poisons in body tissues (specifically arsenic) and played a pivotal role in the famous Marie Lafarge case, marking the birth of forensic toxicology as a scientific discipline. **Analysis of Incorrect Options:** * **Paracelsus (Option A):** Often called the **"Father of Toxicology"** (in a general sense), he famously stated, *"The dose makes the poison."* While he laid the philosophical foundation, Orfila is specifically credited with the scientific and forensic application. * **Galen (Option B):** A Greek physician whose work dominated Western medical science for centuries; he focused on anatomy and physiology, not toxicology. * **Galton (Option C):** Sir Francis Galton is known for his work in eugenics and **fingerprinting** (Galton’s details/minutiae), not toxicology. **High-Yield Clinical Pearls for NEET-PG:** * **Father of Modern Toxicology:** Mathieu Orfila. * **Father of Indian Toxicology:** Dr. V.V. Pillay (author of the standard Indian textbook). * **The "Ideal Poison":** Thallium (tasteless, odorless, mimics natural illness). * **Marsh Test:** The first chemical test used by Orfila to detect arsenic in human tissue. * **Antidote of Choice for Unknown Poisoning:** Universal Antidote (Activated charcoal, Magnesium oxide, and Tannic acid).

Q: Oduvanthalai poisoning is associated with which of the following?

Hypokalemia. **Explanation:** **Oduvanthalai** (*Cleistanthus collinus*) is a highly toxic plant common in South India, frequently used for suicidal purposes. The primary toxins involved are **cleistanthin A and B** (glycosides) and **diphyllin**. 1. **Why Hypokalemia is Correct:** The toxins in Oduvanthalai act as potent inhibitors of the **vacuolar-type H+-ATPase pump** and the **Na+-K+ ATPase pump** in the distal renal tubules. This leads to **Distal Renal Tubular Acidosis (Type 1 RTA)**. The inhibition of these pumps results in significant urinary loss of potassium, leading to profound **hypokalemia**. This electrolyte imbalance is the hallmark of the poisoning and is the primary cause of life-threatening cardiac arrhythmias and neuromuscular paralysis. 2. **Analysis of Incorrect Options:** * **Hyponatremia:** While electrolyte shifts occur, sodium levels are typically normal or less significantly affected compared to the dramatic drop in potassium. * **Respiratory Acidosis:** The poisoning causes **Metabolic Acidosis** (due to RTA), not respiratory. Respiratory failure may occur terminally, but the primary acid-base disturbance is metabolic. * **Metabolic Alkalosis:** This is incorrect because the renal tubular damage prevents the excretion of hydrogen ions, leading to a state of systemic acidosis. **Clinical Pearls for NEET-PG:** * **Target Organ:** Primarily affects the Kidneys (RTA), Heart (Arrhythmias), and Lungs (ARDS). * **ECG Findings:** Look for signs of hypokalemia (U-waves, T-wave flattening, ST-depression). * **Management:** There is no specific antidote. Treatment is supportive, focusing on **aggressive potassium correction** and correcting metabolic acidosis. * **High-Yield Association:** *Cleistanthus collinus* = Hypokalemia + Metabolic Acidosis + Distal RTA.

Q: An industrial worker presents with blue lines on the gums. What is the most probable cause?

Lead poisoning. The presence of blue-black lines on the gums, known as **Burtonian lines**, is a classic clinical sign of chronic **Lead poisoning (Plumbism)**. ### **Explanation of the Correct Answer** The Burtonian line occurs due to the reaction between circulating lead and sulfur-producing bacteria in the mouth. Lead reacts with hydrogen sulfide (produced by food debris/bacteria) to form **Lead Sulfide (PbS)**, which precipitates as a bluish-purple line along the gingival margin. This is most commonly seen in patients with poor oral hygiene. ### **Analysis of Incorrect Options** * **Arsenic poisoning:** Chronic arsenicosis is characterized by "Raindrop pigmentation" of the skin, hyperkeratosis of palms/soles, and **Mees' lines** (white transverse bands on nails), but not gingival lines. * **Mercury poisoning:** Chronic mercury poisoning (Hydrargyrism) presents with **Erethism** (behavioral changes), **Mercurialentis** (brown reflex in the eye), and tremors (Danbury tremor). While it can cause gingivitis and loose teeth, the specific "blue line" is characteristic of lead. * **Copper poisoning:** Acute copper toxicity leads to a metallic taste and blue-green vomitus/diarrhea. Chronic exposure (Wilson’s disease) presents with **Kayser-Fleischer (KF) rings** in the cornea, not gum lines. ### **NEET-PG High-Yield Pearls** * **Lead Poisoning Triad:** Abdominal colic, Anemia (with **Basophilic stippling**), and Wrist drop/Foot drop. * **Radiology:** "Lead lines" (increased density) at the metaphysis of long bones in children. * **Treatment:** DOC for Lead Encephalopathy is **BAL + EDTA**; for mild cases, **Succimer (DMSA)** is preferred. * **Other Gum Lines:** Bismuth poisoning can also cause a similar dark line, but Lead is the most common cause tested in industrial contexts.

