Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology Indian Medical PG Practice Questions and MCQs

Question 211: All of the following drugs are atypical antipsychotics EXCEPT?

A. Olanzapine
B. Clozapine
C. Risperidone
D. Thioridazine (Correct Answer)

Explanation: **Explanation:** Antipsychotics are broadly classified into two categories: **Typical (First Generation)** and **Atypical (Second Generation)**. **Why Thioridazine is the correct answer:** **Thioridazine** is a **Typical Antipsychotic** belonging to the Phenothiazine class (specifically the piperidine subgroup). Its primary mechanism of action is the potent blockade of **D2 receptors** in the mesolimbic pathway. Unlike atypical agents, it has a higher propensity for causing extrapyramidal side effects (EPS), though less than Haloperidol due to its inherent anticholinergic activity. **Why the other options are incorrect:** * **Clozapine:** The prototype **Atypical Antipsychotic**. It has a higher affinity for **5-HT2A receptors** than D2 receptors. It is the gold standard for treatment-resistant schizophrenia. * **Olanzapine:** An atypical agent closely related to clozapine but without the risk of agranulocytosis. It is notorious for causing significant weight gain and metabolic syndrome. * **Risperidone:** A potent atypical antipsychotic that blocks both D2 and 5-HT2A receptors. At higher doses, it behaves more like a typical antipsychotic and can significantly elevate prolactin levels. **High-Yield Clinical Pearls for NEET-PG:** * **Thioridazine Warning:** It is uniquely associated with **Mellaril-induced Retinitis Pigmentosa** (at doses >800mg/day) and significant **QT interval prolongation**, which can lead to Torsades de Pointes. * **Atypical Advantage:** They treat both positive and negative symptoms of schizophrenia and have a lower risk of Extrapyramidal Symptoms (EPS). * **Clozapine Monitoring:** Requires mandatory WBC monitoring due to the risk of **Agranulocytosis**. It is also the only antipsychotic proven to reduce suicide risk in schizophrenia.

Question 212: Which of the following anti-Parkinson drugs has the potential to cause retroperitoneal fibrosis?

A. Pramipexole
B. Entacapone
C. Bromocriptine (Correct Answer)
D. Ropinirole

Explanation: **Explanation:** **Bromocriptine** is the correct answer because it belongs to the **Ergot-derivative** class of dopamine agonists. Ergot derivatives (which also include Pergolide and Cabergoline) are known to cause **fibrotic complications** such as retroperitoneal, pleuropulmonary, and cardiac valvular fibrosis. This is thought to be mediated by the activation of **5-HT2B receptors**, which stimulates fibroblast proliferation. Due to these serious side effects, the use of ergot-derived agonists has largely been superseded by non-ergot compounds. **Analysis of Incorrect Options:** * **Pramipexole (A) and Ropinirole (D):** These are **Non-ergot** dopamine agonists. They are preferred in clinical practice because they do not cause fibrotic complications. Their side effect profile typically includes impulse control disorders (pathological gambling), sleep attacks, and nausea. * **Entacapone (B):** This is a peripheral **COMT inhibitor** used as an adjunct to Levodopa to prevent its peripheral metabolism. Its characteristic side effect is orange discoloration of urine, not fibrosis. **NEET-PG High-Yield Pearls:** * **Fibrosis Rule:** If a dopamine agonist is an "Ergot" derivative, think of "Fibrosis." * **Pramipexole** is specifically noted for its antioxidant properties and is excreted unchanged in the urine (requires dose adjustment in renal failure). * **Apomorphine** is the dopamine agonist used as a "rescue" therapy for "off" episodes in Parkinson’s disease, administered subcutaneously. * **Impulse Control Disorders** (hypersexuality, gambling) are most strongly associated with the non-ergot agonists (Pramipexole, Ropinirole).

Question 213: Which condition has seen cannabinoids approved by the USFDA for a new use in June 2018?

