Central Nervous System Pharmacology Practice Questions

Q: Valproic acid is used in which of the following disorders?

Sydenham's chorea, Migraine, and Mania only. **Explanation:** Valproic acid (Sodium Valproate) is a broad-spectrum anticonvulsant with a versatile clinical profile. Its mechanism involves increasing GABA levels, inhibiting T-type calcium channels, and blocking voltage-gated sodium channels. **Why Option C is correct:** 1. **Mania:** Valproate is a first-line mood stabilizer used for the treatment of acute manic episodes in Bipolar Disorder and for maintenance therapy. 2. **Migraine:** It is FDA-approved for the **prophylaxis** of migraine (though not for acute attacks). 3. **Sydenham’s Chorea:** Valproate is considered an effective second-line treatment (after diazepam or haloperidol) to control the involuntary movements associated with this condition, especially in refractory cases. **Why other options are incorrect:** * **Obsessive-Compulsive Disorder (OCD):** The primary treatment for OCD involves SSRIs (e.g., Fluoxetine, Fluvoxamine) and Clomipramine (TCA). Valproate is not a standard treatment for OCD and is only rarely used as an off-label augmentation strategy in treatment-resistant cases, making options B and D incorrect. * **Option A** is incomplete as it misses Migraine, a major clinical indication. **High-Yield Clinical Pearls for NEET-PG:** * **Teratogenicity:** Valproate is highly teratogenic, causing **Neural Tube Defects** (specifically Spina Bifida). It should be avoided in pregnancy. * **Side Effects:** Remember the mnemonic **VALPROATE**: **V**omiting, **A**lopecia (curly hair), **L**iver toxicity (Hepatotoxicity), **P**ancreatitis, **R**etention of weight (Obesity), **O**edema, **A**norexia, **T**remors/Thrombocytopenia, and **E**ncephalopathy (due to hyperammonemia). * **Drug of Choice:** It is the drug of choice for **Myoclonic seizures** and generalized tonic-clonic seizures.

Q: What is the drug of choice for relapsing-remitting multiple sclerosis?

Beta interferon. **Relapsing-Remitting Multiple Sclerosis (RRMS)** is the most common form of MS, characterized by episodes of new or worsening neurological symptoms followed by periods of partial or complete recovery [1]. **Why Beta Interferon is the Correct Answer:** **Interferon-beta (IFN-β)**, specifically types 1a and 1b, is considered a first-line disease-modifying therapy (DMT) for RRMS. It works by modulating the immune response: it reduces the movement of inflammatory T-cells across the blood-brain barrier and increases the production of anti-inflammatory cytokines. This leads to a decreased frequency of clinical relapses and a reduction in the formation of new brain lesions on MRI [1], [2]. **Analysis of Incorrect Options:** * **Alpha Interferon (IFN-α):** Primarily used in the treatment of viral infections (Hepatitis B and C) and certain malignancies (Hairy cell leukemia, Kaposi sarcoma). It is not indicated for MS [2]. * **Gamma Interferon (IFN-γ):** This is a pro-inflammatory cytokine. Administering IFN-γ actually **exacerbates** MS symptoms and increases relapse rates; it is used clinically for Chronic Granulomatous Disease (CGD) [2]. * **Natalizumab:** While highly effective for RRMS, it is generally reserved as a second-line agent or for rapidly progressing disease due to the risk of **Progressive Multifocal Leukoencephalopathy (PML)** caused by JC virus reactivation. **High-Yield Clinical Pearls for NEET-PG:** * **Glatiramer acetate** is another first-line alternative for RRMS, especially in patients who cannot tolerate interferons [1]. * **Drug of Choice for Acute Attack:** Intravenous Methylprednisolone (High-dose steroids). * **Oral Drugs for MS:** Fingolimod (S1P modulator), Teriflunomide, and Dimethyl fumarate. * **Side Effects of IFN-β:** Flu-like symptoms (most common) and injection site reactions [2]. Pre-medication with NSAIDs is often recommended.

Q: "Shivering" is observed in the early postoperative period due to:

