Forensic Toxicology Practice Questions

Q: All of the following are combinations of poisoning and their specific antidote except?

Mercury salts-Dimercaprol. This question tests the knowledge of specific antidotes and chelating agents in toxicology. The correct answer is **B (Mercury salts-Dimercaprol)** because, while Dimercaprol (BAL) is used for some forms of mercury, it is specifically **contraindicated** in cases of poisoning by elemental or methyl mercury (organic mercury) as it can increase the distribution of mercury to the brain. For inorganic mercury salts, **DMSA (Succimer)** is now the preferred agent. ### Explanation of Options: * **A. Morphine-Naloxone:** This is a correct pairing. Naloxone is a pure opioid antagonist that competitively binds to mu-receptors, reversing respiratory depression in opioid toxicity. * **C. Organophosphorous (OP) insecticide-Atropine:** This is a correct pairing. Atropine is the specific physiological antidote that antagonizes the muscarinic effects of accumulated acetylcholine. (Note: Pralidoxime is the specific biochemical antidote/oxime). * **D. Copper salts-Penicillamine:** This is a correct pairing. D-Penicillamine is the primary chelating agent used for copper toxicity and Wilson’s disease. ### High-Yield Clinical Pearls for NEET-PG: * **BAL (Dimercaprol):** Used for Arsenic, Mercury (inorganic), and Lead (along with EDTA). It is oily, given IM, and contains sulfur (contraindicated in peanut allergy). * **DMSA (Succimer):** The "Water-soluble BAL." It is the drug of choice for Lead poisoning in children and is preferred for Mercury and Arsenic. * **Iron Poisoning:** Deferoxamine (look for "vin-rose" colored urine). * **Methanol:** Fomepizole (inhibits alcohol dehydrogenase) or Ethanol. * **Benzodiazepines:** Flumazenil. * **Acetaminophen:** N-acetylcysteine (replenishes glutathione).

Q: Gastric lavage turns black in the presence of silver nitrate. What is the most probable poisoning?

Celphos. **Explanation:** The correct answer is **Celphos (Aluminium Phosphide)**. **1. Why Celphos is correct:** Celphos is the brand name for Aluminium Phosphide. When it comes into contact with moisture or gastric acid (HCl), it releases **Phosphine gas ($PH_3$)**. The diagnostic bedside test for phosphine involves using **Silver Nitrate ($AgNO_3$)**. When phosphine gas reacts with silver nitrate, it reduces the silver ions to metallic silver, resulting in a **black discoloration**. * **Reaction:** $PH_3 + 3AgNO_3 \rightarrow Ag_3P$ (Silver phosphide) + $3HNO_3$. The silver phosphide then reacts further to form black metallic silver. * This test can be performed on gastric aspirate or by placing a silver nitrate-soaked filter paper over the mouth of the patient (the paper turns black if phosphine is exhaled). **2. Why other options are incorrect:** * **Malathion, Organophosphorus, and Parathion:** These are all Organophosphate (OP) compounds. While they are common causes of poisoning, they do not react with silver nitrate to produce a black color. OP poisoning is clinically diagnosed by the "cholinergic sludge" (miosis, salivation, lacrimation) and a characteristic **garlic-like odor** of the breath/vomitus, but the silver nitrate test is specific for phosphides. **3. Clinical Pearls for NEET-PG:** * **Odor:** Celphos poisoning is characterized by a **garlic or decayed fish odor**. * **Mechanism:** Phosphine is a potent mitochondrial toxin that inhibits **Cytochrome C oxidase**, leading to cellular hypoxia and multi-organ failure. * **Management:** There is no specific antidote. Treatment is supportive, often involving gastric lavage with **Potassium Permanganate ($KMnO_4$)** (1:10,000) to oxidize phosphine to non-toxic phosphate. * **Radiology:** "Garlic breath" + "Shock" + "Positive Silver Nitrate test" = Aluminium Phosphide.