A. Epilepsy (Correct Answer)
B. Urinary Tract Infection
C. Tuberculosis
D. Varicella (Chicken Pox)

Explanation: **Explanation:** The correct answer is **Epilepsy**. In June 2018, the USFDA approved **Epidiolex** (a purified form of **Cannabidiol** or CBD) for the treatment of seizures associated with two rare and severe forms of epilepsy: **Lennox-Gastaut syndrome** and **Dravet syndrome**, in patients two years of age and older. This marked the first FDA-approved drug derived from marijuana. **Why the other options are incorrect:** * **Urinary Tract Infection (B):** UTIs are bacterial infections typically treated with antibiotics (e.g., Nitrofurantoin, Fosfomycin). Cannabinoids have no established antimicrobial role in treating acute infections. * **Tuberculosis (C):** TB is caused by *Mycobacterium tuberculosis* and requires a specific regimen of antitubercular drugs (RIPE: Rifampin, Isoniazid, Pyrazinamide, Ethambutol). * **Varicella (D):** Chickenpox is a viral infection caused by the Varicella-Zoster virus. Management involves supportive care or antivirals like Acyclovir; cannabinoids are not indicated. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Unlike THC, Cannabidiol (CBD) does not produce a "high" (non-psychoactive). Its anticonvulsant effect is thought to involve the modulation of intracellular calcium and adenosine signaling, rather than direct action on CB1/CB2 receptors. * **Other FDA-approved Cannabinoids:** **Dronabinol** and **Nabilone** are synthetic cannabinoids used for chemotherapy-induced nausea and vomiting (CINV) and anorexia associated with weight loss in AIDS patients. * **Side Effects:** Common side effects of Epidiolex include somnolence, decreased appetite, diarrhea, and potential elevation of liver enzymes (transaminases).

Question 214: Alpha 2 agonists cause all of the following except:

A. Analgesia
B. Hyperalgesia (Correct Answer)
C. Sedation
D. Anxiolysis

Explanation: **Explanation:** Alpha-2 ($\alpha_2$) adrenergic agonists (such as **Clonidine** and **Dexmedetomidine**) act primarily by stimulating presynaptic $\alpha_2$ receptors in the Central Nervous System (CNS). This leads to a decrease in the release of norepinephrine, resulting in a sympatholytic effect. **Why Hyperalgesia is the Correct Answer:** Hyperalgesia refers to an increased sensitivity to pain. $\alpha_2$ agonists do the exact opposite; they are potent **analgesics**. They inhibit the firing of nociceptive neurons in the dorsal horn of the spinal cord and modulate pain pathways in the locus coeruleus. Therefore, they cause analgesia, not hyperalgesia. **Analysis of Incorrect Options:** * **Analgesia:** $\alpha_2$ agonists provide significant pain relief by reducing substance P release and interfering with pain transmission in the spinal cord. They are often used as adjuvants in regional anesthesia. * **Sedation:** By acting on the **locus coeruleus** (the primary noradrenergic nucleus in the brainstem), these drugs decrease wakefulness. Dexmedetomidine is unique because it produces "conscious sedation," where the patient remains easily arousable. * **Anxiolysis:** The reduction of central sympathetic outflow effectively lowers anxiety levels, making these drugs useful for preoperative medication. **High-Yield Clinical Pearls for NEET-PG:** * **Dexmedetomidine:** Highly selective $\alpha_2$ agonist; used for ICU sedation as it causes minimal respiratory depression. * **Clonidine:** Used in hypertension, opioid withdrawal, and ADHD. * **Side Effects:** The most common side effects are **hypotension** and **bradycardia** (due to decreased sympathetic tone) and **xerostomia** (dry mouth). * **Mnemonic:** $\alpha_2$ agonists cause the "3 Ss": **S**edation, **S**ympatholysis, and **S**pinal Analgesia.

Question 215: Which of the following drugs is used for the prophylaxis of migraine but not for angina pectoris?

