Emergency Pharmacology — MCQs

Emergency Pharmacology Indian Medical PG Practice Questions and MCQs

Question 51: In a status epilepticus patient, first-line drug is

A. Phenytoin
B. Magnesium
C. Benzodiazepine (Correct Answer)
D. Barbiturates

Explanation: ***Benzodiazepine*** - **Benzodiazepines** are the first-line treatment for status epilepticus due to their rapid onset of action in enhancing **GABAergic inhibition** [1]. - They effectively terminate seizures by binding to **GABA-A receptors**, leading to increased chloride influx and neuronal hyperpolarization. *Phenytoin* - **Phenytoin** is a second-line antiepileptic drug that can be used if benzodiazepines are unsuccessful, but it is not the initial treatment [1]. - Its mechanism involves blocking **voltage-gated sodium channels** to stabilize neuronal membranes and prevent seizure propagation [2]. *Magnesium* - **Magnesium sulfate** is primarily used in status epilepticus caused by **eclampsia** or severe **hypomagnesemia**, not as a general first-line agent. - It acts by stabilizing neuronal excitability and reducing acetylcholine release at the neuromuscular junction. *Barbiturates* - **Barbiturates** (e.g., phenobarbital) are typically considered third-line agents for refractory status epilepticus due to their significant side effects, including **respiratory depression** and hypotension. - They potentiate **GABA-A receptor** activity, similar to benzodiazepines, but with a higher risk profile.

Question 52: Drug used in treatment of malignant hyperthermia is

A. Phenobarbitone
B. Dantrolene (Correct Answer)
C. Paracetamol
D. Diazepam

Explanation: ***Dantrolene*** - **Dantrolene** is a direct-acting **skeletal muscle relaxant** that works by preventing calcium release from the sarcoplasmic reticulum. - This mechanism effectively counteracts the excessive calcium efflux responsible for the sustained muscle contraction and hypermetabolic state in **malignant hyperthermia**. *Phenobarbitone* - **Phenobarbitone** is a barbiturate primarily used as an **anticonvulsant** and sedative-hypnotic. - It has no direct muscle relaxant properties or specific action to address the underlying pathophysiology of **malignant hyperthermia**. *Paracetamol* - **Paracetamol** (acetaminophen) is an **analgesic** and **antipyretic**. - While it can help manage fever, it does not address the fundamental muscle rigidity, metabolic acidosis, or **calcium dysregulation** characteristic of malignant hyperthermia. *Diazepam* - **Diazepam** is a benzodiazepine primarily used for its **anxiolytic**, sedative, and **anticonvulsant** properties, acting on GABA receptors. - It would not treat the underlying **muscle rigidity** and hypermetabolism of malignant hyperthermia, though it might reduce anxiety.

Question 53: Which of the following drugs is used for hyperkalemia?

A. Glucagon
B. Calcium gluconate (Correct Answer)
C. Sodium phosphate
D. Chloride salts

Explanation: ***Calcium gluconate*** - **Calcium gluconate** is a crucial drug for treating severe hyperkalemia because it **stabilizes the cardiac membrane**, protecting the heart from the cardiotoxic effects of high potassium. - While it does not lower potassium levels, its primary role is to **prevent arrhythmias** and electrical instability in the short term. *Glucagon* - **Glucagon** is primarily used to treat **hypoglycemia** by stimulating glucose production in the liver. - It has no direct role in lowering potassium levels or stabilizing cardiac membranes during hyperkalemia. *Sodium phosphate* - **Sodium phosphate** is used to treat **hypophosphatemia** or as a laxative, often in preparation for colonoscopies. - It does not have a role in the management of hyperkalemia. *Chloride salts* - **Chloride salts**, such as **sodium chloride**, are typically used for volume expansion or to correct **hyponatremia**. - They do not directly lower potassium levels or provide the immediate cardiac protection needed in hyperkalemia.

Question 54: Which of the following is the most effective antagonist for morphine overdose?

