Antidotes and Their Applications — MCQs
In case of cyanide poisoning, antidote of amyl nitrite is given. This is an example of:
Which among the following is an iron chelator?
Antidote for acetaminophen poisoning is?
Diazepam poisoning is treated by:
Atropine is not an antidote in:
A 5-year-old child who has taken 10 iron tablets presents with nausea and abdominal pain. What is the antidote of iron poisoning?
Which of the following is used as an antidote for organophosphorus poisoning?
A female, Lalita, aged 26 years takes 100 tablets of paracetamol. Treatment of choice is:
What is the treatment for Dabigatran toxicity?
Which one of the following is an antidote for Rivaroxaban and Apixaban, when reversal of anticoagulation is needed due to uncontrolled bleeding?
Antidotes and Their Applications Indian Medical PG Practice Questions and MCQs
Question 1: In case of cyanide poisoning, antidote of amyl nitrite is given. This is an example of:
- A. Receptor antagonism
- B. Chemical antagonism (Correct Answer)
- C. Physical antagonism
- D. Physiological antagonism
Explanation: ***Chemical antagonism*** - Amyl nitrite functions by inducing the formation of **methemoglobin**, which has a higher affinity for **cyanide ions** than cytochrome c oxidase. - This effectively sequesters cyanide, rendering it unable to bind to and inhibit the **cytochrome oxidase enzyme**, thus preventing its toxic effects [3]. *Receptor antagonism* - This involves a drug binding to a **receptor** and blocking the action of an **agonist**, without activating the receptor itself [1], [2]. - Amyl nitrite does not exert its effect by binding to a specific receptor and blocking cyanide's action; instead, it directly interacts with cyanide itself. *Physical antagonism* - This type of antagonism involves a drug preventing another drug's action through a **physical property**, such as adsorption or chelation. - While there is an interaction, the formation of methemoglobin and its subsequent binding to cyanide is more precisely described as a chemical reaction rather than a simple physical interaction or adsorption. *Physiological antagonism* - This occurs when two drugs act on **different receptors** or pathways to produce **opposite physiological effects**. - Amyl nitrite does not produce an opposite physiological effect by acting on a different pathway; rather, it directly counteracts the chemical nature of cyanide.
Question 2: Which among the following is an iron chelator?
- A. BAL
- B. Desferrioxamine (Correct Answer)
- C. EDTA
- D. Penicillamine
Explanation: ***Desferrioxamine*** - **Desferrioxamine** is a specific iron chelator used to treat **acute iron poisoning** and chronic iron overload, such as in patients with **thalassemia** requiring frequent transfusions. - It works by binding to free iron in the bloodstream and promoting its **excretion via urine**. *BAL* - **BAL (dimercaprol)** is primarily used as a chelating agent for **heavy metal poisoning**, particularly **arsenic, mercury, and lead** [1], [2]. - While it can chelate some metals, its affinity and primary use are not for iron. *EDTA* - **EDTA (ethylenediaminetetraacetic acid)** is a chelator often used for **lead poisoning** [1], [2] and hypercalcemia. - It has a high affinity for various divalent and trivalent metal ions [2], but it is not the primary or most specific iron chelator. *Penicillamine* - **Penicillamine** is a chelating agent primarily used for the treatment of **copper overload** in **Wilson's disease**. - It is also used in the treatment of severe **rheumatoid arthritis** and **cystinuria**, but not typically for iron chelation.
Question 3: Antidote for acetaminophen poisoning is?
- A. Penicillamine
- B. N-Acetyl cysteine (Correct Answer)
- C. Glycolamine
- D. Fomepizole
Explanation: ***N-Acetyl cysteine*** - **N-acetyl cysteine (NAC)** is the specific antidote for acetaminophen (paracetamol) poisoning, acting by replenishing hepatic **glutathione stores**. - **Glutathione** is crucial for detoxifying the toxic metabolite **N-acetyl-p-benzoquinone imine (NAPQI)**, preventing liver damage. *Penicillamine* - **Penicillamine** is a chelating agent used primarily in conditions like **Wilson's disease** (copper toxicity) and **rheumatoid arthritis**. - It has no role in the treatment or detoxification of **acetaminophen poisoning**. *Glycolamine* - **Glycolamine** is not a recognized pharmaceutical antidote for any specific poisoning. - This compound is not therapeutically relevant in toxicology scenarios, particularly for **acetaminophen overdose**. *Fomipezole* - **Fomepizole** is an antidote used for poisoning by **methanol** and **ethylene glycol**, not acetaminophen. - It works by inhibiting **alcohol dehydrogenase**, preventing the formation of toxic metabolites from these alcohols.
