Forensic Toxicology — MCQs

Forensic Toxicology Indian Medical PG Practice Questions and MCQs

Question 751: Which of the following drugs can cause a disulfiram-like reaction?

A. Acamprostate
B. Metronidazole (Correct Answer)
C. Tetracycline
D. Digitalis

Explanation: ### Explanation The correct answer is **Metronidazole**. **Mechanism of Action:** A **disulfiram-like reaction** occurs when certain drugs inhibit the enzyme **acetaldehyde dehydrogenase**. Under normal circumstances, alcohol is metabolized into acetaldehyde and then into acetic acid. When this enzyme is inhibited, acetaldehyde accumulates in the blood, leading to symptoms such as flushing, tachycardia, palpitations, nausea, vomiting, and hypotension. Metronidazole is the classic example of a drug that triggers this reaction when consumed with alcohol. **Analysis of Options:** * **Metronidazole (Correct):** It is a nitroimidazole antibiotic that interferes with alcohol metabolism, making it a high-yield topic for forensic toxicology and pharmacology. * **Acamprosate (Incorrect):** This drug is used to maintain abstinence in alcohol-dependent patients by modulating glutamatergic neurotransmission. It does *not* cause a disulfiram-like reaction. * **Tetracycline (Incorrect):** While it is a broad-spectrum antibiotic, it does not inhibit acetaldehyde dehydrogenase. * **Digitalis (Incorrect):** A cardiac glycoside used for heart failure and arrhythmias; its toxicity involves gastrointestinal upset and visual disturbances (xanthopsia), but not alcohol-related reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Other drugs causing Disulfiram-like reactions:** * **Antibiotics:** Cephalosporins (Cefoperazone, Cefotetan), Tinidazole, Griseofulvin. * **Sulfonylureas:** Chlorpropamide, Tolbutamide. * **Others:** Procarbazine (anticancer), Coprine (found in certain mushrooms). * **Treatment:** Management is primarily supportive (IV fluids and antiemetics). Fomepizole may be considered in severe cases. * **Patient Counseling:** Patients on Metronidazole must be advised to avoid alcohol during treatment and for at least **48–72 hours** after the last dose.

Question 752: Which of the following is NOT classified as a narcotic drug under the NDPS Act?

A. Marijuana
B. Ketamine (Correct Answer)
C. Cannabis
D. Heroin

Explanation: **Explanation:** The **Narcotic Drugs and Psychotropic Substances (NDPS) Act, 1985** classifies substances into three main categories: Narcotic Drugs, Psychotropic Substances, and Controlled Substances. **Why Ketamine is the correct answer:** Ketamine is classified as a **Psychotropic Substance** (Schedule X drug) under the NDPS Act, not a Narcotic Drug. It was added to the Schedule of the NDPS Act in 2014 to curb its abuse as a "club drug" or "date rape drug." Medically, it is a dissociative anesthetic that acts as an NMDA receptor antagonist. **Analysis of Incorrect Options:** * **Marijuana & Cannabis:** Under Section 2(iii) of the NDPS Act, Cannabis (Hemp) is explicitly defined as a **Narcotic Drug**. This includes charas (resin), ganja (flowering tops), and any mixture containing these. * **Heroin:** Also known as Diamorphine, it is a semi-synthetic opioid derived from morphine. It is classified as an **Opium Derivative** and is a potent Narcotic Drug under the Act. **High-Yield Clinical Pearls for NEET-PG:** * **Coca leaf, Opium, and Cannabis** are the three primary plant-based sources of Narcotic Drugs defined in the Act. * **LSD, MDMA (Ecstasy), and Ketamine** are categorized as Psychotropic Substances. * **Punishment:** The NDPS Act is known for its stringent, non-bailable penalties, which are graded based on the quantity seized (Small, Intermediate, or Commercial). * **Section 27:** Deals with punishment for the consumption of any narcotic drug or psychotropic substance.

Question 753: What is the fatal period in sulphuric acid poisoning?

