Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology Indian Medical PG Practice Questions and MCQs

Question 731: Which of the following drugs is not used in Juvenile Myoclonic Epilepsy (JME):

A. Carbamazepine (Correct Answer)
B. Zonisamide
C. Valproate
D. Topiramate

Explanation: ***Carbamazepine*** - **Carbamazepine** is known to **exacerbate myoclonus** in patients with JME and can worsen seizures due to its mechanism of action, which can increase cortical excitability or asynchronous firing in this specific epilepsy syndrome. - Its use can **worsen seizure control** in JME, leading to more frequent or severe myoclonic jerks and generalized tonic-clonic seizures. *Zonisamide* - **Zonisamide** is a broad-spectrum antiepileptic drug that is effective in treating JME by affecting multiple pathways, including **sodium and calcium channels**, and enhancing GABAergic transmission. - It effectively **reduces myoclonic, absence, and generalized tonic-clonic seizures** typically seen in JME. *Valproate* - **Valproate** is considered a **first-line treatment** for JME due to its broad-spectrum efficacy against all seizure types associated with the syndrome (myoclonic, absence, and generalized tonic-clonic). - It works by increasing **GABA levels**, reducing neuronal excitability, and modulating sodium and T-type calcium channels. *Topiramate* - **Topiramate** is also a broad-spectrum antiepileptic drug used in JME, effective for various seizure types, including generalized tonic-clonic, myoclonic, and absence seizures. - Its mechanism involves **blocking voltage-gated sodium channels**, enhancing GABA activity, and modulating AMPA/kainate glutamate receptors.

Question 732: 72-year-old gentleman with normal renal functions presents with new onset focal seizures. Which of the following is the best drug to manage the patient?

A. Oxcarbazepine
B. Sodium valproate
C. Pregabalin
D. Levetiracetam (Correct Answer)

Explanation: ***Levetiracetam*** - **Levetiracetam** is an excellent choice for elderly patients with new-onset focal seizures due to its favorable side effect profile, **minimal drug interactions**, and lack of significant hepatic or renal metabolism, making it suitable for those with normal renal function. - It has a generally **good tolerability**, especially important in the elderly who may be on multiple medications and more sensitive to side effects. *Oxcarbazepine* - **Oxcarbazepine** can cause significant **hyponatremia**, which is a concern in elderly patients who may already be at risk due to other medications or conditions. - While effective for focal seizures, its potential for electrolyte disturbances makes it less ideal than levetiracetam in this demographic. *Sodium valproate* - **Sodium valproate** is associated with a higher risk of **cognitive side effects**, sedation, and **tremor**, which can significantly impact the quality of life in elderly patients. - It also has a potential for **hepatotoxicity** and numerous drug interactions, making it a less preferred option. *Pregabalin* - **Pregabalin** is primarily indicated for partial seizures and **neuropathic pain**, and while it can be used as an add-on therapy, it is not typically a first-line monotherapy for new-onset focal seizures. - It often causes **dizziness and somnolence**, which can increase the risk of falls in the elderly, a major concern in this age group.

Question 733: Shortest acting non benzodiazepine sedative is

A. Zaleplon (Correct Answer)
B. Eszopiclone
C. Zopiclone
D. Zolpidem

Explanation: ***Zaleplon*** - Has the shortest **half-life** (approximately 1 hour) among the non-benzodiazepine hypnotics, allowing for rapid elimination. - This quick elimination makes it ideal for patients who have difficulty **falling asleep** but do not need prolonged sedation. - Particularly useful for **middle-of-the-night** dosing due to its ultra-short duration. *Eszopiclone* - Has a half-life of about 6 hours, which is significantly longer than Zaleplon. - It's the S-enantiomer of zopiclone and is used for both **sleep onset and maintenance**. - Provides more sustained sleep throughout the night compared to Zaleplon. *Zopiclone* - Has a half-life of about 5-6 hours, which is considerably longer than Zaleplon. - It's used for the short-term treatment of **insomnia** and helps both with sleep onset and maintenance. - May cause a characteristic **bitter metallic taste** as a side effect. *Zolpidem* - Has a half-life of 2-3 hours, making it longer-acting than Zaleplon. - It's commonly prescribed for problems with **sleep initiation** and occasionally for sleep maintenance. - Available in extended-release formulations for prolonged action.

