General Principles of Toxicology — MCQs
A farmer with pinpoint pupils, increased secretions and urination. What is the most likely diagnosis?
Acetaminophen [Paracetamol] induced liver toxicity is due to which metabolite?
A patient is admitted with insomnia, agitation, diarrhea, dilated pupils, and sweating. What is the type of poisoning?
Which of these is the best for management of methanol poisoning?
Gastric lavage is contraindicated in?
Which of the following substances is a toxin but has also been historically used as a therapeutic emetic in poisoning management?
Gastric lavage is contraindicated in which of the following?
The antidote of paracetamol poisoning
All are features of organophosphorus poisoning, except:
An obese patient presented in casualty in an unconscious state, with a blood glucose level of 400 mg/dL and urine testing positive for sugar and ketones. Which drug is most useful in his management?
General Principles of Toxicology Indian Medical PG Practice Questions and MCQs
Question 1: A farmer with pinpoint pupils, increased secretions and urination. What is the most likely diagnosis?
- A. Alcohol poisoning
- B. Organophosphate poisoning (Correct Answer)
- C. Opioid poisoning
- D. Atropine poisoning
Explanation: ***Organophosphate poisoning*** - **Pinpoint pupils (miosis)**, **increased secretions** (salivation, lacrimation, bronchial secretions), and **urination** are classic signs of cholinergic crisis caused by organophosphate toxicity [1]. - The patient's profession as a **farmer** increases the likelihood of exposure to pesticides, which often contain organophosphates [1], [2]. *Alcohol poisoning* - While alcohol poisoning can cause CNS depression, it does not typically present with **pinpoint pupils** or **increased secretions** like salivation and urination. - Common signs include **ataxia**, **slurred speech**, **nausea**, and **vomiting**. *Opioid poisoning* - Opioid poisoning also causes **pinpoint pupils** and **CNS depression**, but it typically leads to **decreased secretions** and **urinary retention**, not increased urination [2]. - **Respiratory depression** is a hallmark feature, which is not highlighted here as a primary symptom. *Atropine poisoning* - Atropine is an anticholinergic agent, meaning it would cause the opposite effects of organophosphate poisoning [2]. - Symptoms would include **dilated pupils (mydriasis)**, **dry mouth**, **decreased secretions**, and **urinary retention**.
Question 2: Acetaminophen [Paracetamol] induced liver toxicity is due to which metabolite?
- A. Co-Q
- B. Cytochrome 'C'
- C. NAPQI (Correct Answer)
- D. N-acetylcysteine
Explanation: ***NAPQI*** - **N-acetyl-p-benzoquinone imine (NAPQI)** is a highly reactive and toxic metabolite produced during acetaminophen metabolism, especially in overdose situations [1, 3]. - When glutathione stores are depleted due to excessive NAPQI formation, this metabolite covalently binds to hepatic macromolecules, causing **hepatocellular damage and necrosis** [1, 3].*N-acetylcysteine* - **N-acetylcysteine (NAC)** is the antidote for acetaminophen overdose, not the toxic metabolite itself [2, 3]. - NAC works by replenishing hepatic **glutathione stores**, which helps detoxify NAPQI and prevent liver injury [2, 3].*Co-Q* - **Coenzyme Q10 (CoQ10)** is an endogenous antioxidant and electron carrier in the mitochondrial respiratory chain. - It is not a metabolite of acetaminophen and plays no direct role in acetaminophen-induced liver toxicity.*Cytochrome 'C'* - **Cytochrome c** is a protein involved in the electron transport chain in mitochondria and plays a critical role in apoptosis. - While cellular damage from NAPQI can eventually lead to cytochrome c release and apoptosis, cytochrome c itself is not a metabolite of acetaminophen or the direct cause of toxicity.
Question 3: A patient is admitted with insomnia, agitation, diarrhea, dilated pupils, and sweating. What is the type of poisoning?
- A. Cannabis
- B. Ecstasy
- C. Heroin
- D. Cocaine (Correct Answer)
Explanation: **Cocaine** - The symptoms of **insomnia, agitation, diarrhea, dilated pupils, and sweating** are classic manifestations of **sympathomimetic toxicity**, characteristic of cocaine poisoning. - Cocaine acts by **blocking the reuptake of norepinephrine, dopamine, and serotonin**, leading to excessive stimulation of the central and peripheral nervous systems. - This presentation represents a **pure sympathomimetic toxidrome** without additional complicating features, which is most classically associated with cocaine intoxication. *Heroin* - Heroin poisoning (opioid overdose) typically presents with **CNS depression**, including **respiratory depression**, **pinpoint pupils (miosis)**, and **constipation**, which are opposite to the symptoms described. - Patients are usually **sedated or comatose**, not agitated or insomniac. - This represents an **opioid toxidrome**, not a sympathomimetic one. *Cannabis* - Cannabis intoxication usually causes **conjunctival injection (red eyes)**, **tachycardia**, **dry mouth**, and **increased appetite**, often accompanied by euphoria or drowsiness. - While it can cause some anxiety/agitation in higher doses or naive users, it does **not cause mydriasis (dilated pupils)** or the severe physical stimulation seen here. - Cannabis does not produce a sympathomimetic toxidrome. *Ecstasy* - Ecstasy (MDMA) is also a sympathomimetic and can cause similar symptoms including agitation, dilated pupils, and sweating. - However, MDMA intoxication is more characteristically associated with **severe hyperthermia**, **hyponatremia**, **bruxism (teeth grinding)**, **serotonin syndrome**, and **rhabdomyolysis** in severe cases. - While both are sympathomimetics, the presentation described represents a **classic pure sympathomimetic picture** most consistent with **cocaine**, which is the more common cause of this toxidrome in clinical practice.