Halothane. **Explanation:** **Halothane** is the correct answer because it is classically associated with **postoperative shivering** (also known as "halothane shakes"). This phenomenon occurs during the recovery phase of anesthesia. **Mechanism:** Halothane causes significant peripheral vasodilation and depresses the hypothalamic thermoregulatory center. This leads to a drop in core body temperature (hypothermia). As the anesthetic wears off, the body’s thermoregulatory mechanisms regain function and attempt to restore normal temperature through vigorous shivering. While other volatile anesthetics can cause this, it is most characteristic of Halothane in classical pharmacology. **Analysis of Incorrect Options:** * **A. Chloroform:** Primarily known for its severe hepatotoxicity and cardiac arrhythmias. It is obsolete in modern practice and not specifically linked to postoperative shivering as a hallmark feature. * **C. Trichloroethylene:** An older analgesic/anesthetic agent known for causing cranial nerve palsies (especially the trigeminal nerve) if used with soda lime, but not typically associated with shivering. * **D. Ether:** While it causes a long recovery period and significant nausea/vomiting, it does not depress the thermoregulatory center as profoundly as Halothane, making shivering less characteristic. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment:** Postoperative shivering is most effectively treated with **Intravenous Pethidine** (Meperidine), which lowers the shivering threshold. * **Halothane Hepatitis:** A rare but serious idiosyncratic reaction (more common in adults/obese patients). * **Malignant Hyperthermia:** Halothane is a known trigger; the treatment of choice is **Dantrolene**. * **Cardiac Effect:** Halothane sensitizes the myocardium to catecholamines, increasing the risk of arrhythmias.

Q: Which antiparkinsonian drug directly activates D2 receptors?

Pramipixole. **Explanation:** **Correct Option: A. Pramipexole** Pramipexole is a **non-ergot dopamine agonist**. Unlike Levodopa, which is a precursor that must be converted into dopamine, Pramipexole acts directly by stimulating dopamine receptors in the striatum. It has a high affinity for the **D2 receptor family** (specifically D2 and D3 subtypes). Direct agonists are particularly useful in Parkinson’s disease as they do not require functional presynaptic dopaminergic neurons to be effective and have a longer half-life than levodopa. **Incorrect Options:** * **B. Entacapone:** This is a peripheral **COMT (Catechol-O-methyltransferase) inhibitor**. It does not activate receptors directly; instead, it prevents the peripheral breakdown of Levodopa, increasing its bioavailability to the brain. * **C. Benserazide:** This is a **peripheral DOPA decarboxylase inhibitor**. It is administered with Levodopa (e.g., Madopar) to prevent its systemic conversion to dopamine, thereby reducing peripheral side effects like nausea and cardiac arrhythmias. * **D. Selegiline:** This is a selective **MAO-B (Monoamine Oxidase-B) inhibitor**. It works by inhibiting the intracerebral degradation of dopamine, thus prolonging the action of endogenous or levodopa-derived dopamine. **High-Yield Clinical Pearls for NEET-PG:** * **Dopamine Agonists:** Divided into Ergot derivatives (Bromocriptine, Cabergoline—linked to cardiac valvular fibrosis) and Non-ergot derivatives (Pramipexole, Ropinirole, Rotigotine). * **Side Effects:** Dopamine agonists are notorious for causing **impulse control disorders** (pathological gambling, hypersexuality) and sudden "sleep attacks." * **Drug of Choice:** Pramipexole is often preferred in younger patients to delay the start of Levodopa therapy and minimize motor fluctuations (the "levodopa-sparing" strategy).

Q: Which of the following statements is NOT true about fosphenytoin?

It is lipid-soluble. ### Explanation **Fosphenytoin** is a water-soluble phosphate ester prodrug of phenytoin, specifically designed to overcome the pharmaceutical limitations of intravenous (IV) phenytoin. **1. Why "It is lipid-soluble" is the correct (NOT true) statement:** Unlike phenytoin, which is highly lipid-soluble and requires a propylene glycol solvent (causing pain and phlebitis), **fosphenytoin is highly water-soluble**. This property allows it to be dissolved in standard IV fluids (Normal Saline or Dextrose) and administered rapidly without the risk of local tissue necrosis or "Purple Glove Syndrome." **2. Analysis of Incorrect Options:** * **A. Used for GTCS:** Fosphenytoin is FDA-approved for the control of generalized tonic-clonic status epilepticus and for the prevention/treatment of seizures during neurosurgery. * **B. It is a prodrug of phenytoin:** After parenteral administration, fosphenytoin is rapidly converted by **phosphatases** in the blood and liver into active phenytoin. * **D. It is highly protein-bound:** Fosphenytoin is extensively bound (approx. 95-99%) to human plasma proteins, primarily albumin. It can displace phenytoin from binding sites, which is clinically significant during the conversion process. **3. NEET-PG High-Yield Clinical Pearls:** * **Dosing:** Fosphenytoin is prescribed in **Phenytoin Equivalents (PE)**. 1.5 mg of fosphenytoin = 1 mg of phenytoin. * **Administration:** It can be given **Intramuscularly (IM)**, whereas phenytoin cannot (due to erratic absorption and tissue damage). * **Safety Profile:** It has a lower risk of cardiac arrhythmias and local irritation compared to phenytoin, though rapid infusion can still cause hypotension. * **Advantage:** It can be infused 3 times faster than phenytoin (150 mg PE/min vs. 50 mg/min).

Q: Which of the following drugs has anxiolytic action with the least sedation?

