Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology Indian Medical PG Practice Questions and MCQs

Question 861: Which drug is commonly used to mitigate the side effects of haloperidol?

A. Clozapine
B. Imipramine
C. Benztropine (Correct Answer)
D. Haloperidol

Explanation: ***Correct Option C: Benztropine*** - **Benztropine** is an **anticholinergic medication** commonly used to treat **extrapyramidal symptoms (EPS)** induced by antipsychotics like haloperidol - EPS, such as **dystonia**, **akathisia**, and **parkinsonism**, occur due to dopaminergic blockade in the nigrostriatal pathway - Benztropine works by blocking muscarinic receptors, helping to restore the dopamine-acetylcholine balance in the basal ganglia *Incorrect Option A: Clozapine* - **Clozapine** is an **atypical antipsychotic** known for its effectiveness in **treatment-resistant schizophrenia** and a lower risk of EPS compared to typical antipsychotics - However, it is not used to mitigate existing side effects of other antipsychotics due to its unique side effect profile, including agranulocytosis and myocarditis - Clozapine is a therapeutic alternative, not a treatment for EPS *Incorrect Option B: Imipramine* - **Imipramine** is a **tricyclic antidepressant (TCA)** primarily used to treat **depression** and **anxiety disorders** - It does not have properties that would mitigate the extrapyramidal side effects induced by antipsychotics - TCAs have anticholinergic properties but are not used for EPS management *Incorrect Option D: Haloperidol* - **Haloperidol** is a **typical antipsychotic** itself, and it is the drug whose side effects (e.g., EPS) are being mitigated - Administering more haloperidol would exacerbate, not mitigate, its side effects - This is the causative agent, not the treatment

Question 862: Antiviral drug amantadine is approved for treating which of the following conditions?

A. Depression
B. Alzheimer's disease
C. Parkinsonism (Correct Answer)
D. Schizophrenia

Explanation: ***Parkinsonism*** - **Amantadine** is an **antiviral agent** that also has **anti-Parkinsonian effects**, particularly useful for treating **dyskinesias** associated with long-term levodopa therapy. - It acts by influencing **dopaminergic neurotransmission** and has **NMDA receptor antagonist** properties. *Schizophrenia* - Schizophrenia is primarily treated with **antipsychotic medications** that target **dopamine** and **serotonin receptors**. - **Amantadine** is not indicated for the treatment of psychosis or other symptoms of schizophrenia. *Depression* - Depression is typically managed with **antidepressants** that modulate **serotonin**, **norepinephrine**, or **dopamine** levels. - **Amantadine** does not have established efficacy as an antidepressant drug. *Alzheimer's disease* - Treatment for Alzheimer's disease often involves **cholinesterase inhibitors** and **NMDA receptor antagonists** like memantine for cognitive symptoms. - While amantadine is an NMDA receptor antagonist, it is **not approved** or commonly used for the primary treatment of Alzheimer's disease.

Question 863: The following symptoms may be seen in opium withdrawal:

A. Tremors
B. Constipation
C. Lacrimation (Correct Answer)
D. Dry nose and mouth

Explanation: ***Lacrimation*** - Opioid withdrawal is characterized by **autonomic hyperactivity**, leading to symptoms like **lacrimation** (tearing), rhinorrhea (runny nose), and piloerection. - This is a rebound effect from the chronic opioid suppression of the parasympathetic nervous system. *Tremors* - While tremors can occur in various withdrawal syndromes, they are more characteristic of **alcohol** or **benzodiazepine withdrawal**, which involve GABAergic systems. - Opioid withdrawal can cause muscle aches and spasms, but **significant, sustained tremors** are not a primary diagnostic criterion. *Dry nose and mouth* - **Dry mouth** is a common side effect of opioid use, due to their anticholinergic effects, but during **withdrawal**, patients experience increased secretions like rhinorrhea and **lacrimation**. - **Dry nose** is also contrary to the typical presentation of opioid withdrawal, which involves a **runny nose**. *Constipation* - **Constipation** is a well-known side effect of chronic opioid use due to reduced gut motility. - During withdrawal, patients typically experience **diarrhea** and abdominal cramping, as gut motility returns and often becomes hyperactive.

Question 864: Which of the following drugs is not effective in the treatment of trigeminal neuralgia?

