Central Nervous System Pharmacology Practice Questions

Q: Which of the following local anesthetics causes the least vasodilation?

Prilocaine. **Explanation:** Most local anesthetics (LAs) possess inherent **vasodilatory** properties at clinical concentrations. This occurs due to the relaxation of vascular smooth muscle, which increases local blood flow, leading to faster systemic absorption and a shorter duration of action. **1. Why Prilocaine is the Correct Answer:** Among the options provided, **Prilocaine** is unique because it causes the **least amount of vasodilation**. In fact, at low concentrations, it may even produce mild vasoconstriction. This characteristic results in slower systemic absorption compared to lignocaine, giving it a slightly longer duration of action and a lower risk of systemic toxicity (LAST) even without the addition of adrenaline. **2. Analysis of Incorrect Options:** * **Lignocaine (Lidocaine):** A potent vasodilator. It requires the addition of adrenaline (epinephrine) to counteract this effect, prolonging its duration and reducing surgical bleeding. * **Bupivacaine:** Also a significant vasodilator. While it is highly potent and long-acting due to lipid solubility, its vasodilatory effect contributes to its potential for cardiotoxicity if injected intravascularly. * **Ropivacaine:** While Ropivacaine is known to have some inherent vasoconstrictive properties (making it "safer" than bupivacaine), in comparative clinical studies regarding pure vasodilatory potential, **Prilocaine** is traditionally cited as having the least vasodilatory effect among the amide group. **High-Yield Clinical Pearls for NEET-PG:** * **Exceptions to the Rule:** While most LAs are vasodilators, **Cocaine** is the only local anesthetic that is a potent **vasoconstrictor** (due to inhibition of norepinephrine reuptake). * **Prilocaine & Methemoglobinemia:** A classic side effect of Prilocaine is the formation of methemoglobin (due to its metabolite *o-toluidine*). The treatment is **Methylene Blue**. * **Potency Order:** Bupivacaine > Ropivacaine > Lignocaine > Prilocaine.

Q: What is the drug of choice for petit mal seizures?

Valproate. **Explanation:** **Petit mal seizures**, also known as **Absence seizures**, are characterized by brief lapses in consciousness and a classic **3 Hz spike-and-wave pattern** on EEG. **1. Why Valproate is the Correct Choice:** While Ethosuximide is the drug of choice for *isolated* absence seizures [1], **Sodium Valproate** is considered the overall drug of choice for petit mal seizures in clinical practice and competitive exams like NEET-PG because: * It is a **broad-spectrum antiepileptic** effective against multiple seizure types [2]. * Absence seizures often coexist with Generalized Tonic-Clonic Seizures (GTCS) or Myoclonic seizures; Valproate covers all these [2], whereas Ethosuximide only covers absence seizures [1]. * **Mechanism:** It increases GABA levels, inhibits T-type $Ca^{2+}$ channels, and prolongs the inactivated state of $Na^+$ channels. **2. Why Other Options are Incorrect:** * **Ethosuximide (Option A):** It is the drug of choice for *pure* absence seizures (no other seizure types present) [1]. However, in a general context, Valproate is preferred due to its broader coverage. * **Carbamazepine (Option B) & Phenytoin (Option C):** These are narrow-spectrum agents [2]. Crucially, they are **contraindicated** in absence seizures as they can paradoxically **aggravate** or worsen petit mal attacks. **3. High-Yield Clinical Pearls for NEET-PG:** * **DOC for Pure Absence:** Ethosuximide [1] (Mechanism: Blocks T-type $Ca^{2+}$ channels in thalamic neurons). * **DOC for Atypical Absence/Myoclonic/GTCS:** Valproate [2]. * **Teratogenicity:** Valproate is highly teratogenic (Neural Tube Defects); avoid in pregnancy if possible. * **EEG Hallmark:** 3 Hz spike-and-wave discharge is the pathognomonic finding for Absence seizures.

Q: Thrombocytopenia is a known side effect of which of the following drugs?