Question 4: Which of these is the best for management of methanol poisoning?
- A. Fomepizole (Correct Answer)
- B. Naltrexone
- C. Disulfiram
- D. Acamprosate
Explanation: ***Fomepizole*** - **Fomepizole** is a competitive inhibitor of **alcohol dehydrogenase**, the enzyme responsible for metabolizing methanol into toxic metabolites like formic acid. - By inhibiting this enzyme, it prevents the formation of these toxic metabolites, thereby reducing organ damage and metabolic acidosis in methanol poisoning. *Naltrexone* - **Naltrexone** is an **opioid receptor antagonist** used in the treatment of alcohol and opioid dependence. - It does not have any direct action on the metabolism of methanol or its toxic byproducts. *Disulfiram* - **Disulfiram** inhibits **aldehyde dehydrogenase**, leading to an unpleasant reaction when alcohol is consumed (flushing, nausea, vomiting). - It is used for alcohol cessation and has no role in the management of methanol poisoning. *Acamprosate* - **Acamprosate** is a medication used to reduce alcohol cravings in individuals recovering from alcohol dependence, possibly by modulating **glutamate neurotransmission**. - It does not directly affect the metabolism of methanol or mitigate its toxic effects.
Question 5: Gastric lavage is contraindicated in?
- A. Bicarbonate
- B. Hydrocarbons (Correct Answer)
- C. Organo-Phosphosphate poisoning
- D. PCM toxicity
Explanation: ***Hydrocarbons*** - Gastric lavage is contraindicated in **hydrocarbon poisoning** due to the high risk of **aspiration** [2]. - Aspiration of hydrocarbons can lead to severe **chemical pneumonitis**, which is often more life-threatening than the systemic toxicity from ingestion [2]. *Bicarbonate* - Ingesting a large amount of bicarbonate can cause **alkalosis** and electrolyte imbalances. - While gastric lavage is not typically the primary treatment for mild bicarbonate overdose, it is not absolutely contraindicated in cases of massive ingestion where there is a clear benefit to removing unabsorbed substance, especially if performed with proper airway protection [1], [3]. *Organo-Phosphosphate poisoning* - Gastric lavage is generally recommended for **organophosphate poisoning** if the patient presents within 1-2 hours of ingestion and is awake with an intact gag reflex, or with a protected airway [2]. - This helps remove unabsorbed poison and can reduce the systemic absorption of these highly toxic compounds. *PCM toxicity* - For **paracetamol (PCM) toxicity**, gastric lavage can be considered if the patient presents within 1-2 hours of ingestion and has ingested a potentially toxic dose, especially when activated charcoal is not immediately available or contraindicated [4]. - The primary treatment for PCM toxicity involves **N-acetylcysteine (NAC)**, but gastric emptying can play a role in reducing initial absorption [4].
Question 6: Which of the following substances is a toxin but has also been historically used as a therapeutic emetic in poisoning management?
- A. Thallium
- B. Copper sulphate (Correct Answer)
- C. Arsenic oxide
- D. Mercuric chloride
Explanation: ***Copper sulphate*** - **Copper sulphate** is a **potent toxin** that causes gastrointestinal irritation, hemolysis, hepatotoxicity, and acute renal failure upon ingestion. - It was **historically used as an emetic** to induce vomiting in certain poisoning cases for gastric decontamination, though this practice has been largely abandoned due to its own significant toxicity and the availability of safer alternatives. - This represents its dual nature: a poison itself, yet paradoxically used in poisoning management (not as an antidote, but as a gastric evacuant). *Thallium* - **Thallium** is a highly toxic heavy metal causing severe multi-organ failure, alopecia, peripheral neuropathy, and potentially fatal systemic toxicity. - It has **no therapeutic use** in poisoning management and is purely a toxicological concern. *Arsenic oxide* - **Arsenic oxide** (arsenic trioxide) is a well-known carcinogen and potent cellular poison that disrupts oxidative phosphorylation. - While it has modern therapeutic use in acute promyelocytic leukemia, it has **never been used in poisoning management** as an emetic or therapeutic agent. *Mercuric chloride* - **Mercuric chloride** is highly corrosive and causes severe gastrointestinal burns, acute tubular necrosis, and systemic mercury toxicity. - It is a **potent toxin with no therapeutic application** in poisoning management.
