Central Nervous System Pharmacology Practice Questions

Q: Which drug is given in the pain due to diabetic neuropathy?

Gabapentin. ***Gabapentin*** - **Gabapentin** is a first-line agent often prescribed for neuropathic pain, including that caused by **diabetic neuropathy**. - It works by modulating voltage-gated **calcium channels**, reducing neurotransmitter release in the pain pathways. *Lamotrigine* - While an antiepileptic drug, **lamotrigine** is primarily used for **epilepsy** and **bipolar disorder**. - It is not a first-line treatment for **diabetic neuropathic pain**. *Na valproate* - **Sodium valproate** is an anticonvulsant and mood stabilizer, mainly used for epilepsy, **bipolar disorder**, and **migraine prophylaxis**. - It is not typically recommended for the management of **diabetic neuropathic pain**. *Morphine* - **Morphine** is a strong opioid analgesic used for severe acute or chronic pain. - While it can alleviate pain, it is generally considered a **second-line or third-line agent** for **neuropathic pain** due to risks of dependence and side effects.

Q: Which of the following is not true about benzodiazepines?

REM, and Stage 3 and 4 sleep is increased. **REM, and Stage 3 and 4 sleep is increased** - Benzodiazepines actually **decrease REM sleep** and **slow-wave sleep** (Stages 3 and 4) while increasing Stage 2 sleep. - This alteration in sleep architecture contributes to less restorative sleep despite inducing sedation. *Can produce ataxia* - Benzodiazepines can cause **ataxia**, especially at higher doses, due to their depressant effects on the **cerebellum** and motor coordination centers. - This side effect is a common concern, particularly in older adults, increasing the risk of falls. *Has GABA facilitatory but no GABA mimetic action* - Benzodiazepines **facilitate the action of GABA** by increasing the *frequency* of chloride channel opening, leading to enhanced inhibitory neurotransmission. - They do not directly activate GABA receptors in the absence of GABA, meaning they have no direct **GABA mimetic action**. *Produces muscle relaxation by action on spinal cord* - Benzodiazepines exert their **muscle relaxant effects** primarily by enhancing *GABAergic inhibition* in the **spinal cord** and **brainstem**. - This leads to a reduction in skeletal muscle tone and can be beneficial in treating muscle spasms.

Q: Which of the following is true about barbiturates?

Shows GABA facilitatory action. ***Shows GABA facilitatory action*** - Barbiturates enhance the effect of **GABA** (gamma-aminobutyric acid), the primary inhibitory neurotransmitter in the central nervous system, by increasing the **duration** of chloride channel opening. - This facilitatory action leads to **hyperpolarization** of neurons, making them less excitable and resulting in CNS depression. - This is the **primary mechanism** of action of barbiturates at therapeutic doses. *Enhances GABAergic activity by mimicking GABA's effects* - While barbiturates enhance GABAergic activity, they do not **mimic GABA's effects** in the same direct way that full agonists do. - Instead of acting as direct agonists, barbiturates **allosterically modulate** the GABA A receptor, increasing the receptor's affinity for GABA and prolonging the opening time of the associated chloride channel. *Limbic system is most sensitive to the depressive action of barbiturates to CNS* - The **reticular activating system (RAS)** in the brainstem, which plays a crucial role in regulating wakefulness and arousal, is generally considered the most sensitive area to the depressive effects of barbiturates. - While the limbic system is affected, its sensitivity is not uniquely highest compared to other CNS regions like the RAS, which is critical for the sedative and hypnotic effects observed. *Primarily acts by blocking voltage gated Na+ and K+ channels* - This is **incorrect**. The primary mechanism of barbiturates is through **GABA A receptor modulation**, not by blocking voltage-gated ion channels. - While barbiturates can have non-specific membrane effects on voltage-gated channels at very high (toxic) concentrations, this is not their primary or therapeutic mechanism of action.