A. Verapamil
B. Diltiazem
C. Flunarizine (Correct Answer)
D. Amlodipine

Explanation: **Explanation:** The correct answer is **Flunarizine**. **1. Why Flunarizine is Correct:** Flunarizine is a **non-selective calcium channel blocker (CCB)** that also possesses H1-antihistaminic, dopamine D2 blocking, and sodium channel blocking properties. Unlike conventional CCBs, it is highly lipophilic and crosses the blood-brain barrier, acting primarily on the CNS. It is specifically indicated for the **prophylaxis of migraine** and vertigo. However, it has **no significant effect on systemic vascular resistance or myocardial oxygen demand**, making it ineffective for the treatment or prophylaxis of angina pectoris. **2. Why the Other Options are Incorrect:** * **Verapamil & Diltiazem (Options A & B):** These are non-dihydropyridine CCBs. They have significant negative inotropic and chronotropic effects on the heart and cause peripheral vasodilation. They are first-line agents for **angina pectoris** [1], [2]. Verapamil is also used off-label for migraine prophylaxis (though less commonly than beta-blockers), but since it is used for both, it does not fit the question's criteria. * **Amlodipine (Option D):** This is a dihydropyridine CCB used extensively for hypertension and **chronic stable/vasospastic angina** [1]. It has no established role in migraine prophylaxis. **3. High-Yield Clinical Pearls for NEET-PG:** * **Side Effects of Flunarizine:** Due to its D2-blocking activity, it can cause **Extrapyramidal Symptoms (EPS)** and **Parkinsonism**, especially in the elderly. It is also known to cause significant weight gain and sedation. * **Drug of Choice (DOC):** While Flunarizine is used, **Propranolol** remains the DOC for migraine prophylaxis [3]. * **Mechanism in Migraine:** Flunarizine prevents intracellular calcium overload during the cortical spreading depression phase of a migraine attack.

Question 216: What is the drug of choice for infantile spasms associated with tuberous sclerosis?

A. Vigabatrin (Correct Answer)
B. Valproate
C. Barbiturate
D. Ethosuximide

Explanation: **Explanation:** **1. Why Vigabatrin is the Correct Answer:** Infantile spasms (West Syndrome) are characterized by a triad of spasms, hypsarrhythmia on EEG, and mental retardation. While **ACTH** is generally considered the first-line treatment for idiopathic cases, **Vigabatrin** is the specific **drug of choice (DOC)** when infantile spasms are associated with **Tuberous Sclerosis**. * **Mechanism:** Vigabatrin acts as an irreversible inhibitor of GABA-transaminase, the enzyme responsible for degrading GABA. This leads to increased levels of GABA (the primary inhibitory neurotransmitter) in the brain, which effectively suppresses the spasms. **2. Why Other Options are Incorrect:** * **Valproate (B):** While Valproate is a broad-spectrum anticonvulsant and can be used as a second-line agent for infantile spasms, it is not the specific DOC for Tuberous Sclerosis-associated cases. * **Barbiturates (C):** Phenobarbital is primarily used for neonatal seizures and focal seizures. It is not effective for the specific pathophysiology of infantile spasms. * **Ethosuximide (D):** This is the drug of choice for **Absence Seizures** (3 Hz spike-and-wave). It works by blocking T-type calcium channels and has no role in treating West Syndrome. **3. High-Yield Clinical Pearls for NEET-PG:** * **Side Effect Alert:** The most characteristic side effect of Vigabatrin is **permanent visual field constriction** (concentric peripheral field loss), requiring regular ophthalmological monitoring. * **Tuberous Sclerosis Triad (Vogt’s Triad):** Adenoma sebaceum, mental retardation, and seizures. * **DOC Summary:** * Infantile Spasms (General): ACTH. * Infantile Spasms (Tuberous Sclerosis): Vigabatrin. * Absence Seizures: Ethosuximide. * Myoclonic Seizures: Sodium Valproate.

Question 217: For which of the following seizures would Carbamazepine be prescribed as the appropriate drug treatment for prevention?

