Central Nervous System Pharmacology Practice Questions

Q: Which of the following statements about oxcarbazepine is incorrect?

Less chances of hyponatremia than carbamazepine. ***Correct Answer: Less chances of hyponatremia than carbamazepine*** - This statement is **incorrect** because oxcarbazepine has a **higher incidence of hyponatremia** (up to 25% of patients) compared to carbamazepine (5-10%). - Hyponatremia is a well-known and dose-related adverse effect of oxcarbazepine, often requiring monitoring of serum sodium levels. - This is the most definitively incorrect statement among the options. *Incorrect: Metabolises itself* - While this statement is somewhat ambiguous, it likely refers to **autoinduction of metabolism**, which is a characteristic of **carbamazepine** [1]. - **Oxcarbazepine** is a prodrug that is rapidly converted to its active metabolite monohydroxy derivative (MHD), but it **does not autoinduce its own metabolism** to a significant extent like carbamazepine does [1]. - However, if interpreted literally, oxcarbazepine does undergo metabolism, making this statement potentially confusing. *Incorrect: Less chances of hepatotoxicity than carbamazepine* - This statement is **correct** about oxcarbazepine. It is generally associated with a **lower risk of severe hepatotoxicity** [1] compared to carbamazepine. - While liver enzyme elevations can occur, serious liver damage is much less common with oxcarbazepine. *Incorrect: It is less enzyme inducer than carbamazepine* - This statement is **correct** about oxcarbazepine. Its active metabolite MHD is a **weaker inducer of cytochrome P450 enzymes** (especially CYP3A4) than carbamazepine. - This translates to fewer and less significant drug-drug interactions with oxcarbazepine.

Q: What is the classification of Rotigotine?

Dopamine agonist. ***Dopamine agonist*** - Rotigotine is classified as a **non-ergoline dopamine agonist**, meaning it directly stimulates dopamine receptors in the brain. - It is used in the treatment of **Parkinson's disease** and **restless legs syndrome** by mimicking the effects of dopamine. *Dopamine antagonist* - **Dopamine antagonists** block dopamine receptors and are typically used as antipsychotics or antiemetics. - This classification would have opposite pharmacological effects to what is seen with rotigotine. *GABA agonist* - **GABA agonists** enhance the effects of the inhibitory neurotransmitter GABA, leading to sedation or seizure control. - This mechanism of action is unrelated to rotigotine's primary effects on dopamine pathways. *GABA antagonist* - **GABA antagonists** block GABA receptors, which can lead to increased neuronal excitability and seizures. - This is not the mechanism of action for rotigotine, which targets the dopaminergic system.

Q: Patient on treatment with carbidopa + levodopa for 10 years now has wearing-off effect. What should be added to restore action?

Tolcapone. ***Tolcapone*** - **Tolcapone** is a **catechol-O-methyltransferase (COMT) inhibitor** that prevents the peripheral breakdown of levodopa, increasing its availability to the brain. - Adding a COMT inhibitor is the **primary strategy** to mitigate the **wearing-off effect** in patients receiving chronic levodopa therapy by prolonging levodopa's half-life and duration of action. - COMT inhibitors directly extend the duration of each levodopa dose, making them first-line adjuncts for wearing-off phenomenon. *Rasagiline* - **Rasagiline** is a **monoamine oxidase-B (MAO-B) inhibitor** used in Parkinson's disease to reduce the breakdown of dopamine in the brain. - It is also effective as an adjunct in treating **wearing-off** and can reduce daily off-time, though COMT inhibitors are typically preferred as first-line agents for this specific indication. - MAO-B inhibitors work by increasing central dopamine levels rather than directly extending levodopa's duration. *Benzhexol* - **Benzhexol** (also known as trihexyphenidyl) is an **anticholinergic agent** primarily used to treat tremor and dystonia in Parkinson's disease, especially in younger patients. - It does not address the aetiology of the **wearing-off phenomenon**, which is due to fluctuating levodopa levels and dopamine deficiency. *Amantadine* - **Amantadine** is an **NMDA receptor antagonist** used primarily to reduce **dyskinesias** associated with long-term levodopa therapy in Parkinson's disease. - While it has some efficacy in early Parkinson's and improving motor fluctuations, it is not the primary intervention for the **wearing-off effect** where reduced duration of benefit from levodopa is the main issue.