A. 2-4 hours
B. 6-10 hours
C. 12-16 hours (Correct Answer)
D. 8-14 hours

Explanation: ### Explanation **1. Why Option C (12-16 hours) is Correct:** Sulphuric acid (Vitriol) is a powerful corrosive that causes intense tissue destruction through **liquefactive necrosis** and dehydration. In fatal cases, death typically occurs within **12 to 16 hours**. The primary causes of death during this period are **hypovolemic shock** (due to massive fluid loss and tissue destruction) or **perforation peritonitis** (due to the acid burning through the stomach wall). If death occurs more rapidly (within minutes), it is usually due to laryngeal edema and asphyxia. **2. Why the Other Options are Incorrect:** * **Option A (2-4 hours):** This is too short for the systemic effects of sulphuric acid to manifest fully. While laryngeal spasm can cause death this early, it is not the standard "fatal period" cited in forensic literature. * **Option B (6-10 hours) & Option D (8-14 hours):** These ranges are slightly shorter than the established forensic standard for sulphuric acid. While some patients may succumb in this timeframe, the classic textbook fatal period for NEET-PG purposes is specifically 12-24 hours, with **12-16 hours** being the most frequently tested interval. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vitriolage:** The act of throwing sulphuric acid on a person with intent to disfigure or kill. * **Stomach Appearance:** The stomach becomes charred, black, and friable (resembling "wet blotting paper"). This is due to the formation of **acid hematin**. * **Fatal Dose:** Approximately **10-15 ml** for an adult. * **Chalky White Teeth:** A characteristic sign in sulphuric acid poisoning due to the destruction of dental enamel (though more common in nitric acid, it can occur here). * **Contraindication:** Gastric lavage and emetics are strictly **contraindicated** due to the high risk of esophageal/gastric perforation.

Question 754: Datura seeds resemble which plant part?

A. Ricinus communis
B. Capsicum (Correct Answer)
C. Opium
D. None of the above

Explanation: **Explanation:** The seeds of **Datura stramonium** (Thorn apple) are frequently confused with the seeds of **Capsicum annuum** (Chilli) due to their striking physical similarity. This is a high-yield point in forensic toxicology, as accidental poisoning often occurs when Datura seeds are mistaken for edible chilli seeds. **Why Capsicum is Correct:** Both seeds are yellowish-brown, flattened, and kidney-shaped. However, they can be distinguished by specific morphological features: * **Datura:** Larger, thicker, and have a **pitted (reticulated) surface**. They possess a **double-layered edge** and an embryo that is curved towards the hilum. * **Capsicum:** Smaller, thinner, and have a **smooth surface**. They have a **single-layered edge** and a pungent smell/taste. **Analysis of Incorrect Options:** * **A. Ricinus communis (Castor):** These seeds are oval, mottled (brown with grey spots), and possess a prominent **caruncle** at one end. They contain the potent toxin ricin but do not resemble Datura. * **C. Opium (Papaver somniferum):** Opium seeds (poppy seeds) are tiny, kidney-shaped, and usually white or greyish-black. They are significantly smaller than Datura seeds and lack the characteristic pitting. **Clinical Pearls for NEET-PG:** * **Toxin:** Datura contains belladonna alkaloids (**Atropine, Hyoscine, Hyoscyamine**). * **Classic Presentation:** "Dry as a bone, red as a beet, blind as a bat, hot as a hare, and mad as a hatter." * **Diagnostic Test:** The **Mydriatic Test** (dropping the patient's urine into a cat's eye causes pupillary dilatation). * **Antidote:** **Physostigmine** is the specific antidote for central anticholinergic symptoms.

Question 755: Which of the following poisons retards putrefaction?

A. Aluminium phosphide
B. Lead
C. Arsenic (Correct Answer)
D. Copper

Explanation: **Explanation:** **Arsenic** is the correct answer because it is a potent enzyme inhibitor and protoplasmic poison. It retards putrefaction by inhibiting the growth of putrefactive bacteria and inactivating cellular enzymes required for autolysis. In cases of chronic arsenic poisoning, this leads to a phenomenon known as **"Mummification,"** where the body tissues are preserved for an unusually long duration, even after burial. This property is of significant medico-legal importance as it allows for the detection of arsenic in the hair, nails, and bones long after death. **Analysis of Incorrect Options:** * **Aluminium Phosphide (A):** Known as "Wheat Protein," it causes rapid death due to the release of phosphine gas. It does not have preservative properties; in fact, bodies may undergo normal or slightly accelerated decomposition depending on environmental factors. * **Lead (B):** While a heavy metal, lead does not significantly inhibit putrefactive bacteria to the extent of preserving the entire body. Its toxicity is primarily systemic (neurological and hematological). * **Copper (C):** Though copper salts have some antimicrobial properties, they are not recognized in forensic toxicology as agents that significantly retard the generalized putrefaction of a human cadaver. **High-Yield Clinical Pearls for NEET-PG:** * **Poisons retarding putrefaction:** Arsenic, Antimony, Mercury, Zinc Chloride, and Barium. * **Arsenic & Exhumation:** Because arsenic retards decay, it is the most common poison for which exhumation is performed. * **Mee’s Lines:** Transverse white bands on nails seen in arsenic poisoning. * **Raindrop Pigmentation:** Hyperpigmentation of the skin characteristic of chronic arsenicosis.