A. Phenytoin sodium
B. Carbamazepine
C. Baclofen
D. Acetaminophen (Correct Answer)

Explanation: ***Acetaminophen*** - **Acetaminophen** is a common **analgesic** and antipyretic but lacks the direct effect on neuronal hyperexcitability required for treating **neuropathic pain** conditions like trigeminal neuralgia. - Its mechanism of action primarily involves inhibiting prostaglandin synthesis peripherally and centrally, which is insufficient for managing the sharp, stabbing pain of **trigeminal neuralgia**. *Carbamazepine* - **Carbamazepine** is considered the **first-line treatment** for trigeminal neuralgia due to its efficacy in stabilizing hyperexcitable nerve membranes. - It works by blocking **voltage-gated sodium channels**, thereby reducing the firing of trigeminal nerve fibers. *Phenytoin sodium* - **Phenytoin** is an **antiepileptic drug** that can be used as a second-line or adjunctive treatment for trigeminal neuralgia. - Similar to carbamazepine, it acts by **inhibiting voltage-gated sodium channels**, thereby preventing repetitive firing of action potentials. *Baclofen* - **Baclofen** is a **GABA-B receptor agonist** that can be used in combination with carbamazepine or as an alternative for patients who do not respond to or tolerate carbamazepine. - It helps reduce the intensity and frequency of pain by **inhibiting excitatory neurotransmitter release** in the brainstem trigeminal nucleus.

Question 865: Which of the following statements is FALSE regarding drugs in the treatment of Parkinsonism?

A. Levodopa is effective in reducing tremors
B. Amantadine causes ankle edema
C. Anti-muscarinic agents are effective in drug-induced Parkinsonism
D. Amantadine is more effective than levodopa (Correct Answer)

Explanation: ***Amantadine is more effective than levodopa*** - This statement is **false** because **levodopa** is considered the **gold standard** and most effective treatment for symptomatic Parkinsonism, especially for bradykinesia and rigidity [1, 2]. - While amantadine can be helpful for dyskinesias and offers modest symptomatic relief, its efficacy is significantly **less than levodopa** [1]. *Amantadine causes ankle edema* - This statement is **true**. **Amantadine** is known to cause **peripheral edema**, particularly in the ankles and feet, as a common side effect [1]. - This adverse effect can be managed by reducing the dose or discontinuing the drug if bothersome. *Levodopa is effective in reducing tremors* - This statement is **true**, though with an important caveat. **Levodopa** does reduce tremor in Parkinson's disease, but it is **less effective for tremor** compared to its dramatic effects on bradykinesia and rigidity [1]. - Among parkinsonian symptoms, **tremor responds least well to levodopa** and may require additional agents like anticholinergics or propranolol for optimal control. - Nevertheless, levodopa does provide tremor reduction in most patients, making this statement true overall. *Anti-muscarinic agents are effective in drug-induced Parkinsonism* - This statement is **true**. **Anticholinergic (anti-muscarinic) agents** like benztropine and trihexyphenidyl are often used to treat **drug-induced Parkinsonism**, particularly symptoms like tremor and dystonia [1, 2]. - This form of Parkinsonism is typically caused by dopamine receptor blocking drugs (antipsychotics), making anticholinergics effective by rebalancing cholinergic overactivity.

Question 866: Which one of the following drugs is not a long-acting neuromuscular blocking agent?

A. Pancuronium
B. Doxacurium
C. Mivacurium (Correct Answer)
D. Pipecuronium

Explanation: ***Mivacurium*** - Mivacurium is an **intermediate-duration neuromuscular blocking agent**, typically lasting 15-20 minutes. - Its short duration of action is due to its rapid hydrolysis by **plasma cholinesterase**. *Doxacurium* - Doxacurium is classified as a **long-acting neuromuscular blocking agent**, with effects lasting 90-120 minutes. - It works by competitively blocking the action of **acetylcholine** at the neuromuscular junction. *Pancuronium* - Pancuronium is a **long-acting neuromuscular blocking agent**, with a duration of action of 90-120 minutes. - It is known for its vagolytic effect, which can lead to **tachycardia**. *Pipecuronium* - Pipecuronium is a **long-acting neuromuscular blocking agent**, similar to pancuronium, with a duration of action around 90-120 minutes. - It is an aminosteroid derivative used to produce **skeletal muscle relaxation** during surgery or mechanical ventilation.