Q: Hematuria is a feature of snake bite due to which of the following?

Viper. **Explanation:** The correct answer is **Viper**. Snake bites are broadly classified based on their toxin's primary target: neurotoxic, vasculotoxic (hematotoxic), or myotoxic. **1. Why Viper is correct:** Vipers (such as the Russell’s Viper and Saw-scaled Viper) possess **vasculotoxic** venom. This venom contains procoagulants (like factor X and prothrombin activators), hemorrhagins, and phospholipase A2. These toxins disrupt the vascular endothelium and trigger a consumption coagulopathy (DIC-like syndrome). This leads to systemic bleeding manifestations, of which **hematuria** (blood in urine) is a hallmark clinical sign, along with bleeding from gums, epistaxis, and hemoptysis. **2. Why the other options are incorrect:** * **Cobra & Krait (Options A & B):** These are **Elapids**, which are primarily **neurotoxic**. Their venom acts on the neuromuscular junction (Cobra: post-synaptic; Krait: pre-synaptic), leading to muscle paralysis, ptosis, and respiratory failure. They do not typically cause bleeding or hematuria. * **Sea Snake (Option D):** Sea snake venom is primarily **myotoxic**. It causes generalized muscle aches and rhabdomyolysis. While this leads to **myoglobinuria** (which can make urine look dark), it is not true hematuria (intact RBCs in urine). **Clinical Pearls for NEET-PG:** * **Viper:** Causes "Viperine sign" (local swelling) and **renal failure** (acute tubular necrosis). * **Krait:** Known for "Nocturnal bites" and "Silent abdomen" (due to paralytic ileus). * **Cobra:** Causes local tissue necrosis/sloughing at the bite site. * **Test of choice:** The **20-minute Whole Blood Clotting Test (20WBCT)** is the bedside gold standard to diagnose vasculotoxic (Viper) bites.

Question 1

Ethylene glycol when ingested affects the kidney by forming which of the following?

Accepted Answer

Oxalates

Answer

Formaldehyde

Answer

Phytates

Answer

Phosphates

Question 2

What percentage of carboxyhemoglobin (COHb) can cause death?

Accepted Answer

82%

Answer

70%

Answer

75%

Answer

80%

Question 3

Which of the following chemical burns is most likely to lead to hypoglycemia?

Accepted Answer

Hydrofluoric acid

Answer

Sulfuric acid

Answer

Nitric acid

Answer

Acetic acid

Question 4

Rectified spirit cannot be used as a preservative in all except which of the following?

Accepted Answer

Plant alkaloids

Answer

Kerosene

Answer

Alcohol

Answer

Phosphorus

Question 5

Which of the following is true in relation to Ethylene glycol poisoning?

Accepted Answer

It may present with an acute ascending motor and sensory neuropathy.

Answer

A normal anion gap acidosis is usually seen.

Answer

Alcohol dehydrogenase metabolizes Ethylene glycol into metabolites including oxalate and glycolic acid.

Answer

Hemodialysis is not effective.

Question 6

Who is considered the father of toxicology?

Accepted Answer

Orfila

Answer

Paracelsus

Answer

Galen

Answer

Galton

Question 7

Which of the following order is true about the toxicity of mercury compounds?

Accepted Answer

Organic salts > mercuric salts > mercurous salts

Answer

Mercuric salts > organic salts > mercurous salts

Answer

Mercuric salts > mercurous salts > organic salts

Answer

Mercurous salts > organic salts > mercuric salts

Question 8

Oduvanthalai poisoning is associated with which of the following?

Accepted Answer

Hypokalemia

Answer

Hyponatremia

Answer

Respiratory acidosis

Answer

Metabolic alkalosis

Question 9

An industrial worker presents with blue lines on the gums. What is the most probable cause?

Accepted Answer

Lead poisoning

Answer

Arsenic poisoning

Answer

Mercury poisoning

Answer

Copper poisoning

Question 10

Hematuria is a feature of snake bite due to which of the following?

Accepted Answer

Viper

Answer

Cobra

Answer

Krait

Answer

Sea snake

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

On this page

Practice by Chapter

Want unlimited practice?