Question 756: A deceased woman was sent for an autopsy. She was found dead in a locked room with a heat stove still running. What is the most likely cause of death?

A. Cyanide poisoning
B. H₂S poisoning
C. Aluminium phosphide poisoning
D. CO poisoning (Correct Answer)

Explanation: ***CO poisoning***- The context of a deceased person in a locked room with a running heat stove points strongly to inhalation of **Carbon Monoxide (CO)**, a colorless, odorless gas produced by incomplete combustion.- CO has a very high affinity for **hemoglobin**, forming **carboxyhemoglobin**, which impairs oxygen transport and causes death via chemical **asphyxia**.*Cyanide poisoning*- Cyanide prevents cellular oxygen utilization (histotoxic hypoxia) by non-competitively inhibiting **cytochrome oxidase** in the mitochondria.- While highly fatal, cyanide is usually associated with the smell of **bitter almonds** at the scene and is not typically produced by household heat stoves.*H₂S poisoning*- **Hydrogen sulfide (H₂S)** poisoning is characterized by a distinctive odor of **rotten eggs** and is frequently associated with occupational exposure (e.g., sewers or drilling).- This gas also causes tissue hypoxia by inhibiting cellular respiration, but the circumstances described favor simple CO production from combustion.*Aluminium phosphide poisoning*- **Aluminium phosphide (ALP)** liberates **phosphine gas** upon exposure to moisture or stomach acid, leading to systemic toxicity.- This type of poisoning is usually due to deliberate ingestion of pesticides and causes severe effects, particularly on the **myocardium**, which is inconsistent with the presented scenario.

Question 757: In which poisoning is cherry red hypostasis seen on post-mortem examination?

A. CO Poisoning (Correct Answer)
B. Hydrogen sulphide
C. Yellow phosphorus
D. Hydrogen cyanide

Explanation: ***CO Poisoning***- **Cherry red hypostasis** is the hallmark post-mortem finding in fatal **carbon monoxide (CO)** poisoning.- The bright red color is due to the formation of stable **carboxyhemoglobin (COHb)**, which retains this color even when blood pools after death.*Hydrogen sulphide* - Post-mortem findings usually include a **dark, tarry blood** consistency and the characteristic odor of **rotten eggs**.- It primarily acts by inhibiting cellular respiration, leading to asphyxia, but does not produce a bright red compound in the blood.*Yellow phosphorus*- This poisoning primarily causes severe **gastrointestinal irritation**, followed by fatal liver and kidney damage, leading to **jaundice**.- Post-mortem signs may include massive **hepatic necrosis** and luminescence (glowing) of the skin or vomit in the dark.*Hydrogen cyanide*- Cyanide poisoning can sometimes produce a pinkish flush or generalized redness but is typically associated with the odor of **bitter almonds**.- It causes cellular asphyxia by blocking **cytochrome c oxidase**, resulting in highly oxygenated venous blood (arterialization), but not the intense **cherry red** hue of CO poisoning.

Question 758: A 28-year-old male is brought to the emergency department unconscious after allegedly consuming an unknown substance. On examination, he has pin-point pupils, respiratory depression, and bradycardia. What is the most likely substance involved?

A. Opioid poisoning (Correct Answer)
B. Atropine poisoning
C. Benzodiazepine overdose
D. Organophosphate poisoning

Explanation: ***Opioid poisoning*** - The classic triad of **opioid overdose** is altered mental status (unconsciousness/coma), **pin-point pupils (miosis)**, and profound **respiratory depression**. - Opioids depress the central respiratory drive and often cause **bradycardia** and hypotension due to central vagal stimulation. - This is the **most likely diagnosis** given the complete clinical picture. *Atropine poisoning* - Atropine causes **anticholinergic toxidrome** characterized by mydriasis (dilated pupils), **tachycardia**, hyperthermia, dry flushed skin, and urinary retention. - The presentation is opposite to what is seen here - this patient has **miosis and bradycardia**, not mydriasis and tachycardia. *Benzodiazepine overdose* - Benzodiazepine overdose causes significant CNS depression (sedation, coma) but typically maintains **normal respiratory function** when taken alone. - The pupils are usually mid-range or normal, and **pinpoint pupils** with marked respiratory depression and bradycardia are not characteristic features. *Organophosphate poisoning* - Organophosphate poisoning causes the **cholinergic toxidrome** (SLUDGE syndrome: Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis). - While it can cause **miosis and bradycardia**, patients typically also have excessive secretions, sweating, muscle fasciculations, and characteristic **garlic/petroleum odor**. - The absence of hypersecretion and fasciculations makes this less likely.