Q: Which of the following drugs does not potentiate the effect of NMDA at NMDA receptors?

Ketamine. ***Ketamine*** - **Ketamine** is an **NMDA receptor antagonist**, meaning it blocks the activity of NMDA receptors rather than potentiating it. - It binds to a site within the **NMDA receptor channel**, preventing ion flow and neuronal excitation. - Used clinically as a dissociative anesthetic and for treatment-resistant depression. *Aspartic acid* - **Aspartic acid** functions as an **excitatory neurotransmitter** and is an **agonist** at NMDA receptors. - It readily activates these receptors by binding to the glutamate-binding site, thereby potentiating their effects. *D-serine* - **D-serine** acts as an **endogenous co-agonist** at the NMDA receptor by binding to the **glycine regulatory site** (also called the glycine-B site). - Its binding is essential for the full activation and potentiation of NMDA receptor activity. - Along with glycine, it is one of the primary physiological co-agonists required for NMDA receptor function. *Homocysteic acid* - **Homocysteic acid** is an **endogenous excitatory amino acid** that acts as an **agonist** at NMDA receptors. - It directly binds to and activates NMDA receptors at the glutamate-binding site, thus potentiating their effects.

Q: Which drug is used in amytrophic lateral sclerosis?

Riluzole. ***Riluzole*** - **Riluzole** is an **NMDA receptor antagonist** that is approved for the treatment of **amyotrophic lateral sclerosis (ALS)**. - It works by reducing **glutamate-mediated excitotoxicity**, which is thought to contribute to neuronal damage in ALS, thereby extending survival time and delaying the need for tracheostomy. *Glatiramer acetate* - **Glatiramer acetate** is an immunomodulating drug used in the treatment of **multiple sclerosis (MS)**. - It is believed to work by inducing and activating **T-suppressor cells** specific for myelin basic protein, thus reducing the frequency of relapses in MS. *Tacrine* - **Tacrine** is an **acetylcholinesterase inhibitor** that was previously used for the treatment of **mild to moderate Alzheimer's disease**. - Its use has largely been replaced by newer, better-tolerated drugs due to its significant **hepatotoxicity** and frequent dosing schedule. *Olanzapine* - **Olanzapine** is an **atypical antipsychotic** medication used to treat conditions such as **schizophrenia** and **bipolar disorder**. - It primarily exerts its effects by blocking **dopamine D2** and **serotonin 5-HT2A** receptors.

Q: What is the drug of choice for treating restless leg syndrome in a woman who developed pain and crawling sensation on her legs at night?

Pramipexole. ***Pramipexole*** - **Pramipexole** is a **dopamine agonist** (D2/D3 receptor agonist) that is highly effective in treating **restless leg syndrome (RLS)** and is FDA-approved for moderate-to-severe RLS. - It helps alleviate the characteristic **pain, crawling sensations (paresthesias)**, and the urge to move the legs, especially at night. - **First-line treatment** along with other dopamine agonists like ropinirole and rotigotine. - **Preferred in many guidelines** as a primary pharmacological option for RLS. *Gabapentin* - **Gabapentin** (and gabapentin enacarbil) is an **alpha-2-delta ligand** that is also considered a **first-line treatment option** for RLS per recent guidelines. - Particularly useful in patients with **comorbid insomnia, neuropathic pain**, or when there is concern about **augmentation** (worsening of symptoms with long-term dopamine agonist use). - While equally effective, **dopamine agonists like pramipexole** are more traditionally recognized as the primary choice in conventional teaching and previous exam questions. *Vitamin B12* - **Vitamin B12 deficiency** can cause **neurological symptoms** like numbness or tingling, but supplementation is **not a direct treatment for primary RLS** unless a specific deficiency is identified and contributing to symptoms. - No direct evidence supporting **Vitamin B12 supplementation** as a primary treatment for RLS itself. *Iron tablets* - **Iron deficiency** (ferritin <75 μg/L) is a common and important cause of **secondary RLS**, and **iron supplementation** should be considered when low iron stores are identified. - However, for primary RLS or without confirmed iron deficiency, iron tablets are **not the primary pharmacological treatment**, and dopamine agonists like pramipexole remain the preferred initial option.

