Forensic Toxicology Practice Questions

Q: In nux vomica poisoning, which of the following organs also requires preservation?

Brain. ### Explanation In cases of **Nux vomica (Strychnine)** poisoning, the **Brain and Spinal Cord** are essential organs for preservation during autopsy, in addition to the routine viscera (stomach, liver, kidney, and spleen). **Why the Brain?** Strychnine is a potent spinal stimulant that acts by competitively inhibiting **Glycine**, an inhibitory neurotransmitter. It primarily affects the motor neurons of the spinal cord and the brainstem. Because Strychnine is highly resistant to putrefaction and tends to concentrate in the central nervous system (CNS), the brain and spinal cord are preserved to ensure the detection of the alkaloid during toxicological analysis, especially in decomposed bodies. **Analysis of Incorrect Options:** * **A. Long bones:** These are typically preserved in cases of heavy metal poisoning (e.g., Lead, Arsenic) or when the body is completely skeletonized. * **C. Muscles:** While strychnine causes violent muscular spasms (opisthotonus), the toxin itself is better detected in the CNS or solid viscera rather than muscle tissue. * **D. Skin:** Skin (and underlying fat) is preserved in cases of poisoning by injection (e.g., Insulin or Snakebite) to detect the local site of entry. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Competitive antagonism of Glycine at the post-synaptic receptor. * **Clinical Sign:** **Risus Sardonicus** (fixed grin due to facial muscle spasm) and **Opisthotonus** (arch-like bowing of the back). * **Mind the Difference:** Unlike Tetanus, in Nux vomica poisoning, the muscles **relax completely** between convulsions. * **Post-mortem finding:** Early onset and rapid disappearance of Rigor Mortis due to exhaustion of ATP from convulsions. * **Fatal Dose:** 50–100 mg of Strychnine (one crushed seed).

Q: Which of the following is NOT a nerve gas?

Bromo Benzyl Cyanide. The correct answer is **Bromo Benzyl Cyanide (BBC)** because it is a **Lachrymatory agent (Tear Gas)**, not a nerve gas. ### 1. Why Bromo Benzyl Cyanide is the Correct Answer Nerve gases are organophosphorus compounds that inhibit acetylcholinesterase, leading to a cholinergic crisis. In contrast, **Bromo Benzyl Cyanide (BBC)** belongs to the category of **War Gases** known as **Irritants/Lachrymators**. Its primary action is to cause intense irritation to the eyes, leading to involuntary closing of eyelids and temporary blindness. It does not affect the nervous system via the cholinergic pathway. ### 2. Analysis of Incorrect Options (Nerve Gases) The other options belong to the **G-series** of nerve agents, developed primarily by Germany during WWII: * **Tabun (GA):** The first nerve agent discovered; it is an ethyl phosphoramidocyanidate. * **Sarin (GB):** A highly volatile liquid; it is the most well-known nerve gas used in chemical warfare. * **Soman (GD):** Similar to Sarin but more toxic and characterized by "aging" (irreversible binding to the enzyme) occurring much faster. ### 3. High-Yield Clinical Pearls for NEET-PG * **Mechanism of Nerve Gases:** Irreversible inhibition of **Acetylcholinesterase (AChE)** $\rightarrow$ Accumulation of Acetylcholine $\rightarrow$ SLUDGE syndrome (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis). * **Antidote for Nerve Gas:** Atropine (physiological antagonist) + Oximes like Pralidoxime (enzyme reactivator). * **VX Gas:** The most potent and lethal nerve agent (V-series). * **Other War Gases:** * *Vesicants (Blistering):* Mustard gas, Lewisite. * *Choking agents:* Phosgene, Chlorine. * *Lachrymators:* CN (Mace), CS, and BBC.

Q: A sample of spinal cord is preserved in suspected poisoning with?

