Central Nervous System Pharmacology Practice Questions

Q: Secobarbital is what type of barbiturate?

Short acting barbiturate. ***Short acting barbiturate*** - **Secobarbital** is classified as a short-acting barbiturate, with an onset of action of 15-30 minutes and a duration of 3-6 hours. - Due to its rapid onset and relatively short duration, it has been used as a **sedative-hypnotic** for inducing sleep. *Long acting barbiturate* - **Long-acting barbiturates** like **phenobarbital** have a prolonged duration of action, typically lasting 10-16 hours. - They are primarily used as **antiepileptics** due to their sustained effects. *Intermediate acting barbiturate* - **Intermediate-acting barbiturates** such as **amobarbital** have durations of action between 6-10 hours. - They were historically used for insomnia, but their use has declined due to safer alternatives. *Ultra short acting barbiturate* - **Ultra-short-acting barbiturates** like **thiopental** have an extremely rapid onset (seconds) and very short duration (minutes). - They are mainly used for **induction of anesthesia** due to their quick action and rapid redistribution.

Q: Muscle rigidity due to opioids is primarily caused by their effect on which receptor?

mu. ***mu*** - Opioids, by activating **mu-opioid receptors**, particularly in the **brainstem** and **spinal cord**, can cause a phenomenon known as "wooden chest syndrome" or muscle rigidity. - This effect results from increased dopamine turnover in the **nigrostriatal pathway** and is pronounced with rapid intravenous administration of potent opioids like **fentanyl**. *kappa* - **Kappa-opioid receptors** are primarily associated with effects like **dysphoria** [1], **sedation**, and **diuresis**. - While they contribute to some opioid effects, they are not the primary mediators of **muscle rigidity**. *sigma* - The **sigma receptor** is not considered a classical opioid receptor and is not directly involved in the analgesic effects of opioids. - Activation of **sigma receptors** is associated with effects like **dysphoria**, hallucinations, and motor incoordination, but not the specific muscle rigidity caused by opioids. *delta* - **Delta-opioid receptors** play a role in **analgesia** [1], **mood regulation**, and **epileptic seizures**. - They are not directly implicated in the mechanism of **opioid-induced muscle rigidity**.

Q: A patient has frequent migraine attacks. Which of the following drugs is recommended for prophylaxis?

Propranolol. **Correct: Propranolol** - Propranolol is a **beta-blocker** commonly used for **migraine prophylaxis** [1] - It is **FDA-approved** and considered a **first-line agent** for preventing migraine attacks [1] - It works by reducing the frequency and severity of migraine attacks through its effects on vascular tone and neuronal excitability [1] *Incorrect: Pindolol* - Pindolol is a beta-blocker but is **less effective for migraine prophylaxis** compared to propranolol - It has **intrinsic sympathomimetic activity (ISA)**, which reduces its efficacy in preventing migraines - Not a preferred agent for migraine prevention *Incorrect: Ergotamine* - Ergotamine is used for **acute treatment** of migraine attacks, **not for prophylaxis** [2] - It works by constricting blood vessels and is a vasoconstrictor [2] - **Not suitable for daily preventive use** due to potential side effects, risk of ergotism, and medication overuse headaches (rebound headaches) [2] *Incorrect: None of the options* - This option is incorrect because **propranolol** is a well-established and recommended drug for migraine prophylaxis according to current guidelines

Q: Entacapone acts by inhibiting which of the following enzyme?

COMT. ***Correct: COMT*** - **Entacapone** is a selective, reversible **COMT (Catechol-O-Methyltransferase) inhibitor** [1], [2] - Acts **peripherally** (does not cross blood-brain barrier) [1], [2] - Used as **adjunct to levodopa/carbidopa** in Parkinson's disease [2] - **Mechanism:** Prevents peripheral conversion of levodopa to 3-O-methyldopa, thereby **increasing levodopa bioavailability** and prolonging its duration of action [1], [2] - Reduces "wearing-off" phenomenon in Parkinson's patients [2] *Incorrect: MAO-A* - Monoamine oxidase-A metabolizes dopamine, norepinephrine, and serotonin - **Moclobemide** is a reversible MAO-A inhibitor (antidepressant) - Not the mechanism of entacapone *Incorrect: MAO-B* - Monoamine oxidase-B preferentially metabolizes dopamine in the CNS - **Selegiline and rasagiline** are MAO-B inhibitors used in Parkinson's disease [2] - These work centrally, unlike entacapone which is peripheral [2] *Incorrect: Decarboxylase* - DOPA decarboxylase converts levodopa to dopamine - **Carbidopa and benserazide** are decarboxylase inhibitors (given with levodopa) [2] - Entacapone works downstream by inhibiting COMT, not decarboxylase