Buspirone. ### Explanation **Correct Answer: A. Buspirone** **Mechanism and Rationale:** Buspirone is a unique anxiolytic agent that acts as a **selective partial agonist at the 5-HT1A receptors**. Unlike benzodiazepines, it does not interact with the GABA-A receptor complex. Because of its selective serotonergic mechanism, it lacks the sedative, hypnotic, anticonvulsant, and muscle-relaxant properties typical of other anxiolytics. It is the drug of choice for Generalized Anxiety Disorder (GAD) when the patient needs to remain alert (e.g., drivers, students). **Analysis of Incorrect Options:** * **B. Triazolam:** A short-acting benzodiazepine primarily used as a hypnotic for insomnia. It causes significant sedation and has a high risk of rebound insomnia. * **C. Alprazolam:** A potent benzodiazepine used for panic disorders and GAD. While effective, it causes dose-dependent sedation, psychomotor impairment, and carries a risk of dependence. * **D. Chlordiazepoxide:** A long-acting benzodiazepine used mainly for alcohol withdrawal. It has active metabolites that cause prolonged sedation and "hangover" effects. **High-Yield Clinical Pearls for NEET-PG:** * **"The 3 No’s" of Buspirone:** No Sedation, No Tolerance/Dependence (low abuse potential), and No interaction with Alcohol. * **Delayed Onset:** Unlike benzodiazepines, Buspirone takes **2–4 weeks** to show therapeutic effects; it is not useful for acute anxiety or panic attacks. * **Side Effects:** Most common side effects include dizziness, nausea, and headache. * **Metabolism:** It is metabolized by **CYP3A4**; its levels increase significantly if taken with grapefruit juice or rifampin.

Q: Which of the following analgesics should not be given in acute myocardial infarction?

Pentazocine. **Explanation:** The primary goal of analgesia in Acute Myocardial Infarction (AMI) is to relieve pain and reduce myocardial oxygen demand. **Why Pentazocine is contraindicated:** Pentazocine is an opioid agonist-antagonist (κ-agonist and μ-antagonist/partial agonist). It possesses **sympathomimetic properties**, which lead to an increase in plasma catecholamines. This results in an **increase in heart rate (tachycardia) and systemic blood pressure**, which significantly increases **myocardial oxygen demand**. In the setting of an AMI, where the heart is already ischemic, this can worsen the infarct size and increase the risk of arrhythmias. Furthermore, it can increase pulmonary artery pressure, increasing the workload on the right ventricle. **Analysis of other options:** * **Morphine:** This is the **drug of choice** for pain relief in AMI. It provides potent analgesia, reduces anxiety (anxiolytic), and has beneficial hemodynamic effects, such as venodilation (reducing preload) and modest arterial dilation (reducing afterload), thereby decreasing myocardial oxygen demand. * **Methadone:** A long-acting μ-opioid agonist. While not the first line for AMI due to its long half-life and risk of QTc prolongation, it does not possess the sympathomimetic "pressor" effects seen with pentazocine. * **Buprenorphine:** A partial μ-agonist. While it can be used for severe pain, it is generally avoided in AMI because its effects are difficult to reverse with Naloxone, but it does not carry the same high risk of increasing cardiac workload as pentazocine. **High-Yield Clinical Pearls for NEET-PG:** * **MONA** mnemonic for AMI: **M**orphine, **O**xygen, **N**itroglycerin, **A**spirin. * **Pentazocine** should also be avoided in patients with heart failure for the same hemodynamic reasons. * **Naloxone** is the specific antagonist for opioid overdose, but higher doses may be required to reverse buprenorphine.

Q: All the following statements regarding remifentanil are true EXCEPT?

Long acting anesthetic. Remifentanil is a unique, ultra-short-acting synthetic opioid analgesic used primarily in anesthesia. The correct answer is **D (Long acting anesthetic)** because remifentanil is characterized by its exceptionally short duration of action, not a long one [1]. **1. Why Option D is the correct answer (The Exception):** Remifentanil has a unique chemical structure containing an ester linkage. This allows it to undergo rapid hydrolysis by **non-specific tissue and plasma esterases**. Consequently, it has an ultra-short half-life (approximately 3–10 minutes) and a context-sensitive half-time that remains constant regardless of the duration of infusion [1]. This makes it the shortest-acting opioid available. **2. Analysis of Incorrect Options:** * **Option A (Useful for short painful procedures):** Due to its rapid onset and offset, it is ideal for procedures requiring intense analgesia for a brief period (e.g., intubation, brief surgeries) without prolonged respiratory depression. * **Option B (Metabolized by plasma esterases):** This is its defining pharmacokinetic feature. Unlike other opioids metabolized by the liver (CYP450), remifentanil metabolism is independent of hepatic or renal function. * **Option C (Equipotent as fentanyl):** Remifentanil and fentanyl are considered roughly equipotent in terms of analgesic strength, though remifentanil acts much faster and wears off sooner. **Clinical Pearls for NEET-PG:** * **Context-Sensitive Half-Time:** Remifentanil is the only opioid where this remains nearly constant (~3 mins) even after a 10-hour infusion. * **Organ-Independent Elimination:** It is the drug of choice for patients with end-stage liver or renal failure. * **Opioid-Induced Hyperalgesia:** Rapid withdrawal or high doses of remifentanil can sometimes lead to acute postoperative hyperalgesia. * **Mnemonic:** **R**emifentanil = **R**apidly metabolized by **R**BC/Plasma esterases.