Q: Modafinil is primarily used for the treatment of which of the following conditions?

Narcolepsy. ***Narcolepsy*** - **Modafinil** is a **eugeroic** (wakefulness-promoting agent) specifically approved and widely used for the treatment of excessive daytime sleepiness associated with **narcolepsy**. - Its mechanism involves increasing **dopamine** and **norepinephrine** levels, and modulating **orexin** pathways, promoting alertness without significant psychomotor stimulation. *Sexual dysfunction* - While sometimes explored off-label for certain types of sexual dysfunction, **modafinil** is not a primary or approved treatment for this condition. - Primary treatments for sexual dysfunction often involve specific medications like **PDE5 inhibitors** or hormone therapy, depending on the cause. *Depression* - **Modafinil** is not a primary antidepressant, although it can be used as an **adjunctive therapy** in some cases to combat residual fatigue or hypersomnia associated with depression. - Standard treatment for depression involves **selective serotonin reuptake inhibitors (SSRIs)**, **serotonin-norepinephrine reuptake inhibitors (SNRIs)**, or other classes of antidepressants. *Anxiety* - **Modafinil** is a stimulant-like drug and can sometimes **exacerbate anxiety** in susceptible individuals due to its catecholaminergic effects. - Primary treatments for anxiety disorders include **selective serotonin reuptake inhibitors (SSRIs)**, **benzodiazepines** (for acute relief), and psychotherapy.

Q: What is the drug of choice (DOC) for smoking cessation?

Varenicline. ***Varenicline*** - **Varenicline** is a **partial nicotinic receptor agonist** that reduces both the cravings for nicotine and the pleasurable effects of smoking. - It is considered a **first-line agent** for smoking cessation due to its effectiveness in increasing abstinence rates. *Acamprosate* - **Acamprosate** is a medication used to maintain abstinence from **alcohol dependence** by modulating GABA and glutamate neurotransmission. - It is **not indicated** for smoking cessation and has no direct mechanism of action related to nicotine addiction. *Thalidomide* - **Thalidomide** is an **immunomodulatory drug** with anti-angiogenic and anti-inflammatory properties, primarily used in conditions like **multiple myeloma** and **leprosy**. - It has **severe teratogenic effects** and is not used for smoking cessation due to its complex mechanism and significant side effect profile. *Tryptophan* - **Tryptophan** is an **essential amino acid** that serves as a precursor to **serotonin**, a neurotransmitter involved in mood regulation and sleep. - While it can impact mood, it is **not an approved or effective treatment** for directly addressing nicotine dependence or cravings.

Q: Which dopamine receptor blocker is commonly used for intractable Sydenham chorea?

Haloperidol. ***Haloperidol*** - Haloperidol is a **typical antipsychotic** and **dopamine D2 receptor blocker** commonly used for severe or intractable Sydenham chorea due to its efficacy in controlling **hyperkinetic movements**. - Its mechanism of action involves reducing dopaminergic overactivity in the **basal ganglia**, which is implicated in the pathogenesis of chorea. - While effective, it carries a risk of **extrapyramidal side effects** and requires monitoring. *Valproate* - Valproate is an **anticonvulsant** and **mood stabilizer** that IS actually used as a **first-line treatment** for Sydenham chorea, often preferred due to better tolerability compared to typical antipsychotics. - However, valproate is **not a dopamine receptor blocker** - it works through GABAergic mechanisms and sodium channel blockade. - The question specifically asks for a dopamine receptor blocker, making haloperidol the correct answer. *Warfarin* - Warfarin is an **anticoagulant** prescribed to prevent **thromboembolic events**, and has no role in the treatment of Sydenham chorea. - Its mechanism involves inhibiting **vitamin K-dependent clotting factors**, which is unrelated to neurological movement disorders. *Risperidone* - Risperidone is an **atypical antipsychotic** that blocks both **dopamine D2** and **serotonin 5-HT2A receptors**. While it can be effective for chorea, it is generally considered a **second-line agent**. - It may be used when typical antipsychotics are poorly tolerated, offering potentially lower risk of **extrapyramidal side effects** compared to haloperidol, though it still carries risks.