A. Generalized tonic clonic
B. Simple partial
C. Status epilepticus
D. Complex partial (Correct Answer)

Explanation: **Explanation:** **Carbamazepine (CBZ)** is a first-line antiepileptic drug primarily used for the management of focal (partial) seizures. Its mechanism of action involves the **blockade of voltage-gated sodium channels** in their inactivated state, which prevents high-frequency repetitive firing of action potentials. 1. **Why Complex Partial is Correct:** Carbamazepine is considered a drug of choice for both **Simple and Complex Partial seizures**, as well as Generalized Tonic-Clonic Seizures (GTCS). In clinical practice and exam scenarios, it is highly associated with the management of complex partial seizures due to its efficacy and established safety profile for focal epilepsy. 2. **Why other options are incorrect:** * **Generalized Tonic-Clonic (A):** While CBZ is effective for GTCS, it is often secondary to Valproate (which covers a broader spectrum) or Levetiracetam. * **Simple Partial (B):** CBZ is used here, but "Complex Partial" is the more classic association for this specific question type. * **Status Epilepticus (C):** This is a medical emergency requiring rapid-acting intravenous drugs. The drugs of choice are **Lorazepam/Diazepam** (to stop the seizure) followed by **Fosphenytoin/Phenytoin** (for maintenance). CBZ is not used here as it lacks an IV formulation and has a slow onset. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Carbamazepine is the DOC for **Trigeminal Neuralgia**. * **Side Effects:** It is a potent **enzyme inducer** (CYP3A4). Watch for **Diplopia** (earliest sign of toxicity), **SIADH** (hyponatremia), and **Stevens-Johnson Syndrome** (especially in patients with HLA-B*1502 allele). * **Contraindication:** CBZ **exacerbates Absence and Myoclonic seizures**; never use it if these are suspected.

Question 218: All of the following are approved for the treatment of relapsing-remitting multiple sclerosis (RRMS) subtype, except?

A. Interferon beta-1a
B. Interferon beta-1b
C. Glatiramer
D. Mycophenolate (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Mycophenolate**. Multiple Sclerosis (MS) is a chronic autoimmune demyelinating disease of the CNS. Treatment is divided into managing acute relapses (Corticosteroids) and **Disease-Modifying Therapies (DMTs)** to reduce the frequency of relapses in the Relapsing-Remitting (RRMS) subtype. **Why Mycophenolate is the correct answer:** While Mycophenolate mofetil is a potent immunosuppressant used in organ transplantation and certain autoimmune conditions (like Lupus Nephritis), it is **not FDA-approved** for the treatment of RRMS. It is occasionally used "off-label" in refractory cases, but it does not hold a standard indication for MS. **Analysis of Incorrect Options:** * **Interferon beta-1a & 1b:** These were the first first-line DMTs approved for RRMS. They work by modulating the immune response, reducing T-cell proliferation, and decreasing the passage of inflammatory cells across the blood-brain barrier. * **Glatiramer Acetate:** This is a synthetic polypeptide mixture that mimics **Myelin Basic Protein**. It acts as a "decoy," diverting the autoimmune attack away from the patient's myelin. It is a standard first-line injectable therapy for RRMS. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Acute Relapse:** Intravenous Methylprednisolone. * **Oral DMTs for RRMS:** Fingolimod (S1P modulator), Teriflunomide (DHODH inhibitor), and Dimethyl fumarate. * **Monoclonal Antibodies:** Natalizumab (targets α4β1-integrin; risk of PML) and Ocrelizumab (targets CD20; approved for Primary Progressive MS). * **Glatiramer Safety:** It is often considered the safest DMT during pregnancy.

Question 219: Which of the following is a nootropic drug?