Valproate. **Explanation:** **Valproate (Sodium Valproate/Valproic Acid)** is the correct answer. It is a broad-spectrum anti-epileptic drug also used as a first-line mood stabilizer in Bipolar Disorder. **Why Valproate causes Thrombocytopenia:** Valproate-induced thrombocytopenia is a well-documented, dose-dependent side effect. The underlying mechanism involves both **bone marrow suppression** (inhibiting megakaryocytopoiesis) and the production of **anti-platelet antibodies** (peripheral destruction). Clinically, this necessitates regular monitoring of Complete Blood Counts (CBC), especially before surgery or when used at high serum concentrations (>100 μg/mL). **Analysis of Incorrect Options:** * **Clonazepam:** A benzodiazepine used for anxiety and seizures. Its primary side effects are sedation, ataxia, and cognitive impairment; it does not typically cause hematological toxicity. * **Aripiprazole:** An atypical antipsychotic (partial D2 agonist). Common side effects include akathisia and insomnia. It is generally "metabolically neutral" and rarely associated with blood dyscrasias. * **Amisulpride:** An atypical antipsychotic (D2/D3 antagonist). Its most significant side effect is **hyperprolactinemia**; it is not known for causing thrombocytopenia. **High-Yield Clinical Pearls for NEET-PG:** * **Valproate Side Effects (Mnemonic: VALPROATE):** **V**omiting, **A**lopecia (curly hair), **L**iver toxicity (Hepatotoxicity), **P**ancreatitis, **R**etention of weight (Obesity), **O**edema, **A**norexia, **T**hrombocytopenia, **E**ncephalopathy (due to hyperammonemia). * **Teratogenicity:** Valproate is highly teratogenic, causing **Neural Tube Defects** (Spina Bifida). * **Drug of Choice:** It is the drug of choice for Myoclonic seizures and Bipolar Affective Disorder (Manic episodes).

Q: Which of the following local anesthetics is NOT used as a surface anesthetic?

Bupivacaine. **Explanation:** Local anesthetics (LAs) are classified based on their ability to penetrate mucous membranes and skin. To be effective as a **surface (topical) anesthetic**, a drug must have high lipid solubility and the ability to penetrate intact or broken surfaces to reach nerve endings. **Why Bupivacaine is the Correct Answer:** Bupivacaine is a potent, long-acting amide local anesthetic. However, it has **poor penetrative capacity** through mucous membranes and skin. Therefore, it is ineffective as a surface anesthetic. Its clinical utility is strictly limited to infiltration, nerve blocks, epidural, and spinal anesthesia. **Analysis of Incorrect Options:** * **Lidocaine:** The most versatile LA. It has excellent penetrative power and is used topically as a jelly (for catheterization), spray (for intubation), or ointment. * **Tetracaine:** An ester LA with high lipid solubility and potency. It is widely used as a surface anesthetic, particularly in ophthalmology (eye drops) and for spinal anesthesia. * **Cocaine:** The only naturally occurring LA. It has intrinsic vasoconstrictor properties and is an excellent surface anesthetic, historically used for ENT procedures. **NEET-PG High-Yield Pearls:** * **Surface Anesthetics:** Include Lidocaine, Tetracaine, Cocaine, Benzocaine, and Proparacaine. * **Non-Surface Anesthetics:** Include Bupivacaine, Procaine, and Chloroprocaine (these are poorly absorbed topically). * **Bupivacaine Toxicity:** It is highly **cardiotoxic** (blocks cardiac sodium channels during diastole). Intravenous lipid emulsion (20%) is the antidote for systemic toxicity. * **EMLA Cream:** A eutectic mixture of Lidocaine and Prilocaine used for topical anesthesia on intact skin.

Q: Which antiparkinsonian drug is known to cause cardiac valvular fibrosis?

Pergolide. **Explanation:** The correct answer is **Pergolide**. **1. Why Pergolide is correct:** Pergolide is an older, **ergot-derived** dopamine receptor agonist. The mechanism behind cardiac valvular fibrosis is its high affinity and potent agonist activity at the **5-HT2B receptors** located on heart valves. Activation of these receptors stimulates fibroblast proliferation, leading to valvulopathy (similar to the pathology seen in Carcinoid syndrome). Due to this serious adverse effect, pergolide was voluntarily withdrawn from the US market and its use is severely restricted worldwide. **2. Why the other options are incorrect:** * **Levodopa (A):** A precursor to dopamine. Its primary side effects are peripheral (nausea, arrhythmias, orthostatic hypotension) and central (dyskinesias, hallucinations), but it does not cause valvular fibrosis. * **Ropinirole (B) & Pramipexole (C):** These are **non-ergot** dopamine agonists. Unlike ergot derivatives, they are highly selective for D2/D3 receptors and have negligible affinity for 5-HT2B receptors. Therefore, they do not carry the risk of cardiac fibrosis and are preferred in clinical practice. **3. NEET-PG High-Yield Pearls:** * **Ergot-derived drugs** associated with fibrosis (cardiac, pulmonary, or retroperitoneal) include **Pergolide, Cabergoline, and Methysergide**. * **Bromocriptine** is also an ergot derivative but has a much lower risk of valvulopathy compared to Pergolide. * **Pramipexole** is unique as it may have neuroprotective properties by scavenging free radicals. * **Apomorphine** is the dopamine agonist used as a "rescue" therapy for "off" episodes in Parkinson’s disease (administered SC).

Q: Which of the following drugs is used as a transdermal patch for Parkinson's disease?