Strychnine. **Explanation:** In forensic toxicology, the choice of viscera for preservation depends on the pharmacokinetics and target organs of the specific poison. **Why Strychnine is Correct:** Strychnine is a potent spinal poison derived from *Strychnos nux-vomica*. It acts by competitively inhibiting **glycine**, an inhibitory neurotransmitter, at the postsynaptic receptor sites in the **anterior horn cells of the spinal cord**. This leads to unchecked neuronal stimulation and severe tetanic convulsions. Because the spinal cord is the primary site of action and where the toxin concentrates, it is the mandatory sample to preserve (along with the brain) in suspected cases of strychnine poisoning. **Analysis of Incorrect Options:** * **Arsenic:** As a heavy metal, arsenic deposits in keratinized tissues. High-yield samples include **hair, nails, and bone**, in addition to routine viscera (liver/kidney). * **Alcohol:** Being highly volatile, alcohol is best detected in **blood, vitreous humor, or urine**. Spinal cord tissue is not a standard sample for ethanol analysis. * **Oleander:** This is a cardiac poison containing glycosides (like neriin). Diagnosis relies on routine viscera (stomach contents, liver, kidney) and **blood** for LC-MS analysis. **NEET-PG High-Yield Pearls:** * **Strychnine Convulsions:** Characterized by *Opisthotonus* (back arching), *Risus Sardonicus* (facial grimacing), and *Pleurothotonus* (lateral arching). * **Differential Diagnosis:** Often confused with Tetanus; however, in strychnine poisoning, muscles relax completely between convulsions. * **Preservative:** Saturated solution of **Common Salt** is used for most viscera, but **Rectified Spirit** is preferred for most poisons *except* alcohol, acetic acid, and paraldehyde.

Q: In which of the following poisonings does formication and insanity occur together?

Cocaine. **Explanation:** The correct answer is **Cocaine**. The combination of formication and insanity is a classic clinical presentation of chronic cocaine toxicity. **1. Why Cocaine is Correct:** Chronic cocaine abuse leads to a specific tactile hallucination known as **formication** (also called **Magnan’s symptom** or "cocaine bugs"). The patient experiences a sensation of insects crawling under or over the skin, often leading to self-mutilation and excoriations as they try to "dig out" the bugs. When this occurs alongside **Cocaine Psychosis** (insanity), characterized by paranoid delusions and extreme agitation, it forms a diagnostic hallmark of the drug's effect on the dopaminergic system. **2. Why Other Options are Incorrect:** * **LSD:** Primarily causes visual hallucinations and synesthesia (seeing sounds/hearing colors). While it causes "insanity-like" states (bad trips), formication is not a characteristic feature. * **Amphetamine:** Can cause "Amphetamine Psychosis" which mimics schizophrenia, and occasionally formication. However, in forensic examinations, the specific triad of formication, cocaine bugs, and Magnan’s symptom is classically attributed to Cocaine. * **Cannabis:** Typically leads to euphoria, altered time perception, or "Run Amok" (in acute toxicity). It does not typically present with formication. **3. High-Yield Clinical Pearls for NEET-PG:** * **Magnan’s Symptom:** Tactile hallucination specific to Cocaine. * **Body Packers/Stuffers:** Individuals who swallow cocaine packets; rupture leads to fatal toxicity. * **Adulterant:** Cocaine is often mixed with **Levamisole**, which can cause agranulocytosis. * **Sudden Death:** Cocaine causes coronary vasospasm and fatal arrhythmias (even in young users). * **Pupils:** Cocaine causes **Mydriasis** (dilated pupils), unlike Opioids which cause Miosis.

Q: Percentage of COHb that usually causes death?

> 70%. **Explanation:** Carbon monoxide (CO) poisoning occurs due to its high affinity for hemoglobin (200–250 times greater than oxygen), forming **Carboxyhemoglobin (COHb)**. This shifts the oxygen-dissociation curve to the left, leading to cellular hypoxia. **Why Option C is Correct:** In forensic toxicology, a COHb level **> 70%** is generally considered the lethal threshold in a healthy individual. At this concentration, the oxygen-carrying capacity of the blood is so severely compromised that oxidative phosphorylation ceases, leading to rapid respiratory failure and death. **Analysis of Incorrect Options:** * **Option A (> 50%):** At 50–60% saturation, patients experience severe symptoms like syncope, seizures, and coma, but it is not typically the definitive lethal level unless the patient has pre-existing cardiovascular disease. * **Option B (> 60%):** While 60% is often cited as the beginning of the "fatal range," most forensic textbooks (like Reddy and Pillay) specify that levels exceeding 70% are the standard finding in CO-related fatalities. * **Option D (> 80%):** Death usually occurs well before reaching 80%. Such high levels are rarely seen because respiratory arrest occurs earlier. **High-Yield Clinical Pearls for NEET-PG:** * **Cherry Red Discoloration:** A classic post-mortem finding in skin, mucous membranes, and viscera (due to COHb). * **CT/MRI Finding:** Bilateral necrosis of the **Globus Pallidus** is a pathognomonic sign of CO poisoning. * **Treatment:** 100% Oxygen (reduces COHb half-life from 5 hours to 80 minutes). Hyperbaric oxygen is the treatment of choice for severe cases. * **Specimen Preservation:** Blood for COHb analysis should be preserved under a layer of **liquid paraffin** to prevent gas loss.

Q: All of the following are seen in lead poisoning except?

