Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology Indian Medical PG Practice Questions and MCQs

Question 751: Which of the following drugs is most associated with neuroleptic malignant syndrome?

A. Clozapine
B. Quetiapine
C. Olanzapine
D. Haloperidol (Correct Answer)

Explanation: ***Haloperidol*** - **Haloperidol** is a potent **first-generation antipsychotic** that strongly blocks **D2 dopamine receptors**. - This strong dopamine antagonism, particularly in the **nigrostriatal pathway**, is a primary mechanism underlying the development of **Neuroleptic Malignant Syndrome (NMS)**. *Clozapine* - Although clozapine is an antipsychotic, it is associated with a **lower risk of NMS** compared to high-potency typical antipsychotics. - Its unique pharmacological profile, including **weak D2 receptor blockade** and antagonism of other receptors, contributes to its reduced NMS risk. *Quetiapine* - Quetiapine is an **atypical (second-generation) antipsychotic** known for its **low risk of extrapyramidal symptoms (EPS)** and thus NMS. - Its relatively **loose binding to D2 receptors** and rapid dissociation significantly lowers the likelihood of severe dopamine blockade. *Olanzapine* - Olanzapine is another **atypical antipsychotic** with a **lower incidence of NMS** compared to typical antipsychotics like haloperidol. - While it has D2 receptor antagonism, it is less potent and more balanced by other receptor effects, leading to a reduced risk of NMS.

Question 752: Cannabidiol is not used for

A. Rett syndrome (Correct Answer)
B. Lennox-Gastaut syndrome
C. Dravet syndrome
D. Tuberous sclerosis complex

Explanation: ***Rett syndrome*** - **Cannabidiol (CBD)** is not an approved or commonly used treatment for Rett syndrome, which is a **neurodevelopmental disorder** primarily affecting girls. - Treatment for Rett syndrome focuses on managing symptoms with supportive care, **physiotherapy**, occupational therapy, and medications for specific issues like seizures or gastrointestinal problems. *Dravet syndrome* - **Cannabidiol (Epidiolex)** is approved in many regions for the treatment of seizures associated with **Dravet syndrome**, a severe form of epilepsy. - It works by modulating the **endocannabinoid system**, which plays a role in seizure control. *Lennox-Gastaut syndrome* - **Cannabidiol (Epidiolex)** is also approved for the treatment of seizures associated with **Lennox-Gastaut syndrome**, another severe and intractable childhood epilepsy. - Its efficacy in reducing seizure frequency in LGS has been demonstrated in clinical trials. *Tuberous sclerosis complex* - While not as widely established as for Dravet or Lennox-Gastaut, **cannabidiol (Epidiolex)** has shown promise and is approved in some regions for treating seizures associated with **tuberous sclerosis complex (TSC)**. - TSC is a genetic disorder causing benign tumors in multiple organs, often leading to epilepsy.

Question 753: In which of the following conditions are cannabinoids not commonly used for treatment?

A. Tuberous sclerosis
B. Rett syndrome (Correct Answer)
C. Lennox-Gastaut Syndrome
D. Dravet syndrome

Explanation: ***Rett syndrome*** - Cannabinoids are **NOT commonly used** as an established treatment for **Rett syndrome** - While some research is exploring their potential therapeutic role, they remain **investigational only** and lack FDA approval for this indication - Current management focuses on symptomatic treatment including physical therapy, anti-epileptics for seizures, and supportive care - Unlike the other conditions listed, there is **no established cannabinoid therapy** for Rett syndrome in clinical practice *Dravet syndrome* - **Cannabidiol (CBD/Epidiolex)** is **FDA-approved** and commonly used for treatment of seizures associated with **Dravet syndrome** - Demonstrates significant efficacy in reducing seizure frequency in this severe infantile-onset epilepsy - Represents a major therapeutic advance for this treatment-resistant condition *Tuberous sclerosis* - **Cannabidiol (CBD/Epidiolex)** received **FDA approval in 2018** for treatment of seizures associated with **tuberous sclerosis complex (TSC)** - Commonly used as an adjunctive therapy alongside other treatments like vigabatrin or mTOR inhibitors (everolimus) - Clinical trials demonstrated significant reduction in seizure frequency in TSC patients *Lennox-Gastaut Syndrome* - **Cannabidiol (CBD/Epidiolex)** is **FDA-approved** for seizures associated with **Lennox-Gastaut Syndrome (LGS)** - Commonly used in this severe epileptic encephalopathy characterized by multiple seizure types and developmental delay - Effective in reducing seizure burden in patients refractory to traditional anti-epileptic drugs

Question 754: A 65-year-old woman with Parkinson’s disease has been experiencing worsening tremors despite taking levodopa. Which medication can be added to her treatment regimen?