Q: Which of the following is used for the patient on antiparkinsonian medication levodopa + carbidopa, but patient showing marked on-off effect?

Selegiline. ***Selegiline*** - **Selegiline** is a **MAO-B inhibitor** that slows the breakdown of dopamine in the brain, thus extending the therapeutic effect of **levodopa** and reducing motor fluctuations including "on-off" phenomena. - It works by inhibiting the enzyme monoamine oxidase type B, which metabolizes dopamine, thereby preserving both endogenous and levodopa-derived dopamine for more sustained dopaminergic stimulation. - **MAO-B inhibitors** are established adjuncts to levodopa therapy for managing motor complications and reducing "off" time. *Bromocriptine* - **Bromocriptine** is a **dopamine agonist** that directly stimulates dopamine receptors (particularly D2 receptors) and has a longer half-life than levodopa, providing more continuous dopaminergic stimulation [1]. - While dopamine agonists are also effective for motor fluctuations, **Selegiline** is often preferred as an initial adjunct due to its better tolerability profile and lower risk of inducing dyskinesias. - Bromocriptine can cause more side effects including **dyskinesias**, **hallucinations**, and **nausea**, particularly in elderly patients [1]. *Amantadine* - **Amantadine** is an **NMDA receptor antagonist** primarily used to treat **levodopa-induced dyskinesia** rather than motor fluctuations. - While it has mild antiparkinsonian effects, it is not the preferred agent for managing "on-off" phenomena specifically. - Its mechanism does not directly prolong levodopa's effect or prevent dopamine breakdown. *Rimonabant* - **Rimonabant** is a **cannabinoid receptor 1 (CB1) antagonist** that was previously marketed for obesity and smoking cessation but was **withdrawn from the market** due to serious psychiatric adverse effects including depression and suicidality. - It has **no role** in the management of **Parkinson's disease** or its motor complications.

Q: Which drug is contraindicated in the treatment of absence seizures?

Tiagabine. ***Tiagabine*** - **Tiagabine** is an antiepileptic drug that selectively inhibits the reuptake of **GABA** (gamma-aminobutyric acid) in the brain, thereby increasing GABAergic transmission [1, 2, 3]. This mechanism is primarily effective in **focal seizures** and sometimes in **generalized tonic-clonic seizures** [2, 3]. - While tiagabine is used for other seizure types, it is known to **exacerbate absence seizures**, making it contraindicated in their treatment [1]. This paradoxical effect is thought to be due to its complex influence on thalamocortical networks involved in absence seizure generation [1, 2].*Ethosuximide* - **Ethosuximide** is a first-line agent specifically for **absence seizures**. It acts by blocking **T-type calcium channels** in the thalamic neurons, which are crucial for the generation of the characteristic 3-Hz spike-and-wave discharges of absence seizures. - It is highly effective in reducing or eliminating absence seizures with a favorable side effect profile, making it a preferred choice for this specific seizure type.*Clonazepam* - **Clonazepam** is a **benzodiazepine** that enhances the effect of GABA at GABA-A receptors, leading to increased neuronal inhibition. It is effective in various seizure types, including **absence seizures** and **myoclonic seizures**. - While not a first-line treatment due to its sedative side effects and potential for tolerance, it can be used as an adjunct or alternative when other medications are ineffective or not tolerated.*Valproate* - **Valproate** (valproic acid) is a broad-spectrum antiepileptic drug effective against a wide range of seizure types, including **absence seizures**, myoclonic seizures, and **generalized tonic-clonic seizures**. - Its mechanism of action is multifaceted, involving increased GABA synthesis and decreased degradation, voltage-gated sodium channel blockade, and modulation of T-type calcium channels, making it a highly versatile agent.

Q: Modafinil is a drug used in which of the following conditions?