Question 734: Fastest acting non-depolarizing neuromuscular blocker currently available in clinical practice:

A. Rocuronium (Correct Answer)
B. Rapacuronium
C. Mivacurium
D. Succinylcholine

Explanation: ***Rocuronium*** - **Rocuronium** has the most rapid onset among all currently available **non-depolarizing neuromuscular blockers**, making it clinically advantageous for rapid sequence intubation (RSI) when **succinylcholine** is contraindicated [1]. - Its rapid onset is due to its relatively **low potency**, meaning that a higher dose is typically administered, which hastens receptor binding and the establishment of neuromuscular blockade [1]. *Rapacuronium* - **Rapacuronium** was developed as an ultra-short-acting agent with rapid onset, but it was withdrawn from the market due to concerns about its association with **bronchospasm** and other serious adverse effects. - Therefore, it is no longer available in clinical practice. *Mivacurium* - **Mivacurium** is an intermediate-acting non-depolarizing neuromuscular blocker, but its onset of action is significantly **slower than rocuronium** and it is rarely used for rapid intubation. - Its metabolism by **plasma cholinesterase** allows for a relatively quick recovery, but this does not translate to a rapid onset. *Succinylcholine* - **Succinylcholine** is a **depolarizing neuromuscular blocker** with the fastest onset of action of ALL neuromuscular blockers (depolarizing and non-depolarizing) [1]. - However, the question specifically asks for a **non-depolarizing** agent, and succinylcholine's mechanism of action and side effect profile are distinct from non-depolarizing agents [1].

Question 735: Which of the following is true about trigeminal neuralgia?

A. Can be treated with NSAID's
B. Is a hereditary condition
C. Carbamazepine is the drug of choice in trigeminal neuralgia. (Correct Answer)
D. Always bilateral in distribution

Explanation: ***Carbamazepine is the drug of choice in trigeminal neuralgia.*** - **Carbamazepine** is an **anticonvulsant** that is highly effective in reducing the frequency and severity of the paroxysmal pain attacks seen in trigeminal neuralgia. - Its mechanism of action in this condition is thought to involve the **blockade of voltage-gated sodium channels**, reducing neuronal excitability in the trigeminal pathway. *Can be treated with NSAID's* - **Non-steroidal anti-inflammatory drugs (NSAIDs)** are generally **ineffective** in treating the neuropathic, sharp, lancinating pain characteristic of trigeminal neuralgia. - NSAIDs primarily target inflammatory pain, which is not the underlying mechanism of trigeminal neuralgia. *Is a hereditary condition* - Trigeminal neuralgia is typically considered an **acquired condition**, often caused by **vascular compression** of the trigeminal nerve root, rather than a hereditary disorder. - While some rare genetic predispositions to neuropathic pain exist, trigeminal neuralgia itself is not generally inherited. *Always bilateral in distribution* - Trigeminal neuralgia is overwhelmingly **unilateral**, affecting only one side of the face in the distribution of the trigeminal nerve. - **Bilateral involvement** is very rare and, if present, often suggests a **secondary cause** such as multiple sclerosis or a tumor.

Question 736: All the following drugs are used for Absence seizures except -

A. Valproate
B. Ethosuximide
C. Clonazepam
D. Phenytoin (Correct Answer)

Explanation: ***Phenytoin*** - Phenytoin is primarily effective in treating **tonic-clonic seizures** and **focal seizures** by blocking voltage-gated sodium channels. - It can actually exacerbate **absence seizures** or have no therapeutic effect on them. *Valproate* - **Valproate** is a broad-spectrum antiepileptic drug effective against various seizure types, including **absence seizures**. - It works by blocking **voltage-gated sodium channels**, enhancing GABAergic transmission, and inhibiting T-type calcium channels. *Ethosuximide* - **Ethosuximide** is the **first-line drug** for treating **absence seizures** due to its selective action. - It primarily acts by blocking **T-type calcium channels** in the thalamic neurons, which are crucial for generating absence seizures. *Clonazepam* - **Clonazepam**, a benzodiazepine, is effective for treating **absence seizures** by enhancing **GABAergic inhibitory neurotransmission**. - It can be used as an **adjunct or alternative** when other drugs are not effective or tolerated, though it has more sedative side effects.

Question 737: In treatment of Parkinsonism with Levodopa dose limiting toxicity is

A. Giddiness
B. Vomiting
C. Tardive dyskinesia
D. Choreiform movements (Correct Answer)

Explanation: ***Choreiform movements*** - **Choreiform movements** (dyskinesias) are a common dose-limiting toxicity of **levodopa** in Parkinson's disease, occurring as the cumulative dose increases over time. - These involuntary, dance-like movements are largely due to **pulsatile stimulation** of dopamine receptors, eventually leading to their hypersensitivity. *Giddiness* - **Giddiness** or **orthostatic hypotension** can occur with levodopa, especially early in treatment, but it is typically managed by dose titration or adjunct therapies rather than being a primary dose-limiting toxicity that necessitates stopping the drug. - While it can be a side effect, it rarely limits the continuation of levodopa therapy in the long term as much as dyskinesias do. *Vomiting* - **Nausea and vomiting** are common initial side effects of levodopa, particularly without a **decarboxylase inhibitor** like carbidopa. - These symptoms are usually managed by administering levodopa with food or by adding carbidopa, and are not typically the primary factor limiting chronic high-dose therapy. *Tardive dyskinesia* - **Tardive dyskinesia** is primarily associated with **long-term use of dopamine receptor blockers** (e.g., antipsychotics), not typically with levodopa. - While levodopa can cause dyskinesias, the term "tardive dyskinesia" is specifically reserved for neuroleptic-induced movement disorders.