Q: Symptoms of opium poisoning are all EXCEPT:

Diarrhea. **Explanation:** Opium poisoning (Opioid toxicity) typically presents with a classic triad of **miosis (pinpoint pupils), respiratory depression, and a depressed level of consciousness.** **Why Diarrhea is the Correct Answer:** Opioids act on the mu-opioid receptors in the gastrointestinal tract to **decrease motility** and increase sphincter tone. This leads to **constipation**, not diarrhea. In fact, opioids are therapeutically used as anti-diarrheal agents (e.g., Loperamide). Diarrhea is a hallmark symptom of opioid *withdrawal*, rather than acute poisoning. **Analysis of Incorrect Options:** * **Respiratory Depression (A):** This is the most dangerous complication and the most common cause of death in opioid overdose. Opioids decrease the brainstem's sensitivity to carbon dioxide. * **Orthostatic Hypotension (B):** Opioids cause peripheral vasodilation (partly due to histamine release) and blunt the baroreceptor reflex, leading to a drop in blood pressure upon standing. * **Seizures (D):** While opioids are generally CNS depressants, certain opioids (like Tramadol, Meperidine/Pethidine) or severe hypoxia resulting from respiratory depression can trigger seizures. **High-Yield Clinical Pearls for NEET-PG:** * **The Opioid Triad:** Coma, Pinpoint pupils, and Respiratory depression. * **Exception to Miosis:** Pethidine (Meperidine) poisoning causes **mydriasis** (dilated pupils) due to its atropine-like action. * **Specific Antidote:** **Naloxone** (pure opioid antagonist). It has a shorter half-life than most opioids, so repeated dosing or infusion may be required to prevent "re-narcotization." * **Post-mortem finding:** "Froth at the mouth and nostrils" is a common finding due to pulmonary edema.

Q: In sulfuric acid poisoning, all the following are seen, except?

Swollen tongue with white coating. **Explanation:** Sulfuric acid ($H_2SO_4$) is a powerful **corrosive mineral acid** that acts by intense dehydration and heat generation (exothermic reaction), leading to **liquefactive necrosis** and charring of tissues. **Why Option D is the Correct Answer:** In sulfuric acid poisoning, the tongue is typically **shrunken, charred, and blackened** due to the acid's dehydrating effect and the formation of acid-hematin. A "swollen tongue with a white coating" is characteristic of **mercury poisoning** or certain milder irritants, not a strong dehydrating acid like sulfuric acid. **Analysis of Incorrect Options:** * **A. Dryness of mouth:** Sulfuric acid is extremely hygroscopic. It withdraws water from the tissues instantly, leading to profound dryness and parchment-like skin/mucosa. * **B. Damaged tongue:** The corrosive action causes immediate chemical burns, sloughing, and destruction of the lingual mucosa. * **C. Chalky white teeth:** This is a **classic high-yield sign** of sulfuric acid ingestion. The acid reacts with the calcium in the tooth enamel, causing it to lose its luster and appear dull, opaque, or "chalky white." **Clinical Pearls for NEET-PG:** * **Vitriolage:** The act of throwing sulfuric acid (Oil of Vitriol) on a person. * **Stomach Appearance:** The stomach in sulfuric acid poisoning shows "coffee-ground" vomitus and a blackened, charred wall (perforation is common). * **Magnesium Silicate (Talcs):** Used as an antidote to neutralize the acid. * **Mnemonic:** Sulfuric acid = **S**hrunken/Blackened; Nitric acid = **Y**ellow (Xanthoproteic reaction); Hydrochloric acid = **W**hite/Greyish.

Q: The brain is preserved in all of the following types of poisoning, except:

Heavy metal poisoning. **Explanation:** In medicolegal autopsies, the preservation of specific viscera depends on the metabolic pathway and distribution of the suspected poison. **Why Heavy Metal Poisoning is the Correct Answer:** In cases of **Heavy Metal poisoning** (e.g., Arsenic, Antimony, Mercury), the brain is generally **not** preserved. Instead, the specific tissues required for chemical analysis are the **long bones** (femur), **hair** (plucked with roots), and **nails**. These tissues act as reservoirs where heavy metals accumulate over time. For acute cases, the standard viscera (stomach, intestines, liver, kidney, and spleen) are sufficient. **Analysis of Incorrect Options:** * **Organophosphate Poisoning:** The brain is preserved because it is rich in lipids and can contain significant residues of lipophilic pesticides. It is also useful for testing acetylcholinesterase levels. * **Alkaloid Poisoning:** In deaths due to alkaloids (e.g., Strychnine, Datura, Opium), the brain is a routine requirement for preservation as these substances are neurotropic and can be detected in cerebral tissue. * **Volatile Organic Poisoning:** For volatile poisons (e.g., Alcohol, Chloroform, Kerosene), the brain is the preferred organ for preservation because its high lipid content retains these substances longer than other tissues, and it is less prone to contamination from post-mortem fermentation. **High-Yield Clinical Pearls for NEET-PG:** * **Preservative of Choice:** Saturated Sodium Chloride (Common Salt) is used for most viscera. **Exception:** Rectified spirit is used for most poisons *except* alcohol, acetic acid, and paraldehyde. * **Vitreous Humor:** Highly useful for estimating the time since death (potassium levels) and detecting alcohol or glucose. * **Brain Preservation:** Always prioritize the brain in cases of **anesthetic deaths** and **narcotic poisoning**.