Question 867: All 5-HT receptors are heptahelical serpentine receptors EXCEPT:

A. 5-HT1
B. 5-HT3 (Correct Answer)
C. 5-HT4
D. 5-HT2

Explanation: ***5-HT3*** - The **5-HT3 receptor** is unique among serotonin receptors because it is a **ligand-gated ion channel**, not a G protein-coupled receptor [2]. - Its activation directly results in rapid depolarization due to the influx of **sodium ions**, unlike the slower, second-messenger mediated responses of other 5-HT receptors [2].*5-HT1* - The **5-HT1 receptor** family (1A, 1B, 1D, 1E, 1F) are all **heptahelical G protein-coupled receptors** [1, 2]. - They are primarily coupled to **inhibitory G proteins (Gi/Go)**, leading to a decrease in cAMP levels.*5-HT4* - The **5-HT4 receptor** is a **heptahelical G protein-coupled receptor** [1, 2]. - It is coupled to **stimulatory G proteins (Gs)**, leading to an increase in cAMP levels.*5-HT2* - The **5-HT2 receptor** family (2A, 2B, 2C) are all **heptahelical G protein-coupled receptors** [1, 2]. - They are predominantly coupled to **Gq proteins**, leading to the activation of phospholipase C and increased intracellular calcium.

Question 868: Which of the following drugs is the most commonly prescribed first-line treatment for Alzheimer's disease?

A. Donepezil (Correct Answer)
B. Rivastigmine
C. Galantamine
D. Memantine

Explanation: ***Donepezil*** - **Donepezil** is a **centrally acting, reversible acetylcholinesterase inhibitor** and is widely considered the **first-line treatment** for mild to moderate Alzheimer's disease due to its efficacy and once-daily dosing. - It works by increasing the concentration of **acetylcholine** in the synaptic cleft, thereby enhancing cholinergic transmission in the brain. *Rivastigmine* - **Rivastigmine** is also an **acetylcholinesterase inhibitor**, available in oral and transdermal patch formulations, and is used for mild to moderate Alzheimer's. - While effective, it is often considered a **second-line** or alternative agent due to potential for more gastrointestinal side effects compared to donepezil. *Galantamine* - **Galantamine** is another **acetylcholinesterase inhibitor** with an additional mechanism of action as an **allosteric potentiator of nicotinic acetylcholine receptors**. - It is effective in mild to moderate Alzheimer's but is not typically the very first choice given the established prevalence and convenience of donepezil. *Memantine* - **Memantine** is an **NMDA receptor antagonist** and works by blocking the effects of excessive **glutamate**, which is thought to contribute to neurodegeneration in Alzheimer's. - It is generally prescribed for **moderate to severe Alzheimer's disease** and is not considered a first-line treatment for early stages.

Question 869: Which of the following is a short-acting benzodiazepine?

A. Midazolam (Correct Answer)
B. Lorazepam
C. Diazepam
D. Temazepam

Explanation: ***Midazolam*** - **Midazolam** is a **short-acting benzodiazepine** with a rapid onset and short duration of action, mainly due to its high lipid solubility and rapid metabolism. - It is often used for **premedication**, **sedation** for procedures, and induction of **anesthesia**. *Lorazepam* - **Lorazepam** is an **intermediate-acting benzodiazepine** with a half-life of 10-20 hours. - It is commonly used for **anxiety**, **insomnia**, and *status epilepticus*, but its duration of action is longer than truly short-acting agents. *Diazepam* - **Diazepam** is a **long-acting benzodiazepine** with a half-life ranging from 20 to 100 hours, largely due to its active metabolites, such as **nordiazepam**. - It is used for conditions requiring sustained effects, such as **chronic anxiety**, **muscle spasms**, and **alcohol withdrawal**. *Temazepam* - **Temazepam** is an **intermediate-acting benzodiazepine** with a half-life of 8-20 hours. - It is primarily prescribed for **insomnia** due to its relatively quick onset and moderate duration of action, which is not as short as midazolam.

Question 870: Which of the following drugs can be used as a transdermal patch for the treatment of Parkinson's disease?

A. Rotigotine (Correct Answer)
B. Apomorphine
C. Levodopa
D. Selegiline

Explanation: ***Rotigotine*** - **Rotigotine** is a **dopamine agonist** that is formulated as a **transdermal patch** for continuous delivery, improving compliance and reducing "off" times in Parkinson's disease. - The patch provides steady drug levels, minimizing motor fluctuations often seen with oral medications. *Levodopa* - Levodopa is the **most effective drug** for Parkinson's, but it's administered **orally** and has a short half-life, requiring frequent dosing. - While it can be combined with carbidopa/benserazide to prevent peripheral conversion, it is not available as a transdermal patch. *Apomorphine* - Apomorphine is a **potent dopamine agonist** used for rapid relief of "off" episodes; however, it is administered via **subcutaneous injection**. - It is not available in a transdermal patch formulation due to its chemical characteristics and rapid action. *Selegiline* - **Selegiline** is a **MAO-B inhibitor** that slows the breakdown of dopamine and is used as an adjunct in Parkinson's, and is available in **oral** and **sublingual forms**. - While it has transdermal formulations for depression (e.g., Emsam), it is not used as a patch for Parkinson's disease treatment.

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