Hallucinations. **Explanation:** Lead poisoning (Plumbism) is a multisystemic disorder primarily affecting the gastrointestinal, hematological, and nervous systems. The correct answer is **Hallucinations**, as they are characteristic of **acute poisoning with organic lead** (e.g., tetraethyl lead) or other toxic states, but are not a typical feature of chronic inorganic lead poisoning (the most common form tested). **Analysis of Options:** * **A. Hallucinations (Correct):** While organic lead can cause "lead psychosis" with hallucinations, it is not a standard feature of classic plumbism. Hallucinations are more classically associated with alcohol withdrawal (Delirium Tremens) or poisoning by Datura and Cannabis. * **B. GIT disturbances:** These are early and common signs. Patients present with **Lead Colic** (severe abdominal pain relieved by pressure) and chronic constipation. * **C. Peripheral neuritis:** Lead typically causes motor neuropathy. The classic presentation is **Wrist Drop** and **Foot Drop** due to paralysis of the extensor muscles (radial and peroneal nerves), though sensory loss is rare. * **D. Encephalitis (Lead Encephalopathy):** This is a severe manifestation, more common in children. It presents with increased intracranial pressure, convulsions, and coma due to cerebral edema. **High-Yield Clinical Pearls for NEET-PG:** * **Burtonian Line:** A characteristic blue-purple line on the gums due to lead sulfide deposition. * **Basophilic Stippling:** Punctate basophilia in RBCs (due to inhibition of pyrimidine-5'-nucleotidase). * **Enzymes Inhibited:** ALA dehydratase and Ferrochelatase (leading to increased Coproporphyrin III in urine). * **Radiology:** "Lead lines" (increased density) at the metaphyses of growing long bones in children. * **Treatment:** DOC is **Succimer (DMSA)** for outpatient management; **BAL and EDTA** are used for encephalopathy.

Q: Widmark's formula is used for the estimation of?

Alcohol. **Explanation:** **Widmark’s Formula** is a mathematical calculation used in forensic toxicology to estimate the amount of **Alcohol (Ethanol)** consumed by an individual or to determine the blood alcohol concentration (BAC) at a specific time. The formula is expressed as: **$A = c \times p \times r$** * **A:** Amount of alcohol absorbed (in grams). * **c:** Blood alcohol concentration (in mg/g). * **p:** Weight of the person (in kg). * **r:** Widmark’s factor (average distribution of alcohol in the body; approx. 0.68 for men and 0.55 for women). **Why other options are incorrect:** * **Cyanides:** Toxicity is measured via blood cyanide levels (lethal dose ~200 mg), but no specific eponymous formula like Widmark’s is used for estimation. * **D.D.T. (Organochlorine):** Estimation is done via gas chromatography; it is stored in body fat, but Widmark’s formula does not apply. * **Teeth:** Dental estimation involves methods like **Gustafson’s Method** (for age) or **Boyde’s Method**, not Widmark’s. **High-Yield Clinical Pearls for NEET-PG:** 1. **Mellanby Effect:** Clinical impairment is more pronounced when the blood alcohol level is rising than when it is falling at the same concentration. 2. **Elimination Rate:** Alcohol is metabolized by zero-order kinetics at an average rate of **15 mg/dL/hour**. 3. **Legal Limit:** In India, the legal limit for driving is **30 mg/100 ml** of blood (Section 185 of the Motor Vehicles Act). 4. **Specimen of Choice:** In living persons, blood (from a peripheral vein) or breath is used; in the deceased, **Vitreous Humor** is the gold standard as it is resistant to putrefaction.

Q: Proximal tubule proteinuria and painful bone lesions are seen in overdose of which substance?