Q: What is the primary component extracted from the Cannabis Indica plant used in traditional medicine?

Flowers of Cannabis Indica. ***Flowers of Cannabis Indica*** - The **flowers** (also called buds or flowering tops) are the primary component extracted from *Cannabis Indica* for traditional and modern medicinal use. - The female flowers contain the highest concentration of **trichomes**, which produce cannabinoids such as **THC** and **CBD**. - In traditional medicine systems including Ayurveda, the **flowering tops** were the principal medicinal part used. - The flowers are the **primary botanical source** from which all cannabis-based medicines are derived. *Resin of Cannabis Indica* - Resin refers to concentrated **secondary extracts** like hashish or cannabis oil, which are processed products derived from the flowers. - While resin has high cannabinoid content, it is not the primary plant component but rather a concentrated derivative. - Resin is obtained by processing the trichomes from the flowers, making it a downstream product. *Leaves of Cannabis Indica* - While leaves contain some cannabinoids, their concentration is generally much **lower** compared to the flowers. - Leaves are less commonly used as the primary medicinal component due to their significantly lower potency. - They may be used in some traditional preparations but are not the primary component. *Stem of Cannabis Indica* - The stem primarily consists of **fibrous material** and has minimal cannabinoid concentration. - It is not traditionally used as a medicinal component due to its lack of significant active ingredients. - Stems are primarily used for fiber (hemp) rather than medicinal applications.

Question 1

Which of the following statements about oxcarbazepine is incorrect?

Accepted Answer

Less chances of hyponatremia than carbamazepine

Answer

Metabolises itself

Answer

Less chances of hepatotoxicity than carbamazepine

Answer

It is less enzyme inducer than carbamazepine

Question 2

What is the classification of Rotigotine?

Accepted Answer

Dopamine agonist

Answer

Dopamine antagonist

Answer

GABA agonist

Answer

GABA antagonist

Question 3

Patient on treatment with carbidopa + levodopa for 10 years now has wearing-off effect. What should be added to restore action?

Accepted Answer

Tolcapone

Answer

Benzhexol

Answer

Rasagiline

Answer

Amantadine

Question 4

Which of the following drugs does not potentiate the effect of NMDA at NMDA receptors?

Accepted Answer

Ketamine

Answer

Aspartic acid

Answer

D-serine

Answer

Homocysteic acid

Question 5

Which drug is used in amytrophic lateral sclerosis?

Accepted Answer

Riluzole

Answer

Tacrine

Answer

Olanzapine

Answer

Glatiramer acetate

Question 6

What is the drug of choice for treating restless leg syndrome in a woman who developed pain and crawling sensation on her legs at night?

Accepted Answer

Pramipexole

Answer

Gabapentin

Answer

Vitamin B12

Answer

Iron tablets

Question 7

Modafinil is primarily used for the treatment of which of the following conditions?

Accepted Answer

Narcolepsy

Answer

Sexual dysfunction

Answer

Depression

Answer

Anxiety

Question 8

What is the drug of choice (DOC) for smoking cessation?

Accepted Answer

Varenicline

Answer

Acamprosate

Answer

Thalidomide

Answer

Tryptophan

Question 9

Which dopamine receptor blocker is commonly used for intractable Sydenham chorea?

Accepted Answer

Haloperidol

Answer

Warfarin

Answer

Risperidone

Answer

Valproate

Question 10

What is the primary component extracted from the Cannabis Indica plant used in traditional medicine?

Accepted Answer

Flowers of Cannabis Indica

Answer

Leaves of Cannabis Indica

Answer

Resin of Cannabis Indica

Answer

Stem of Cannabis Indica

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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