Question 4: Diazepam poisoning is treated by:
- A. Resins
- B. Hemofiltration
- C. Charcoal
- D. Flumazenil (Correct Answer)
Explanation: ***Flumazenil*** - **Flumazenil** is a **benzodiazepine receptor antagonist** that competitively binds to the benzodiazepine binding site on the GABA-A receptor, reversing the effects of diazepam. - It is used in cases of severe benzodiazepine overdose causing **respiratory depression** or **severe sedation**. *Resins* - **Resins**, such as **cholestyramine**, are typically used to bind toxins or drugs in the **gastrointestinal tract** that undergo enterohepatic recirculation. - They are generally not effective for reversing the central nervous system depression caused by a benzodiazepine overdose. *Hemofiltration* - **Hemofiltration** is a form of renal replacement therapy used to remove small and middle molecular weight substances from the blood. - While it can remove some drugs, **diazepam** is highly **lipophilic** and extensively **protein-bound**, making it poorly amenable to removal by hemofiltration. *Charcoal* - **Activated charcoal** is used to prevent the absorption of ingested toxins from the gastrointestinal tract. - It is effective when administered soon after ingestion but does not reverse the established effects of an absorbed drug like diazepam in an overdose situation.
Question 5: Atropine is not an antidote in:
- A. Baygon
- B. Parathion
- C. Endrin (Correct Answer)
- D. Tik 20
Explanation: ***Endrin*** - Endrin is an **organochlorine insecticide**, and its toxicity is primarily mediated through the central nervous system, causing seizures and neurological symptoms. - Atropine is an **anticholinergic drug** and is ineffective because organochlorines do not act on cholinergic receptors; therefore, it is not an antidote for endrin poisoning. *Baygon* - Baygon is a **carbamate insecticide**, which inhibits acetylcholinesterase, leading to cholinergic crisis. - Atropine is an appropriate antidote for Baygon poisoning, as it blocks the effects of excess acetylcholine at muscarinic receptors. *Parathion* - Parathion is an **organophosphate insecticide**, known for irreversible inhibition of acetylcholinesterase, resulting in severe cholinergic toxicity. - Atropine is a crucial antidote for parathion poisoning, used to counteract the muscarinic effects of acetylcholine accumulation. *Tik 20* - Tik 20 typically contains **organophosphate compounds** such as malathion or parathion, which are acetylcholinesterase inhibitors. - As an effective anticholinergic, atropine is indicated in the treatment of poisoning by organophosphates found in products like Tik 20.
Question 6: A 5-year-old child who has taken 10 iron tablets presents with nausea and abdominal pain. What is the antidote of iron poisoning?
- A. EDTA
- B. British Anti Lewisite
- C. Deferoxamine (Correct Answer)
- D. Penicillamine
Explanation: ***Deferoxamine*** - **Deferoxamine** is the chelating agent of choice for **iron poisoning**, forming a non-toxic complex that is excreted in urine. - It is indicated in patients with significant iron overdose, often presenting with **gastrointestinal symptoms** (nausea, abdominal pain), metabolic acidosis, or evidence of end-organ damage. *EDTA* - **EDTA (Calcium Disodium Versenate)** is primarily used to treat **lead poisoning** and sometimes other heavy metal intoxications [1]. - It is not effective for iron poisoning and can potentially worsen symptoms due to its affinity for calcium [1]. *British Anti Lewisite* - **British Anti Lewisite (BAL), or dimercaprol**, is an antidote for **arsenic, mercury, and gold poisoning** [2]. - It is not used for iron overdose and has a high incidence of side effects. *Penicillamine* - **Penicillamine** is another chelating agent used to treat **copper poisoning (Wilson's disease)** and sometimes lead or mercury poisoning. - It is not the primary antidote for iron poisoning and has a slower onset of action compared to deferoxamine.
Question 7: Which of the following is used as an antidote for organophosphorus poisoning?
- A. N-acetyl cysteine
- B. Physostigmine
- C. Flumazenil
- D. Pralidoxime aldoxime methiodide (PAM) (Correct Answer)
Explanation: ***Pralidoxime aldoxime methiodide (PAM)*** - **Pralidoxime (PAM)** is an **oxime reactivator** that works by regenerating the inhibited **acetylcholinesterase** enzyme, thereby reversing the effects of organophosphorus poisoning. - It is particularly effective in treating the **nicotinic symptoms** (e.g., muscle weakness, paralysis) of severe organophosphate poisoning. *N-acetyl cysteine* - **N-acetyl cysteine (NAC)** is the antidote for **acetaminophen (paracetamol) overdose**, not organophosphorus poisoning. - It works by replenishing **glutathione** stores, which are crucial for detoxifying acetaminophen metabolites. *Physostigmine* - **Physostigmine** is an **acetylcholinesterase inhibitor** that increases acetylcholine levels. - It is used to reverse the effects of **anticholinergic poisoning**, not organophosphorus poisoning, which overstimulates the cholinergic system. *Flumazenil* - **Flumazenil** is a **benzodiazepine receptor antagonist** used to reverse the sedative effects of **benzodiazepine overdose**. - It does not have any role in the treatment of organophosphorus poisoning.