A. Phenytoin
B. Aspirin
C. Ropinirole (Correct Answer)
D. Gabapentin

Explanation: ***Ropinirole*** - **Ropinirole** is a **dopamine agonist** that directly stimulates dopamine receptors (D2 and D3) in the brain, mimicking the effects of dopamine. It is commonly used as an **adjunct to levodopa** to improve motor symptoms and reduce off-time in Parkinson's disease. - When levodopa alone is insufficient to control symptoms (as in this case), dopamine agonists like ropinirole can help to prolong the therapeutic effects and manage **motor fluctuations**, including tremors, by providing more continuous dopaminergic stimulation. - Ropinirole is FDA-approved for both **monotherapy** in early Parkinson's and as **add-on therapy** in advanced disease with motor complications. *Phenytoin* - **Phenytoin** is an **antieconvulsant** medication primarily used to treat epilepsy and certain types of seizures. - It has **no established role** in the treatment of Parkinson's disease or its associated tremors. *Aspirin* - **Aspirin** is an **NSAID** and antiplatelet agent, commonly used for pain relief, fever reduction, and cardiovascular protection. - It does **not have direct therapeutic effects** on the motor symptoms of Parkinson's disease like tremors. *Gabapentin* - **Gabapentin** is an anticonvulsant and neuropathic pain medication, often used to treat **neuropathic pain**, restless legs syndrome, and seizures. - It is **not effective** for managing the tremors or other motor symptoms of Parkinson's disease.

Question 755: Why are patients with Parkinson’s disease often treated with levodopa?

A. To increase dopamine levels in the brain (Correct Answer)
B. To decrease acetylcholine levels in the brain
C. To inhibit serotonin production
D. To block norepinephrine activity

Explanation: ***To increase dopamine levels in the brain*** - **Levodopa** is a precursor to **dopamine** and is used to replenish dopamine levels in the brain, as Parkinson's disease is characterized by the degeneration of dopaminergic neurons in the **substantia nigra**. - Since dopamine itself cannot cross the **blood-brain barrier**, levodopa is administered and then converted into dopamine within the brain, thereby alleviating motor symptoms. *To inhibit serotonin production* - **Serotonin** is a neurotransmitter involved in mood, sleep, and appetite, but its production is not the primary target in Parkinson's disease treatment. - While there can be interactions and indirect effects, levodopa's main mechanism does not involve inhibiting serotonin. *To block norepinephrine activity* - **Norepinephrine** is a neurotransmitter involved in alertness and fight-or-flight responses, and while it can be affected in Parkinson's disease, blocking its activity is not the primary goal of levodopa treatment. - Medications that block norepinephrine are typically used for conditions like anxiety or hypertension, not to treat the core symptoms of Parkinson's. *To decrease acetylcholine levels in the brain* - Decreasing **acetylcholine** levels is a strategy used for some Parkinson's symptoms, particularly tremors, using **anticholinergic drugs**. - However, this is a separate pharmacological approach and not the mechanism of action for levodopa, which focuses on increasing dopamine.

Question 756: How do benzodiazepines exert their sedative effects?

A. They enhance GABAergic transmission. (Correct Answer)
B. They increase norepinephrine levels and enhance GABA transmission.
C. They block dopamine receptors and enhance GABA transmission.
D. They inhibit acetylcholine release and enhance GABA transmission.

Explanation: ***They enhance GABAergic transmission.*** - Benzodiazepines bind to a specific site on the **GABA-A receptor**, increasing its affinity for the **neurotransmitter GABA**. - This binding leads to an increased frequency of **chloride channel opening**, hyperpolarizing the neuron and making it less excitable, which produces sedative effects. *They increase norepinephrine levels and enhance GABA transmission.* - While benzodiazepines enhance GABA transmission, they do **not primarily increase norepinephrine levels**. - Medications that increase norepinephrine levels, such as certain antidepressants, typically have stimulating rather than sedative effects. *They block dopamine receptors and enhance GABA transmission.* - While benzodiazepines enhance GABA transmission, they do **not block dopamine receptors**. - Blocking dopamine receptors is the primary mechanism of action for many **antipsychotic medications**, which have different pharmacological profiles and side effects compared to benzodiazepines. *They inhibit acetylcholine release and enhance GABA transmission.* - While benzodiazepines enhance GABA transmission, they generally do **not directly inhibit acetylcholine release**. - Muscarinic acetylcholine receptor antagonists (anticholinergics) inhibit acetylcholine and can cause sedation, but this is a distinct mechanism from benzodiazepines.

Question 757: A patient with multiple sclerosis presents with worsening spasticity. Which of the following drugs would be most appropriate for managing spasticity in this patient?

A. Ibuprofen
B. Diazepam
C. Baclofen (Correct Answer)
D. Phenytoin

Explanation: ***Baclofen*** - **Baclofen** is a **GABA-B receptor agonist** that works by inhibiting excitatory neurotransmission in the spinal cord, effectively reducing **spasticity** in conditions like multiple sclerosis. - It is a first-line treatment for managing chronic severe spasticity due to its effectiveness in muscle relaxation and pain reduction. *Ibuprofen* - **Ibuprofen** is a **non-steroidal anti-inflammatory drug (NSAID)** primarily used for pain and inflammation, and it has no direct effect on muscle spasticity. - While it might alleviate some associated musculoskeletal pain, it does not address the underlying neurological cause of **spasticity**. *Diazepam* - **Diazepam** is a **benzodiazepine** that acts as a **GABA-A receptor positive allosteric modulator**, enhancing GABAergic inhibition and leading to generalized muscle relaxation and sedation. - While it can reduce spasticity, its use is often limited due to significant **sedation**, cognitive impairment, and potential for dependence, especially in long-term management, making it a second-line agent compared to baclofen. *Phenytoin* - **Phenytoin** is an **antiepileptic drug** primarily used to treat seizures and certain neuropathic pains. - It works by blocking voltage-gated sodium channels and has no significant role in the management of **spasticity** in multiple sclerosis.