Question 738: Which drug is used for Myasthenia Gravis testing?

A. Acetylcholine
B. Physostigmine
C. Adrenaline
D. Edrophonium (Correct Answer)

Explanation: ***Edrophonium*** - **Edrophonium** is an **ultrashort-acting acetylcholinesterase inhibitor** that temporarily increases acetylcholine at the neuromuscular junction, improving muscle weakness in myasthenia gravis patients. - The **Tensilon test** (using edrophonium) is performed by injecting the drug and observing for rapid, transient improvement in muscle strength, such as in eyelid ptosis or extraocular muscle weakness. *Acetylcholine* - **Acetylcholine** is the neurotransmitter responsible for muscle contraction; however, direct administration is not used for diagnosing myasthenia gravis. - In myasthenia gravis, the problem is with **acetylcholine receptors** being blocked or destroyed, not a lack of acetylcholine production itself. *Phycostigmine* - **Physostigmine** is an **acetylcholinesterase inhibitor** but has a longer duration of action and crosses the blood-brain barrier, making it less suitable for rapid diagnostic testing of myasthenia gravis compared to edrophonium. - It is sometimes used for treating **anticholinergic toxicity**, not for diagnosing myasthenia gravis. *Adrenaline* - **Adrenaline (epinephrine)** is a **catecholamine** and a neurotransmitter primarily involved in the fight-or-flight response, mainly acting on adrenergic receptors. - It has no direct role in the *diagnosis* or *pathophysiology* of myasthenia gravis, which involves cholinergic transmission.

Question 739: Drug of choice in treatment of partial complex seizures

A. Sodium valproate
B. Phenytoin
C. Carbamazepine (Correct Answer)
D. Ethosuximide

Explanation: ***Carbamazepine*** - **Carbamazepine** is a **first-line agent** for **focal (partial) onset seizures**, including complex partial seizures, due to its efficacy in stabilizing neuronal membranes. - It works by blocking **voltage-gated sodium channels**, reducing abnormal electrical activity in the brain. *Sodium valproate* - **Sodium valproate** is a **broad-spectrum anticonvulsant** effective against both **generalized and focal seizures**, but it is generally considered **first-line for generalized seizures**, especially absence and myoclonic. - While it can be used for partial seizures, carbamazepine or oxcarbazepine are usually preferred as initial therapy for focal seizures. *Phenytoin* - **Phenytoin** is an effective anticonvulsant for **focal (partial) and generalized tonic-clonic seizures**, blocking sodium channels to prevent seizure propagation. - However, its use is limited by a **narrow therapeutic index**, significant drug interactions, and dose-related side effects such as **gingival hyperplasia**, nystagmus, and hirsutism. *Ethosuximide* - **Ethosuximide** is the **drug of choice** specifically for **absence seizures** (pyknolepsy) by inhibiting T-type calcium channels in the thalamus. - It has **no significant efficacy** against partial complex seizures or generalized tonic-clonic seizures.

Question 740: Antagonist of benzodiazepine is?

A. Buspirone
B. Zolpidem
C. Ramelteon
D. Flumazenil (Correct Answer)

Explanation: ***Flumazenil*** - **Flumazenil** is a competitive antagonist at the **GABA-A receptor**, where benzodiazepines exert their effects. - It is used to reverse the sedative and respiratory depressant effects of **benzodiazepine overdose** or to aid in recovery from general anesthesia induced with benzodiazepines. *Buspirone* - **Buspirone** is an anxiolytic agent that acts primarily as a **selective serotonin 5-HT1A receptor partial agonist**, with no direct benzodiazepine receptor activity. - It is used for generalized anxiety disorder but does not reverse benzodiazepine effects. *Zolpidem* - **Zolpidem** is a **non-benzodiazepine hypnotic** (Z-drug) that selectively agonizes the **alpha-1 subunit of the GABA-A receptor**, exhibiting hypnotic effects. - While it acts on the GABA-A receptor, it is an agonist, not an antagonist, and thus exaggerates rather than reverses benzodiazepine-like effects. *Ramelteon* - **Ramelteon** is a **melatonin receptor agonist** that acts on MT1 and MT2 receptors in the suprachiasmatic nucleus. - It helps regulate the sleep-wake cycle and is used for insomnia, but it has no interaction with the benzodiazepine receptor.

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