Cadmium. **Explanation:** The clinical presentation of **proximal tubule proteinuria** and **painful bone lesions** is the hallmark of chronic **Cadmium** poisoning. **Why Cadmium is correct:** Cadmium is a heavy metal that accumulates primarily in the kidneys. Chronic exposure leads to damage of the proximal convoluted tubules (PCT), resulting in **Fanconi-like syndrome**. This causes low-molecular-weight proteinuria (e.g., Beta-2 microglobulinuria), glucosuria, and aminoaciduria. Furthermore, cadmium interferes with calcium metabolism and Vitamin D activation, leading to osteomalacia and osteoporosis. This specific combination of renal failure and excruciatingly painful bone fractures was historically termed **"Itai-Itai" (Ouch-Ouch) disease** in Japan. **Why the other options are incorrect:** * **Lead:** Chronic lead poisoning (Plumbism) typically presents with abdominal colic, wrist drop/foot drop, Burtonian lines on gums, and microcytic hypochromic anemia with basophilic stippling. While it affects the kidneys (interstitial nephritis), it does not typically cause the "painful bone" syndrome. * **Mercury:** Acute poisoning causes corrosive GI damage and acute tubular necrosis. Chronic poisoning (Hydrargyrism) presents with tremors (Danbury tremor), erethism (psychological changes), and acrodynia (Pink disease). * **Phenol:** Phenol is a corrosive organic acid. Poisoning leads to carboluria (greenish-black urine), local necrosis, and systemic CNS/CVS collapse, but not chronic bone lesions. **High-Yield Facts for NEET-PG:** * **Itai-Itai Disease:** Caused by cadmium-contaminated water used for rice irrigation. * **Source:** Cadmium is found in rechargeable batteries, electroplating, and cigarette smoke. * **Marker:** Urinary Beta-2 microglobulin is a sensitive marker for cadmium-induced renal damage. * **Treatment:** Chelation is generally ineffective for chronic cadmium poisoning; prevention of exposure is key.

Q: Which of the following is a somniferous toxin?

Opium. **Explanation:** Toxicology classifies poisons based on their primary physiological effects. **Somniferous poisons** are substances that induce deep sleep, stupor, or narcosis by depressing the Central Nervous System (CNS). **1. Why Opium is Correct:** Opium, derived from *Papaver somniferum*, contains alkaloids like morphine and codeine. These act on opioid receptors in the brain, leading to analgesia, sedation, and a characteristic state of stupor. In forensic medicine, Opium is the classic example of a somniferous toxin, often presenting with the triad of pinpoint pupils, respiratory depression, and coma. **2. Why Other Options are Incorrect:** * **Dhatura & Belladonna (Options A & C):** These are classified as **Deliriant poisons** (Cerebral/Inebriant group). They contain anticholinergic alkaloids (Atropine, Hyoscine, Hyoscyamine) that cause CNS excitation, leading to "low-grade" delirium, hallucinations, and dilated pupils, rather than sleep. * **Cannabis (Option D):** This is classified as a **Hallucinogen** or **Inebriant**. While it can cause drowsiness in high doses, its primary forensic classification is based on its ability to cause euphoria, altered perception of time/space, and hallucinations. **Clinical Pearls for NEET-PG:** * **Somniferous Group:** Includes Opium and its alkaloids (Morphine, Heroin). * **Inebriant Group:** Includes Alcohol, Cannabis, and Chloroform. * **Deliriant Group:** Includes Dhatura, Belladonna, and Cannabis (Cannabis is sometimes cross-classified). * **Antidote for Opium:** Naloxone (Competitive antagonist). * **Fatal sign in Opium poisoning:** "Pinpoint pupils" which do not react to light (though they may dilate terminally due to asphyxia).

Question 1

In nux vomica poisoning, which of the following organs also requires preservation?

Accepted Answer

Brain

Answer

Long bones

Answer

Muscles

Answer

Skin

Question 2

Metabolic acidosis is not seen in the poisoning of which of the following substances?

Accepted Answer

Organophosphorus

Answer

Salicylate

Answer

Ethanol

Answer

Ethylene glycol

Question 3

Which of the following is NOT a nerve gas?

Accepted Answer

Bromo Benzyl Cyanide

Answer

Tabun

Answer

Sarin

Answer

Soman

Question 4

A sample of spinal cord is preserved in suspected poisoning with?

Accepted Answer

Strychnine

Answer

Arsenic

Answer

Alcohol

Answer

Oleander

Question 5

In which of the following poisonings does formication and insanity occur together?

Accepted Answer

Cocaine

Answer

Lysergic acid diethylamide (LSD)

Answer

Amphetamine

Answer

Cannabis

Question 6

Percentage of COHb that usually causes death?

Accepted Answer

> 70%

Answer

> 50%

Answer

> 60%

Answer

> 80%

Question 7

All of the following are seen in lead poisoning except?

Accepted Answer

Hallucinations

Answer

GIT disturbances

Answer

Peripheral neuritis

Answer

Encephalitis

Question 8

Widmark's formula is used for the estimation of?

Accepted Answer

Alcohol

Answer

Cyanides

Answer

D.D.T.

Answer

Teeth

Question 9

Proximal tubule proteinuria and painful bone lesions are seen in overdose of which substance?

Accepted Answer

Cadmium

Answer

Lead

Answer

Mercury

Answer

Phenol

Question 10

Which of the following is a somniferous toxin?

Accepted Answer

Opium

Answer

Dhatura

Answer

Belladonna

Answer

Cannabis

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

On this page

Practice by Chapter

Want unlimited practice?