Q: Itai Itai disease is caused by toxicity of:

Cadmium. **Explanation:** **Itai-Itai disease** is a chronic condition caused by long-term **Cadmium (Cd)** poisoning. The term, which translates to "ouch-ouch" disease, was coined in Japan in the 1950s following mass contamination of the Jinzū River. **Why Cadmium is Correct:** Cadmium toxicity primarily affects the proximal renal tubules, leading to severe renal dysfunction (Fanconi-like syndrome). This results in the excessive loss of calcium and phosphate in the urine, leading to **osteomalacia** (softening of bones) and **osteoporosis**. Patients suffer from multiple pathological fractures and intense bone pain, giving the disease its name. **Analysis of Incorrect Options:** * **Antimony:** Toxicity typically presents with gastrointestinal distress, metallic taste, and myocardial depression, but it does not cause bone softening or Itai-Itai disease. * **Lead:** Chronic lead poisoning (Plumbism) is characterized by the "ABCDEF" mnemonic: Anemia (basophilic stippling), Burtonian lines (blue gums), Colic, Dorsiflexion paralysis (wrist/foot drop), Encephalopathy, and Facies (pallor). * **Mercury:** Chronic toxicity causes **Minamata disease** (neurological syndrome), Erethism (abnormal irritability), and Acrodynia (Pink disease). **High-Yield Clinical Pearls for NEET-PG:** * **Source:** Cadmium is found in rechargeable batteries, pigments, and cigarette smoke. * **Diagnosis:** Elevated urinary β2-microglobulin is a sensitive marker for cadmium-induced renal tubular damage. * **Key Triad of Itai-Itai:** Osteomalacia, Renal tubular dysfunction, and severe bone pain. * **Treatment:** Chelation with EDTA may be used, though prevention of exposure is primary.

Question 1

All of the following are combinations of poisoning and their specific antidote except?

Accepted Answer

Mercury salts-Dimercaprol

Answer

Morphine-Naloxone

Answer

Organophosphorous insecticide-atropine

Answer

Copper salts-Penicillamine

Question 2

Gastric lavage turns black in the presence of silver nitrate. What is the most probable poisoning?

Accepted Answer

Celphos

Answer

Malathion

Answer

Organophosphorus

Answer

Parathion

Question 3

A 75-year-old man who lives alone in a poorly ventilated house without central heating uses a portable unvented kerosene heater to warm the house during the winter months. One morning, a neighbor finds him in an obtunded state. On physical examination, he appears cyanotic. Results of blood gas measurement on room air are PO2, 90 mm Hg; PCO2, 35 mm Hg; and pH, 7.3. Pulse oximetry shows low oxygen saturation. Exposure to which of the following is most likely to have produced this man's illness?

Accepted Answer

Carbon monoxide

Answer

Beryllium

Answer

Nitrous oxide compounds

Answer

Oxygen

Question 4

Symptoms of opium poisoning are all EXCEPT:

Accepted Answer

Diarrhea

Answer

Respiratory depression

Answer

Orthostatic hypotension

Answer

Seizures

Question 5

In sulfuric acid poisoning, all the following are seen, except?

Accepted Answer

Swollen tongue with white coating

Answer

Dryness of mouth

Answer

Damaged tongue

Answer

Chalky white teeth

Question 6

A 32-year-old male has attempted suicide by ingesting pesticides. His clothes and body are soiled with the pesticides. He presents with excessive salivation and sweating, and his pupils are constricted. What is the most appropriate next step in management?

Accepted Answer

Remove contaminated clothing

Answer

Induce emesis

Answer

Administer atropine immediately

Answer

Administer Pralidoxime (PAM) immediately

Question 7

Vitriolage can be caused by which of the following plants?

Accepted Answer

Bhilawanol

Answer

Croton tiglium

Answer

Abrus precatorius

Answer

Calotropis

Question 8

The brain is preserved in all of the following types of poisoning, except:

Accepted Answer

Heavy metal poisoning

Answer

Organophosphate poisoning

Answer

Alkaloid poisoning

Answer

Volatile organic poisoning

Question 9

Which of the following is not a constituent of a universal antidote?

Accepted Answer

Potassium permanganate

Answer

Activated charcoal

Answer

Tannic acid

Answer

Magnesium oxide

Question 10

Itai Itai disease is caused by toxicity of:

Accepted Answer

Cadmium

Answer

Antimony

Answer

Lead

Answer

Mercury

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

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