Question 758: Which of the following is considered the MOST effective first-line pharmacotherapy for tobacco cessation in non-pregnant adults based on clinical trial evidence?

A. Varenicline (Correct Answer)
B. Bupropion
C. Nicotine replacement therapy
D. Clonidine

Explanation: ***Varenicline*** - **Varenicline** has been shown in clinical trials to be the **most effective single agent** for tobacco cessation, significantly increasing abstinence rates compared to placebo and other pharmacotherapies. - Its mechanism involves **partial agonism of the α4β2 nicotinic acetylcholine receptor**, reducing cravings and withdrawal symptoms while blocking the dopamine reward pathway if nicotine is consumed. *Bupropion* - **Bupropion** is an antidepressant that also aids in smoking cessation by inhibiting the reuptake of **norepinephrine** and **dopamine**. - While effective, its efficacy in clinical trials is generally considered **lower than that of varenicline**. *Nicotine replacement therapy* - **Nicotine replacement therapy (NRT)** delivers nicotine without the harmful chemicals in tobacco, alleviating withdrawal symptoms and cravings. - Although effective and available in many forms (patches, gum, lozenges, inhalers, nasal sprays), **individual NRT products are less effective than varenicline** when used as monotherapy. *Clonidine* - **Clonidine** is an alpha-2 adrenergic agonist that can help reduce nicotine withdrawal symptoms like anxiety and restlessness. - However, its use is **limited by side effects** such as sedation and hypotension, and it is generally considered a **second-line or adjunctive treatment**, with lower efficacy than other first-line agents.

Question 759: Which drug is the specific reversal agent for vecuronium?

A. Neostigmine
B. Sugammadex (Correct Answer)
C. Edrophonium
D. Atropine

Explanation: ***Sugammadex*** - **Sugammadex** is a modified gamma-cyclodextrin that forms a tight, water-soluble complex with **rocuronium** and **vecuronium** in plasma, thereby reducing the concentration of free drug available to bind to the **nicotinic acetylcholine receptors**. - This encapsulation effectively reverses the **neuromuscular blockade** induced by these steroidal non-depolarizing muscle relaxants. *Neostigmine* - **Neostigmine** is an **acetylcholinesterase inhibitor** that increases the amount of acetylcholine at the neuromuscular junction, indirectly reversing the effects of non-depolarizing muscle relaxants. - While it can reverse some non-depolarizing agents, it is less effective and carries more **cholinergic side effects** compared to sugammadex for vecuronium reversal. *Edrophonium* - **Edrophonium** is another **acetylcholinesterase inhibitor**, but with a very short duration of action, primarily used for diagnosing myasthenia gravis, not for routine reversal of neuromuscular blockade. - Its rapid onset and brief action make it unsuitable for reversing long-acting neuromuscular blockers like vecuronium due to the risk of **recurarization**. *Atropine* - **Atropine** is an **anticholinergic drug** often given with acetylcholinesterase inhibitors like neostigmine to counteract their muscarinic side effects (e.g., bradycardia, increased secretions). - It does not directly reverse the **neuromuscular blockade** caused by vecuronium but merely manages the side effects of other reversal agents.

Question 760: What is the first-line treatment for status epilepticus?

A. Phenytoin
B. Valproic acid
C. Diazepam
D. Lorazepam (Correct Answer)

Explanation: ***Lorazepam*** - **Benzodiazepines** like lorazepam are the **first-line treatment** for status epilepticus due to their rapid onset of action and efficacy in terminating seizures. - Lorazepam is preferred over other benzodiazepines in IV form because of its **longer duration of action** and **lesser lipid solubility**, which keeps it in the central nervous system for longer. *Phenytoin* - **Phenytoin** is typically used as a **second-line agent** or as a maintenance therapy after the initial seizure has been controlled with a benzodiazepine. - It has a slower onset of action compared to benzodiazepines and is primarily used to prevent seizure recurrence. *Valproic acid* - **Valproic acid** is an **anti-epileptic drug** that can be used for status epilepticus, but it is not typically the first-line agent. - It is often considered in cases refractory to benzodiazepines or as an alternative in specific patient populations. *Diazepam* - While **diazepam** is a **benzodiazepine** used for status epilepticus, it has a **shorter duration of action** compared to lorazepam when administered intravenously. - Its rapid redistribution out of the CNS makes it less ideal for sustained seizure control compared to lorazepam in the initial management of status epilepticus.

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General Anesthetics

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Local Anesthetics

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Drugs of Abuse and Addiction

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Psychostimulants

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Hallucinogens

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CNS Stimulants and Cognitive Enhancers

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