Question 7: Gastric lavage is contraindicated in which of the following?
- A. Organophosphorus Poisoning
- B. Dhatura poisoning
- C. Arsenic poisoning
- D. Kerosene poisoning (Correct Answer)
Explanation: ***Kerosene poisoning*** - Gastric lavage is contraindicated in **kerosene poisoning** due to the high risk of **aspiration pneumonitis**. - Kerosene is a **hydrocarbon**, and aspiration of even small amounts can cause severe lung damage. *Arsenic poisoning* - **Gastric lavage** can be performed in arsenic poisoning, especially if the ingestion occurred recently, to remove unabsorbed toxin. - Activated charcoal is less effective for arsenic, making lavage a more relevant intervention in acute settings. *Organophosphorus Poisoning* - Gastric lavage is generally recommended within an hour of ingestion for **organophosphorus poisoning** to remove the toxic substance. - This helps reduce systemic absorption and mitigate the severe **cholinergic crisis** caused by these agents. *Dhatura poisoning* - **Gastric lavage** is indicated in dhatura poisoning, particularly if presenting within a few hours of ingestion, to remove unabsorbed **atropine-like alkaloids**. - This helps in reducing the **anticholinergic effects** and improving patient outcomes.
Question 8: The antidote of paracetamol poisoning
- A. Sodium bicarbonate
- B. Flumazenil
- C. N-acetyl cysteine (Correct Answer)
- D. Naloxone
Explanation: ***N-acetyl cysteine*** - **N-acetyl cysteine (NAC)** is the specific antidote for **paracetamol (acetaminophen)** overdose. - NAC works by replenishing **glutathione stores** in the liver, which are crucial for detoxifying the toxic metabolite **N-acetyl-p-benzoquinone imine (NAPQI)**. *Sodium bicarbonate* - **Sodium bicarbonate** is used to treat **metabolic acidosis** and certain drug overdoses that cause cardiac toxicity, such as tricyclic antidepressants. - It does not have a direct role in detoxifying paracetamol or its metabolites. *Flumazenil* - **Flumazenil** is an antagonist at the **benzodiazepine receptor** and is used to reverse the sedative effects of benzodiazepine overdose. - It has no effect on paracetamol toxicity. *Naloxone* - **Naloxone** is an **opioid receptor antagonist** used to reverse the effects of opioid overdose. - It does not interact with the metabolic pathways or toxic effects of paracetamol.
Question 9: All are features of organophosphorus poisoning, except:
- A. Lacrimation
- B. Bradycardia
- C. Sweating
- D. Mydriasis (Correct Answer)
Explanation: ***Mydriasis*** - Organophosphorus poisoning leads to excessive **acetylcholine** activity, causing **miosis** (pinpoint pupils), not mydriasis. - Mydriasis would indicate **anticholinergic** effects, which are opposite to the symptoms of organophosphorus poisoning. *Lacrimation* - Excess **acetylcholine** stimulates **muscarinic receptors** in lacrimal glands, leading to excessive tear production. - This is a classic "SLUDGE" symptom (Salivation, Lacrimation, Urination, Defecation, Gastric upset, Emesis). *Bradycardia* - Increased **acetylcholine** activity at cardiac muscarinic receptors (M2 receptors) slows the heart rate, causing **bradycardia**. - This is a common and potentially dangerous cardiovascular effect of organophosphorus poisoning. *Sweating* - **Acetylcholine** acts on muscarinic receptors in secretory glands, including sweat glands, causing profuse **sweating**. - This is another characteristic cholinergic symptom due to widespread autonomic overstimulation.
Question 10: An obese patient presented in casualty in an unconscious state, with a blood glucose level of 400 mg/dL and urine testing positive for sugar and ketones. Which drug is most useful in his management?
- A. Glibenclamide
- B. Troglitazone
- C. Insulin (Correct Answer)
- D. Chlorpropamide
Explanation: Insulin - The patient presents with **hyperglycemia**, **ketonuria**, and an **unconscious state**, suggestive of **diabetic ketoacidosis (DKA)** or at least severe uncontrolled diabetes requiring urgent glucose management [1], [4]. - **Insulin therapy** is crucial for DKA management, as it lowers blood glucose, resolves ketosis, and helps correct electrolyte imbalances [3]. *Glibenclamide* - This is a **sulfonylurea** that stimulates insulin release from pancreatic beta cells. - It is **contraindicated in DKA** because the pancreas is often severely stressed or non-functional, and it can worsen hypoglycemia if given inappropriately [2]. *Troglitazone* - This is a **thiazolidinedione** (glitazone) which improves insulin sensitivity in peripheral tissues. - It is **not used for acute hyperglycemia or DKA** and was withdrawn from the market due to liver toxicity. *Chlorpropamide* - This is an older **first-generation sulfonylurea**, similar to glibenclamide, that stimulates insulin secretion. - It has a **long half-life** and a higher risk of **hypoglycemia**, making it unsuitable for acute, severe hyperglycemia like DKA [2].
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