A. Buprenorphine
B. Nalorphine
C. Naloxone (Correct Answer)
D. Pentazocine

Explanation: ***Naloxone*** - **Naloxone** is a pure opioid antagonist that rapidly reverses the effects of opioid overdose by competing for and displacing opioids from the **mu-opioid receptors** - Its rapid onset of action (1-2 minutes IV) and high affinity for opioid receptors make it the drug of choice for treating **morphine overdose**, particularly in emergency settings - Has no intrinsic agonist activity, making it safe and effective for acute reversal *Buprenorphine* - **Buprenorphine** is a partial opioid agonist, meaning it produces some opioid effects but to a lesser degree than full agonists like morphine - While it can displace full agonists from receptors, it is primarily used in **opioid dependence treatment** rather than acute overdose reversal - Has a ceiling effect for respiratory depression and is not the first-line agent for emergency overdose management *Nalorphine* - **Nalorphine** is an older mixed agonist-antagonist that was historically used for opioid overdose - It has largely been replaced by **naloxone** due to its own opioid-like effects (agonist activity at kappa receptors) and less favorable side effect profile - Can cause respiratory depression itself, making it unsuitable for emergency use *Pentazocine* - **Pentazocine** is an opioid agonist-antagonist (kappa agonist, mu antagonist), meaning it acts as an agonist at some opioid receptors and an antagonist at others - This mixed action means it can precipitate **withdrawal symptoms** in opioid-dependent individuals and is not suitable for reversing a full opioid overdose - Used primarily for analgesia, not overdose reversal

Question 55: Drug of choice for beta antagonist toxicity is?

A. Adrenaline
B. Glucagon (Correct Answer)
C. ACE inhibitors
D. Dopamine

Explanation: ***Glucagon*** - **Glucagon** is the drug of choice for **beta-blocker overdose** because it bypasses the beta-adrenergic receptors and directly activates **adenylate cyclase** to increase intracellular cAMP [1]. - This action leads to increased heart rate and myocardial contractility, counteracting the cardiac depression caused by beta-blockers [1]. *Adrenaline* - **Adrenaline** (epinephrine) is a beta-agonist, but its effects are blunted in severe **beta-blocker overdose** due to **competitive antagonism** at beta receptors. - While it can be used for its alpha-agonist effects to increase blood pressure, its efficacy in reversing profound bradycardia and myocardial depression may be limited. *ACE inhibitors* - **ACE inhibitors** are used in the management of hypertension and heart failure, primarily by reducing **angiotensin II** formation and inhibiting **bradykinin** degradation. - They have no direct role in reversing the immediate cardiovascular effects of **beta-antagonist toxicity**. *Dopamine* - **Dopamine** is a **catecholamine** with dose-dependent effects, including positive inotropy and chronotropy at higher doses, but it relies on **adrenergic receptor activation**. - Its effects can be attenuated in **beta-blocker overdose**, similar to adrenaline, making it less effective than glucagon as first-line therapy.

Question 56: Which of the following is used in the second-line management of strychnine poisoning?

A. Physostigmine
B. Naloxone
C. Barbiturates (Correct Answer)
D. Diazepam

Explanation: ***Barbiturates*** - As a **second-line treatment**, barbiturates like phenobarbital are used to control **refractory seizures** and muscle spasms in strychnine poisoning when benzodiazepines are insufficient. - They enhance the effect of **GABA**, leading to central nervous system depression and muscle relaxation. *Physostigmine* - This is an **acetylcholinesterase inhibitor** and is primarily used to reverse the anticholinergic effects of certain poisonings, not strychnine. - It would worsen seizures by increasing **acetylcholine**, which can cause tremors and convulsions. *Naloxone* - Naloxone is an **opioid antagonist** used to reverse opioid overdose, which presents with respiratory depression and pinpoint pupils. - It has no role in treating strychnine poisoning, which primarily causes **muscle spasms** and seizures. *Diazepam* - Diazepam, a **benzodiazepine**, is the **first-line treatment** for seizures and muscle spasms in strychnine poisoning. - It works by enhancing the effects of **GABA** at the GABA-A receptor, thereby reducing neuronal excitability.

Question 57: Loading dose of MgSO4 (IV) for severe preeclampsia/eclampsia should be prepared as:

A. 8 ml 50% w/v plus 12 ml NS (Correct Answer)
B. 12 ml 50% w/v plus 8 ml NS
C. 4 ml 50% w/v plus 16 ml NS
D. 16 ml 50% w/v plus 4 ml NS

Explanation: **Correct: 8 ml 50% w/v plus 12 ml NS** - A common regimen for a magnesium sulfate loading dose for severe preeclampsia/eclampsia is **4-6 grams IV over 15-20 minutes**. - To achieve **4 grams** with a 50% w/v MgSO4 solution (meaning **50 grams per 100 mL** or **500 mg per mL**), you would need **8 mL** (4000 mg / 500 mg/mL = 8 mL), which is then diluted with **12 mL of normal saline** to create a 20 mL solution that can be infused. - This is the **standard loading dose** recommended by WHO and most international guidelines. *Incorrect: 12 ml 50% w/v plus 8 ml NS* - This combination would deliver **6 grams of MgSO4** (12 mL x 500 mg/mL). While 6 grams can be used as a loading dose in some protocols, the most common and widely taught initial recommendation for severe preeclampsia is **4 grams**. - A higher dose without specific clinical indication could increase the risk of **magnesium toxicity**. *Incorrect: 4 ml 50% w/v plus 16 ml NS* - This combination would deliver only **2 grams of MgSO4** (4 mL x 500 mg/mL). - A 2-gram loading dose is generally **insufficient** for preventing or treating eclamptic seizures in severe preeclampsia, as it may not achieve therapeutic magnesium levels quickly enough. *Incorrect: 16 ml 50% w/v plus 4 ml NS* - This combination would deliver **8 grams of MgSO4** (16 mL x 500 mg/mL). - An 8-gram loading dose is **excessively high** and carries a significant risk of **magnesium toxicity**, including respiratory depression and cardiac arrest.