Q: Epinephrine added to a solution of lignocaine for a peripheral nerve block will:

Increase the duration of action of the local anesthetic. ### Explanation **1. Why Option B is Correct:** Lignocaine is a local anesthetic (LA) that causes vasodilation at the site of injection. When **Epinephrine (Adrenaline)** is added, it acts on **$\alpha_1$-adrenergic receptors** to cause potent **vasoconstriction**. This results in: * **Decreased systemic absorption:** The LA remains at the nerve site for a longer period. * **Increased duration of action:** Since the drug is not washed away by the bloodstream quickly, the block lasts longer. * **Reduced systemic toxicity:** Slower absorption leads to lower peak plasma levels of the LA. * **Decreased bleeding:** Vasoconstriction provides a bloodless field for minor procedures. **2. Why Other Options are Incorrect:** * **Option A:** Epinephrine actually **decreases** the risk of convulsions. Convulsions are a sign of systemic CNS toxicity (due to high plasma levels of LA). By slowing systemic absorption, epinephrine keeps plasma levels low, thereby reducing the risk of CNS and cardiac toxicity. * **Option C:** Incorrect because the risk of convulsions is decreased, not increased. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Standard Concentration:** Epinephrine is typically added to LAs in a concentration of **1:200,000**. * **Contraindications:** Never use LA with Epinephrine for blocks in **"end-artery" areas** (fingers, toes, nose, ear lobules, and penis) as it can cause ischemia and **gangrene**. * **Hypertension/Cardiac Disease:** Use with caution in patients with uncontrolled hypertension or ischemic heart disease due to potential systemic effects of adrenaline. * **Felypressin:** An alternative vasoconstrictor (vasopressin analogue) sometimes used in dental anesthesia when epinephrine is contraindicated.

Question 1

Valproic acid is used in which of the following disorders?

Accepted Answer

Sydenham's chorea, Migraine, and Mania only

Answer

Sydenham's chorea and Mania only

Answer

Migraine and Obsessive compulsive disorder only

Answer

Migraine, Mania, and Obsessive compulsive disorder only

Question 2

What is the drug of choice for relapsing-remitting multiple sclerosis?

Accepted Answer

Beta interferon

Answer

Alpha interferon

Answer

Gamma interferon

Answer

Natalizumab

Question 3

All of the following statements about Phenytoin are true, except?

Accepted Answer

Stimulates insulin secretion

Answer

Follows saturation kinetics

Answer

Is teratogenic

Answer

Is highly protein bound

Question 4

"Shivering" is observed in the early postoperative period due to:

Accepted Answer

Halothane

Answer

Chloroform

Answer

Trichloroethylene

Answer

Ether

Question 5

Which antiparkinsonian drug directly activates D2 receptors?

Accepted Answer

Pramipixole

Answer

Entacapone

Answer

Benserazide

Answer

Selegiline

Question 6

Which of the following statements is NOT true about fosphenytoin?

Accepted Answer

It is lipid-soluble

Answer

Used for generalized tonic-clonic seizures (GTCS)

Answer

It is a prodrug of phenytoin

Answer

It is highly protein-bound

Question 7

Which of the following drugs has anxiolytic action with the least sedation?

Accepted Answer

Buspirone

Answer

Triazolam

Answer

Alprazolam

Answer

Chlordiazepoxide

Question 8

Which of the following analgesics should not be given in acute myocardial infarction?

Accepted Answer

Pentazocine

Answer

Methadone

Answer

Morphine

Answer

Buprenorphine

Question 9

All the following statements regarding remifentanil are true EXCEPT?

Accepted Answer

Long acting anesthetic

Answer

Useful for short painful procedures

Answer

Metabolized by plasma esterases

Answer

Equipotent as fentanyl

Question 10

Epinephrine added to a solution of lignocaine for a peripheral nerve block will:

Accepted Answer

Increase the duration of action of the local anesthetic

Answer

Increase risk of convulsions

Answer

Both increase risk of convulsions and increase the duration of action of the local anesthetic

Answer

None of these

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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