Question 8: A female, Lalita, aged 26 years takes 100 tablets of paracetamol. Treatment of choice is:
- A. Lavage with charcoal
- B. Dialysis
- C. Alkaline diuresis
- D. Acetylcysteine (Correct Answer)
Explanation: ***Acetylcysteine*** - **Acetylcysteine** is the **antidote of choice** for paracetamol (acetaminophen) overdose, replenishing **glutathione stores** and detoxifying toxic paracetamol metabolites. - Early administration (within 8 hours of ingestion) is crucial for preventing **hepatic damage**, as it inhibits the binding of the toxic metabolite **NAPQI** to liver proteins. *Lavage with charcoal* - **Gastric lavage** and **activated charcoal** are primarily used for **decontamination** in the early stages (within 1-2 hours) of acute overdose, to prevent absorption. - Given the ingestion of **100 tablets**, a significant amount of paracetamol has likely already been absorbed, making these less effective as the sole treatment. *Dialysis* - **Dialysis** is generally reserved for severe cases of paracetamol overdose complicated by **acute liver failure** or other severe organ dysfunction, which requires elimination of paracetamol and its metabolites from the blood. - It is not the **first-line treatment** for acute paracetamol overdose itself, but rather a supportive measure for complications. *Alkaline diuresis* - **Alkaline diuresis** is sometimes used to enhance the elimination of **acidic drugs** like salicylates (aspirin) from the body. - Paracetamol is primarily metabolized by the liver into glucuronide and sulfate conjugates, which are then excreted, and its elimination is not significantly enhanced by **alkaline diuresis**.
Question 9: What is the treatment for Dabigatran toxicity?
- A. Protamine sulphate
- B. Andexanet alfa
- C. Idarucizumab (Correct Answer)
- D. Argatroban
Explanation: ***Idarucizumab*** - **Idarucizumab** is a specific humanized monoclonal antibody fragment (Fab) that directly binds to dabigatran and its metabolites, effectively **reversing its anticoagulant effects**. - It is indicated for patients requiring urgent reversal of dabigatran's anticoagulant effects due to life-threatening or uncontrolled bleeding, or for emergency surgery/urgent procedures. *Protamine sulphate* - **Protamine sulphate** is used to reverse the anticoagulant effects of **heparin** and low molecular weight heparins, but it is ineffective against direct oral anticoagulants like dabigatran. - Its mechanism involves forming a stable ion pair with heparin, neutralizing its activity. *Andexanet alfa* - **Andexanet alfa** is a recombinant modified human factor Xa (FXa) decoy protein used to reverse the anticoagulant activity of **FXa inhibitors** (e.g., rivaroxaban, apixaban). - It does not bind to or reverse the effects of direct thrombin inhibitors like dabigatran. *Argatroban* - **Argatroban** is a **direct thrombin inhibitor** (similar mechanism of action to dabigatran) and is used as an anticoagulant, particularly in patients with heparin-induced thrombocytopenia. - It would worsen dabigatran toxicity rather than treat it, as both drugs inhibit thrombin.
Question 10: Which one of the following is an antidote for Rivaroxaban and Apixaban, when reversal of anticoagulation is needed due to uncontrolled bleeding?
- A. Hydroxocobalamin
- B. Glucarpidase
- C. Andexanet Alfa (Correct Answer)
- D. Idarucizumab
Explanation: ***Andexanet Alfa*** - **Andexanet Alfa** is a **modified recombinant factor Xa molecule** that acts as a decoy to bind and sequester direct factor Xa inhibitors like rivaroxaban and apixaban. - It is specifically indicated for the reversal of anticoagulation in patients treated with **rivaroxaban** or **apixaban** experiencing life-threatening or uncontrolled bleeding [1]. *Hydroxocobalamin* - **Hydroxocobalamin** is an antidote for **cyanide poisoning**, not for anticoagulant reversal. - It works by binding to cyanide to form cyanocobalamin, which can be excreted, thereby detoxifying the patient. *Glucarpidase* - **Glucarpidase** is used to rapidly lower **methotrexate concentrations** in patients with delayed methotrexate elimination and associated toxicity. - It is an enzyme that hydrolyzes methotrexate into inactive metabolites, facilitating its clearance. *Idarucizumab* - **Idarucizumab** is a specific reversal agent for **dabigatran**, a direct thrombin inhibitor. - It is a monoclonal antibody fragment that binds to dabigatran with high affinity, neutralizing its anticoagulant effect.
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