Question 759: One of the following statements regarding venom is incorrect:

A. Viperidae - Hemotoxic
B. Elapidae - Myotoxic (Correct Answer)
C. Common krait - Neurotoxic
D. Common cobra - Neurotoxic

Explanation: ***Elapidae - Myotoxic*** - This statement is **incorrect**. Venom from the **Elapidae** family (e.g., cobras, kraits, mambas) is **predominantly neurotoxic**, affecting the nervous system and causing paralysis. - The primary target of Elapidae venom is the **neuromuscular junction**, leading to respiratory failure, not muscle degeneration (myotoxicity). - While some Elapidae subspecies (certain sea snakes, Australian elapids) may have myotoxic components, the family is **classically characterized as neurotoxic**, especially in the Indian context where cobras and kraits are the main representatives. ***Common cobra - Neurotoxic*** - This statement is **correct**. The venom of the **Common Cobra** (Naja naja), which belongs to the Elapidae family, is highly **neurotoxic**. - It primarily contains long and short-chain neurotoxins that cause rapid, progressive **paralysis** and respiratory failure. ***Common krait - Neurotoxic*** - This statement is **correct**. **Common Krait** (Bungarus caeruleus), also an Elapid, possesses venom that is highly potent and entirely **neurotoxic**. - Krait venom often causes severe, often delayed, **neuromuscular blockade** and paralysis, making it one of the most dangerous snakes in India. ***Viperidae - Hemotoxic*** - This statement is **correct**. Venom from the **Viperidae** family (e.g., Russell's viper, saw-scaled viper) is mainly **hemotoxic** and **cytotoxic**. - It primarily targets the blood and vascular system, causing coagulopathy, massive tissue necrosis, bleeding disorders, and often **disseminated intravascular coagulation (DIC)**.

Question 760: In which of the following poisonings does silver nitrate impregnated filter paper turn black when exposed to gastric lavage contents?

A. Malathion
B. Opium
C. Barbiturates
D. Aluminium phosphide (Correct Answer)

Explanation: ***Aluminium phosphide*** - Aluminium phosphide ($AlP$) reacts vigorously with water or gastric acid to release highly toxic **phosphine gas** ($PH_3$). - Phosphine gas is a strong reducing agent that reacts with **silver nitrate ($AgNO_3$)** impregnated paper, reducing it to black **metallic silver ($Ag$)** and thus turning the paper black, a method known as the field test for Celphos. ***Malathion*** - Malathion is an **organophosphate insecticide**, and its poisoning is diagnosed primarily by clinical features of cholinergic crisis (SLUDGE syndrome) and measuring depressed **serum/RBC cholinesterase levels**. - Organophosphates do not release phosphine gas and therefore do not produce a positive reaction with silver nitrate filter paper. ***Barbiturates*** - Barbiturate poisoning is confirmed using tests like the **Dille-Koppanyi test** (for color change) or advanced **chromatographic methods** on blood or urine samples. - The barbiturate structure does not produce a reducing gas like phosphine upon reaction, so the silver nitrate paper test would remain negative. ***Opium*** - Opium poisoning (due to alkaloids like **morphine**) is confirmed by detecting the drug or its metabolites in urine or blood using **immunoassays** or gas/liquid chromatography. - Opium alkaloids are not detected by this specific qualitative test, as it is designed to detect the highly reducing nature of phosphine gas.

Practice by Chapter

General Principles of Toxicology

Practice Questions

Corrosive Poisons

Practice Questions

Metallic Poisons

Practice Questions

Non-Metallic Poisons

Practice Questions

Organic Irritant Poisons

Practice Questions

Neurotic Poisons

Practice Questions

Cardiac Poisons

Practice Questions

Asphyxiant Poisons

Practice Questions

Food Poisoning

Practice Questions

Drug Abuse and Dependence

Practice Questions

Analytical Toxicology Methods

Practice Questions

Interpretation of Toxicology Results

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free