Shift work disorder. ***Shift work disorder*** - **Modafinil** is a **wake-promoting agent** approved by the FDA for improving wakefulness in patients with excessive sleepiness associated with **shift work sleep disorder**. - It helps individuals maintain alertness during atypical work hours, overcoming disruption to their natural circadian rhythm. - **Note:** Modafinil's **primary indication is narcolepsy**, but among the given options, shift work disorder is the correct answer. *Chronic fatigue syndrome* - While fatigue is a primary symptom of **chronic fatigue syndrome**, modafinil is generally **not recommended** as a standard treatment. - Its efficacy in this condition is limited and inconsistent, and management focuses on symptom control and lifestyle adjustments. *Chronic pain syndrome* - **Modafinil has no direct analgesic properties** and is not indicated for **chronic pain syndrome**. - Treatment for chronic pain involves addressing underlying causes with appropriate analgesics or interventional therapies. *Insomnia* - **Modafinil is a wakefulness-promoting agent** and would be **contraindicated in insomnia**, as it would worsen the inability to sleep. - Insomnia is treated with sleep hygiene, cognitive behavioral therapy, or sedative-hypnotics.

Q: All of the following are CNS stimulants except?

Benzodiazepines. ***Correct Answer: Benzodiazepines*** - **Benzodiazepines** are the correct answer because they are central nervous system (CNS) **depressants**, NOT stimulants. - They enhance the effect of the neurotransmitter **GABA** at the GABA-A receptor, leading to decreased neuronal excitability. - They cause sedation, anxiolysis, muscle relaxation, and anticonvulsant effects. *Incorrect: Amphetamines* - **Amphetamines** are potent CNS **stimulants** that increase the release of dopamine and norepinephrine, leading to increased alertness, energy, and focus. - They are commonly prescribed for conditions like attention-deficit/hyperactivity disorder (ADHD) and narcolepsy, but also have high potential for abuse. *Incorrect: Cocaine* - **Cocaine** is a powerful CNS **stimulant** that blocks the reuptake of dopamine, norepinephrine, and serotonin in the brain, resulting in a rapid onset of euphoria, increased energy, and heightened sensory perception. - Its effects are short-lived, leading to a strong craving for more, and it has significant cardiovascular and neurological risks. *Incorrect: Methylphenidate* - **Methylphenidate** is a CNS **stimulant** structurally similar to amphetamines, primarily used in the treatment of ADHD and narcolepsy. - It works by blocking the reuptake of dopamine and norepinephrine, increasing the concentration of these neurotransmitters in the synaptic cleft, and improving attention and focus.

Q: What is the drug of choice for aborting the acute attack of migraine?

Triptans such as sumatriptan. ***Triptans such as sumatriptan*** - **Triptans** are **serotonin 5-HT1B/1D receptor agonists** that cause **vasoconstriction** of intracranial blood vessels and inhibit pronociceptive neuropeptide release, making them highly effective for acute migraine attacks. - They are considered the **first-line specific treatment** for moderate to severe migraine pain or when NSAIDs are ineffective. *NSAIDs such as indomethacin* - **NSAIDs** are effective for mild to moderate migraine attacks but are generally **less effective** than triptans for severe attacks. - While they can reduce inflammation and pain, their mechanism of action is **non-specific** compared to triptans in targeting migraine pathology. *Opioids such as morphine* - **Opioids** are generally **not recommended** for acute migraine treatment due to their potential for **abuse, dependence**, and lack of specific anti-migraine effects. - They can also worsen migraine outcomes over time and contribute to **medication overuse headache**. *Glucocorticoids* - **Glucocorticoids** like dexamethasone may be used as **adjunctive therapy** to prevent migraine recurrence, particularly in status migrainosus. - However, they are **not the primary drug of choice** for aborting an acute attack due to their slower onset of action and broad side effect profile.

Q: Which of the following drug pairs is correctly matched?