Q: The mechanism of action of haloperidol is the blockade of

Dopamine receptor. ***Dopamine receptor*** - Haloperidol is a **first-generation antipsychotic** that primarily acts as a potent **D2 dopamine receptor antagonist**. - Its therapeutic effects in treating psychosis are largely due to blocking **dopamine D2 receptors** in the mesolimbic pathway, which helps reduce positive symptoms like hallucinations and delusions. *Serotonin receptor* - While some atypical (second-generation) antipsychotics block serotonin receptors (e.g., 5-HT2A), **haloperidol's primary mechanism of action is not serotonin receptor blockade**. - Serotonin receptor antagonism is more associated with the mechanism of action of newer antipsychotics, which also exhibit D2 antagonism but with a different receptor profile. *GABA receptor* - **Haloperidol does not primarily act on GABA receptors**; drugs like benzodiazepines are known for their GABAergic effects. - GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the brain, and drugs targeting its receptors are typically anxiolytics or sedatives. *Adrenergic receptor* - Although haloperidol can have some weak alpha-1 adrenergic receptor blocking activity, this is a **secondary effect** and not its primary mechanism of action. - Its antipsychotic efficacy is overwhelmingly attributed to its potent **dopamine receptor blockade**.

Q: Symptomatic treatment is only required in withdrawal syndrome caused by:

Cannabis. ***Cannabis*** - **Cannabis withdrawal syndrome** is generally mild and non-life-threatening, **requiring only symptomatic management** for symptoms such as irritability, anxiety, sleep disturbances, and cravings. - Unlike withdrawal from opioids or alcohol, cannabis withdrawal does not present with severe physiological complications, seizures, or significant psychological distress requiring pharmacotherapy. - **Supportive care alone is sufficient** with reassurance, hydration, and rest. *Morphine* - **Opioid withdrawal** (e.g., from morphine) can be very distressing and painful, involving severe gastrointestinal symptoms, myalgia, and intense cravings. - **Requires pharmacological intervention** with medications like **methadone**, **buprenorphine**, or **clonidine** for symptom control and to prevent relapse. - Not merely symptomatic treatment. *Alcohol* - **Alcohol withdrawal syndrome** can be severe and life-threatening, potentially progressing to **delirium tremens** and seizures. - **Necessitates pharmacological treatment** with **benzodiazepines** (e.g., lorazepam, diazepam) to prevent serious complications. - Symptomatic treatment alone is inadequate and dangerous. *Cocaine* - **Cocaine withdrawal** is characterized by **dysphoria**, fatigue, hypersomnia, and intense cravings with high relapse risk. - While primarily managed with supportive care, **severe cases often require pharmacological intervention** for depression (antidepressants) and intense cravings. - Unlike cannabis, the psychological severity often necessitates more than just symptomatic management.

Q: Which of the following drugs is primarily used for the treatment of Parkinson's disease?

Levodopa. ***Levodopa*** - Levodopa is a **dopamine precursor** that crosses the blood-brain barrier and is converted to dopamine in the brain, replacing the depleted dopamine in Parkinson's disease [1], [2]. - It is considered the **most effective drug** for managing the motor symptoms of Parkinson's disease, particularly in the early and moderate stages [2], [4]. *Mazindol* - **Mazindol** is an appetite suppressant used for obesity and acts primarily as a norepinephrine-dopamine reuptake inhibitor. - It is **not indicated** for the treatment of Parkinson's disease. *Benserazide* - **Benserazide** is a **peripheral DOPA decarboxylase inhibitor** that does not cross the blood-brain barrier [1]. - It is used in combination with levodopa (e.g., in co-beneldopa) to prevent the peripheral metabolism of levodopa, increasing its availability to the brain, but it is **not used alone** to treat Parkinson's disease [1]. *Bromocriptine* - **Bromocriptine** is a **dopamine agonist** that directly stimulates dopamine receptors in the brain [3]. - While used in Parkinson's disease, it is generally considered a **second-line treatment** or used as an adjunct to levodopa, and not the primary drug [3].

Q: Which of the following is a non-cholinergic agent?

Memantine. ***Memantine*** - Memantine is an **NMDA receptor antagonist** and works by blocking the effects of excessive **glutamate**, a neurotransmitter that can contribute to neuronal damage in Alzheimer's disease. - Unlike the other options, it does not directly interfere with the **acetylcholine** system but rather modulates glutamatergic neurotransmission. *Galantamine* - Galantamine is an **acetylcholinesterase inhibitor** and an allosteric modulator of nicotinic acetylcholine receptors. - It increases the availability of **acetylcholine** in the synaptic cleft, making it a cholinergic agent. *Donepezil* - Donepezil is a **reversible acetylcholinesterase inhibitor** used in the treatment of Alzheimer's disease. - Its mechanism of action involves increasing the concentration of **acetylcholine** in the brain, thus it is a cholinergic agent. *Tacrine* - Tacrine was one of the first **acetylcholinesterase inhibitors** approved for Alzheimer's disease. - It works by preventing the breakdown of **acetylcholine**, thereby increasing its levels in the brain and is considered a cholinergic agent.