Question 58: Which agent provides immediate passive immunity in post-exposure prophylaxis for rabies?

A. BCG vaccine
B. MMR vaccine
C. Tetanus toxoid
D. Rabies immunoglobulin (Correct Answer)

Explanation: ***Rabies immunoglobulin*** - Provides **immediate, passive immunity** by supplying pre-formed antibodies that neutralize the rabies virus before the body can produce its own antibodies. - It is administered directly into and around the **wound site** and intramuscularly, acting rapidly to prevent viral entry into the nervous system. *BCG vaccine* - This vaccine is used against **tuberculosis** and does not offer any protection against rabies. - It stimulates **active immunity** against *Mycobacterium tuberculosis* over several weeks, not immediate passive immunity. *MMR vaccine* - The MMR vaccine protects against **measles, mumps, and rubella** and has no role in rabies prophylaxis. - It induces **active immunity** to these specific viral diseases, requiring time for the immune system to develop antibodies. *Tetanus toxoid* - The tetanus toxoid vaccine provides **active immunity** against **tetanus** by stimulating the production of antibodies to the tetanus toxin. - It does not offer any protective effect against the rabies virus.

Question 59: Which agent is used to reverse opioid overdose?

A. Atropine
B. Protamine
C. Naloxone (Correct Answer)
D. Flumazenil

Explanation: ***Naloxone*** - **Naloxone** is an **opioid receptor antagonist** that competitively binds to opioid receptors, reversing the effects of opioid agonists. - It rapidly restores respiratory function and consciousness in individuals experiencing an **opioid overdose**. *Atropine* - **Atropine** is an **anticholinergic agent** used to treat bradycardia, organophosphate poisoning, and as a pre-anesthetic medication. - It does not have any direct action on opioid receptors and is ineffective in reversing an opioid overdose. *Protamine* - **Protamine** is a **heparin antagonist** used to reverse the anticoagulant effects of heparin. - It acts by forming a stable complex with heparin, thereby neutralizing its activity, and is unrelated to opioid overdose. *Flumazenil* - **Flumazenil** is a **benzodiazepine receptor antagonist** used to reverse the sedative effects of benzodiazepines. - While it reverses the effects of another class of central nervous system depressants, it has no activity on opioid receptors and is not indicated for opioid overdose.

Question 60: A 30-year-old male presents with hypoxia, cyanosis, and confusion. He is found to have methemoglobinemia. What is the most appropriate treatment?

A. Activated charcoal
B. Methylene blue (Correct Answer)
C. Corticosteroids
D. High-flow oxygen

Explanation: ***Correct: Methylene blue*** - **Methylene blue** acts as an electron acceptor in the presence of NADPH, reducing the ferric iron (Fe3+) in **methemoglobin** back to ferrous iron (Fe2+), thus reversing methemoglobinemia. - It is the **first-line treatment** for symptomatic methemoglobinemia, especially in patients with low oxygen saturation and signs of end-organ hypoxia. - Typical dose: **1-2 mg/kg IV over 5 minutes**, with improvement expected within 30-60 minutes. *Incorrect: Activated charcoal* - **Activated charcoal** is used for gastrointestinal decontamination in cases of oral poisoning by adsorbing toxins. - It does not directly treat **methemoglobinemia** or reverse the effects of toxins already absorbed into the bloodstream. *Incorrect: Corticosteroids* - **Corticosteroids** possess anti-inflammatory and immunosuppressive properties. - They are used in conditions like asthma or autoimmune disorders and have no role in the direct treatment of **methemoglobinemia**. *Incorrect: High-flow oxygen* - While oxygen delivery should be maintained, **high-flow oxygen** alone is ineffective in treating significant **methemoglobinemia**. - This is because **methemoglobin** cannot bind oxygen effectively, regardless of the partial pressure of inspired oxygen, making direct reversal with methylene blue necessary.

Practice by Chapter

Management of Anaphylaxis

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Drugs in Cardiac Arrest

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Status Epilepticus Management

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Acute Stroke Therapeutics

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Toxicological Emergencies

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Antidotes in Emergency Medicine

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Pain Management in Emergency

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Sedation and Paralysis in Emergency

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Drugs in Traumatic Emergencies

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Thrombolysis in Emergency Settings

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