Peripheral decarboxylase inhibitor - Benserazide. ***Peripheral decarboxylase inhibitor - Benserazide*** - **Benserazide** is a **peripheral decarboxylase inhibitor** that is commonly co-administered with **levodopa** to prevent its metabolism in the periphery. - By inhibiting the breakdown of levodopa outside the brain, **more levodopa can cross the blood-brain barrier**, where it is then converted to dopamine. *MAO-A inhibitor - Selegiline* - **Selegiline** is an **MAO-B inhibitor**, not an MAO-A inhibitor. It selectively inhibits the enzyme **monoamine oxidase B**, which is responsible for dopamine breakdown in the brain. - **MAO-A inhibitors** (like moclobemide) are primarily used as antidepressants, as they inhibit the breakdown of serotonin and norepinephrine. *COMT inhibitor - Rasagiline* - **Rasagiline** is an **MAO-B inhibitor**, similar to selegiline, used in the treatment of **Parkinson's disease** to reduce the breakdown of dopamine. - **COMT inhibitors** (like entacapone and tolcapone) block the enzyme **catechol-O-methyltransferase**, another enzyme involved in the peripheral and central metabolism of levodopa and dopamine. *Dopamine agonist - Amantadine* - **Amantadine** is an **antiviral drug** that also has **anti-Parkinsonian effects**, primarily through its influence on dopamine release and reuptake, as well as NMDA receptor antagonism. - While it modulates dopamine, it is not classified as a direct **dopamine agonist**; true dopamine agonists (like pramipexole and ropinirole) directly stimulate dopamine receptors.

Question 1

Which drug is given in the pain due to diabetic neuropathy?

Accepted Answer

Gabapentin

Answer

Lamotrigine

Answer

Na valproate

Answer

Morphine

Question 2

Which of the following is not true about benzodiazepines?

Accepted Answer

REM, and Stage 3 and 4 sleep is increased

Answer

Can produce ataxia

Answer

Has GABA facilitatory but no GABA mimetic action

Answer

Produces muscle relaxation by action on spinal cord

Question 3

Which of the following is true about barbiturates?

Accepted Answer

Shows GABA facilitatory action

Answer

Limbic system is most sensitive to the depressive action of barbiturates to CNS

Answer

Enhances GABAergic activity by mimicking GABA's effects

Answer

Primarily acts by blocking voltage gated Na+ and K+ channels

Question 4

Which of the following is used for the patient on antiparkinsonian medication levodopa + carbidopa, but patient showing marked on-off effect?

Accepted Answer

Selegiline

Answer

Bromocriptine

Answer

Amantadine

Answer

Rimonabant

Question 5

Which drug is contraindicated in the treatment of absence seizures?

Accepted Answer

Tiagabine

Answer

Clonazepam

Answer

Ethosuximide

Answer

Valproate

Question 6

Modafinil is a drug used in which of the following conditions?

Accepted Answer

Shift work disorder

Answer

Chronic fatigue syndrome

Answer

Chronic pain syndrome

Answer

Insomnia

Question 7

All of the following are CNS stimulants except?

Accepted Answer

Benzodiazepines

Answer

Cocaine

Answer

Methylphenidate

Answer

Amphetamines

Question 8

Which of the following statements about the anti-Parkinson drug levodopa is true?

Accepted Answer

Only a small percentage of administered levodopa crosses the blood-brain barrier (approximately 2%).

Answer

Levodopa is an active metabolite of dopamine.

Answer

About 50% of administered levodopa is peripherally converted to dopamine.

Answer

Levodopa is not used in the management of hepatic coma.

Question 9

What is the drug of choice for aborting the acute attack of migraine?

Accepted Answer

Triptans such as sumatriptan

Answer

NSAIDs such as indomethacin

Answer

Opioids such as morphine

Answer

Glucocorticoids

Question 10

Which of the following drug pairs is correctly matched?

Accepted Answer

Peripheral decarboxylase inhibitor - Benserazide

Answer

Dopamine agonist - Amantadine

Answer

COMT inhibitor - Rasagiline

Answer

MAO-A inhibitor - Selegiline

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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