A. Rivastigmine
B. Tacrine
C. Amantadine
D. Piracetam (Correct Answer)

Explanation: **Explanation:** **Piracetam** is the correct answer as it is the prototype of the **nootropic** class of drugs (also known as "smart drugs" or cognitive enhancers). Nootropics are substances that aim to improve memory, concentration, and cognitive function without causing significant sedation or stimulation. Piracetam is a cyclic derivative of GABA, though it does not act on GABA receptors. Its mechanism involves improving neuroplasticity, enhancing cerebral microcirculation, and modulating ion channels (AMPAR/NMDAR) to increase ATP production in the brain. **Analysis of Incorrect Options:** * **Rivastigmine & Tacrine (Options A & B):** These are **Centrally acting Cholinesterase Inhibitors**. While they are used to treat cognitive decline in Alzheimer’s disease by increasing acetylcholine levels in the synaptic cleft, they are classified specifically as anti-dementia drugs rather than general nootropics. Tacrine is now rarely used due to hepatotoxicity. * **Amantadine (Option C):** This is an **NMDA receptor antagonist** and dopaminergic agent primarily used in the management of Parkinson’s disease and as an antiviral for Influenza A. **High-Yield Clinical Pearls for NEET-PG:** * **Other Nootropics:** Pyritinol, Citicoline, and Ginkgo biloba. * **Piracetam Clinical Uses:** Apart from cognitive enhancement, it is specifically used in the treatment of **cortical myoclonus** (often in combination with valproate). * **Donepezil:** Currently the first-line drug for symptomatic treatment of Alzheimer’s disease due to its long half-life and better tolerability compared to Tacrine.

Question 220: Naloxone is contraindicated in neonatal resuscitation if the mother is on which of the following substances?

A. Cocaine
B. Amphetamine
C. Methadone (Correct Answer)
D. Heroin

Explanation: The correct answer is **Methadone**. **Mechanism and Rationale:** Naloxone is a competitive opioid antagonist used to reverse respiratory depression. However, it is strictly contraindicated in neonates born to mothers with **chronic opioid dependence** (e.g., Methadone or Heroin maintenance). In these infants, the drug crosses the placenta, leading to physical dependence in utero [1]. Administering Naloxone triggers **acute, severe withdrawal syndrome**, which can manifest as intractable seizures, cardiovascular collapse, and extreme irritability [2]. In neonatal resuscitation, the preferred management for opioid-induced respiratory depression is **positive pressure ventilation (PPV)** rather than pharmacological reversal. **Analysis of Options:** * **Methadone (Correct):** As a long-acting opioid used in maintenance therapy, it causes significant fetal physical dependence. Naloxone administration precipitates immediate withdrawal [1]. * **Heroin:** While also an opioid, Methadone is the more "classic" board exam answer associated with chronic maternal addiction programs. However, Naloxone is contraindicated for *any* chronic opioid exposure (including Heroin) [1]. * **Cocaine & Amphetamine:** These are CNS stimulants, not opioids. Naloxone has no pharmacological effect on stimulant-induced toxicity or withdrawal; therefore, it is neither indicated nor specifically contraindicated in the context of neonatal withdrawal for these substances. **NEET-PG High-Yield Pearls:** * **Drug of Choice for Opioid Overdose:** Naloxone (IV/Intranasal). * **Duration of Action:** Naloxone has a short half-life (30–90 mins); patients must be monitored for "re-narcotization" as the opioid may outlast the antagonist. * **Naltrexone vs. Naloxone:** Naltrexone is orally active with a long half-life, used for alcohol and opioid de-addiction, not acute reversal. * **Neonatal Resuscitation Protocol:** Always prioritize airway and ventilation over Naloxone.

Practice by Chapter

General Anesthetics

Practice Questions

Local Anesthetics

Practice Questions

Sedative-Hypnotics

Practice Questions

Antiepileptic Drugs

Practice Questions

Antiparkinsonian Drugs

Practice Questions

Opioid Analgesics

Practice Questions

Drugs of Abuse and Addiction

Practice Questions

Psychostimulants

Practice Questions

Hallucinogens

Practice Questions

CNS Stimulants and Cognitive Enhancers

Practice Questions

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