Q: What is the drug used in uncomplicated alcohol withdrawal?

Diazepam. ***Diazepam***- **Benzodiazepines** like diazepam are the cornerstone of treatment for alcohol withdrawal due to their ability to mitigate severe symptoms such as **seizures** and **delirium tremens** [1].- Diazepam, with its **long half-life**, provides a sustained therapeutic effect, helping to prevent symptom re-emergence.*Clonidine*- While clonidine can alleviate **autonomic symptoms** like elevated heart rate and blood pressure, it does not prevent **seizures or delirium**, which are critical concerns in alcohol withdrawal.- It is often used as an **adjunct** but not as monotherapy for uncomplicated withdrawal.*Methadone*- Methadone is an **opioid agonist** primarily used in the treatment of **opioid addiction**, not alcohol withdrawal.- It has no role in directly managing symptoms of alcohol withdrawal and could be dangerous if misused in this context.*Propranolol*- Propranolol is a **beta-blocker** that can help reduce some **autonomic symptoms** such as **tremors** and **tachycardia**.- Similar to clonidine, it does not address the risk of **seizures** or **delirium tremens**, making it unsuitable as a primary treatment.

Q: Administration of which of the following will reverse respiratory depression caused by opioids?

Naloxone. ***Naloxone*** - **Naloxone** is a pure **opioid receptor antagonist** that rapidly reverses all effects of opioid overdose, including respiratory depression - It has high affinity for **mu-opioid receptors**, which mediate both respiratory depression and analgesia - Naloxone is the **gold standard antidote** for opioid overdose and life-threatening respiratory depression - It reverses opioid effects within 1-2 minutes when given intravenously *Kappa receptor blocker* - **Kappa receptors** primarily mediate dysphoria, sedation, and some analgesia - The life-threatening **respiratory depression** from opioid overdose is primarily mediated by **mu receptors**, not kappa receptors - Selective kappa blockade would not effectively reverse mu-opioid induced respiratory depression *Delta receptor blocker* - **Delta opioid receptors** are primarily involved in modulating pain perception and emotional responses - They have minimal direct involvement in **respiratory depression** compared to mu receptors - Blocking delta receptors would not effectively counteract respiratory depression induced by **mu-opioid agonists** like morphine, fentanyl, or heroin *Adrenergic receptor stimulator* - **Adrenergic stimulators** (e.g., epinephrine) act on the sympathetic nervous system and may cause bronchodilation - They do not reverse the **central mechanism** of opioid-induced respiratory depression, which occurs at the brainstem respiratory centers via opioid receptors - While they might provide some cardiovascular support, they do not address the underlying **CNS depression** and are not appropriate antidotes for opioid toxicity

Question 1

Secobarbital is what type of barbiturate?

Accepted Answer

Short acting barbiturate

Answer

Long acting barbiturate

Answer

Intermediate acting barbiturate

Answer

Ultra short acting barbiturate

Question 2

Muscle rigidity due to opioids is primarily caused by their effect on which receptor?

Accepted Answer

mu

Answer

kappa

Answer

sigma

Answer

delta

Question 3

A patient has frequent migraine attacks. Which of the following drugs is recommended for prophylaxis?

Accepted Answer

Propranolol

Answer

None of the options

Answer

Pindolol

Answer

Ergotamine

Question 4

Entacapone acts by inhibiting which of the following enzyme?

Accepted Answer

COMT

Answer

MAO-A

Answer

MAO-B

Answer

Decarboxylase

Question 5

The mechanism of action of haloperidol is the blockade of

Accepted Answer

Dopamine receptor

Answer

Serotonin receptor

Answer

GABA receptor

Answer

Adrenergic receptor

Question 6

Symptomatic treatment is only required in withdrawal syndrome caused by:

Accepted Answer

Cannabis

Answer

Alcohol

Answer

Cocaine

Answer

Morphine

Question 7

Which of the following drugs is primarily used for the treatment of Parkinson's disease?

Accepted Answer

Levodopa

Answer

Mazindol

Answer

Benserazide

Answer

Bromocriptine

Question 8

Which of the following is a non-cholinergic agent?

Accepted Answer

Memantine

Answer

Galantamine

Answer

Donepezil

Answer

Tacrine

Question 9

What is the drug used in uncomplicated alcohol withdrawal?

Accepted Answer

Diazepam

Answer

Clonidine

Answer

Methadone

Answer

Propranolol

Question 10

Administration of which of the following will reverse respiratory depression caused by opioids?

Accepted Answer

Naloxone

Answer

Kappa receptor blocker

Answer

Delta receptor blocker

Answer

Adrenergic receptor stimulator

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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