Rotigotine. Rotigotine is a non-ergot dopamine agonist (specifically acting on D3, D2, and D1 receptors). It is unique because it is formulated as a **transdermal patch** designed for once-daily application. This delivery system provides continuous drug delivery (continuous dopaminergic stimulation), which helps maintain stable plasma levels and reduces the "off" periods associated with fluctuating levels of oral medications.Analysis of Incorrect Options: * **Levodopa (A):** The gold standard for Parkinson’s, but it is administered orally (often with carbidopa) [1] or as an intestinal gel (Duopa). It is not available as a patch due to its high dosage requirements and transport characteristics. * **Selegiline (C):** While Selegiline is available as a transdermal patch (Emsam), it is FDA-approved in that form specifically for **Major Depressive Disorder**, not Parkinson’s disease. For Parkinson's, it is used orally as an MAO-B inhibitor. * **Carbidopa (D):** This is a peripheral dopa-decarboxylase inhibitor used solely to prevent the peripheral metabolism of Levodopa. It has no antiparkinsonian effect on its own and is not used as a patch.High-Yield Clinical Pearls for NEET-PG: * **Dopamine Agonists:** Rotigotine, Pramipexole, and Ropinirole are preferred in younger patients to delay the start of Levodopa. * **Side Effects:** Like other dopamine agonists, Rotigotine can cause impulse control disorders (pathological gambling, hypersexuality) [1, 2] and sudden sleep attacks. * **Apomorphine:** Another non-oral dopamine agonist, used via subcutaneous injection for "rescue" therapy during acute off-episodes. * **Patch Site:** Rotigotine patches should be rotated daily to avoid skin irritation; the same site should not be used more than once every 14 days.

Q: Which drug has been found to be beneficial in amyotrophic lateral sclerosis?

Riluzole. **Explanation:** **Amyotrophic Lateral Sclerosis (ALS)** is a progressive neurodegenerative disease involving both upper and lower motor neurons. The pathogenesis is linked to **glutamate excitotoxicity**, where excessive glutamate leads to overstimulation of NMDA receptors, resulting in neuronal calcium overload and cell death. **Why Riluzole is the Correct Answer:** **Riluzole** is a glutamate antagonist. It works by: 1. Inhibiting presynaptic glutamate release. 2. Inactivating voltage-dependent sodium channels. 3. Interfering with intracellular events following transmitter binding. Clinical trials have shown that Riluzole modestly prolongs survival (by approximately 2–3 months) and delays the need for tracheostomy in ALS patients. **Why the Other Options are Incorrect:** * **B. Methylprednisolone:** While inflammation occurs in ALS, corticosteroids like methylprednisolone have shown no clinical benefit in slowing disease progression. They are primarily used in acute relapses of Multiple Sclerosis. * **C. Hydroxyurea:** This is a ribonucleotide reductase inhibitor used in Sickle Cell Anemia (to increase HbF) and Chronic Myeloid Leukemia. It has no role in treating motor neuron diseases. **High-Yield Clinical Pearls for NEET-PG:** * **Edaravone:** Another FDA-approved drug for ALS; it acts as a **free radical scavenger** (antioxidant) to reduce oxidative stress. * **Side effects of Riluzole:** Most common are nausea, weakness, and **elevated liver enzymes** (ALT/AST), necessitating regular LFT monitoring. * **Symptomatic Management in ALS:** * Spasticity: Baclofen or Tizanidine. * Sialorrhea (Drooling): Glycopyrrolate or Atropine.

Q: Which of the following adverse effects is characteristically associated with methysergide?

Retroperitoneal fibrosis. **Explanation:** **Methysergide** is an ergot alkaloid and a potent 5-HT₂ receptor antagonist formerly used for the prophylaxis of migraine and cluster headaches. **Why Retroperitoneal Fibrosis is Correct:** The most characteristic and serious adverse effect of long-term methysergide therapy is **retroperitoneal fibrosis**. This condition involves the proliferation of dense fibrous tissue in the retroperitoneum, which can obstruct the ureters, leading to hydronephrosis and renal failure. It is also associated with similar fibrotic changes in the pleura (**pleuropulmonary fibrosis**) and the endocardium (**subendocardial fibrosis/valvular heart disease**). The mechanism is thought to be related to its serotonergic activity, which can stimulate fibroblast proliferation. **Analysis of Incorrect Options:** * **A. Pulmonary hypertension:** While some serotonergic drugs (like fenfluramine) are linked to pulmonary hypertension, methysergide is specifically known for pleuropulmonary fibrosis rather than primary vascular hypertension. * **C. Hepatotoxicity:** Methysergide is not typically associated with significant liver injury; its toxicity profile is dominated by fibrotic and vascular complications. * **D. Ischemic heart disease:** While ergot alkaloids can cause vasoconstriction, the "hallmark" chronic toxicity of methysergide is fibrosis, not acute coronary syndrome. **High-Yield Clinical Pearls for NEET-PG:** 1. **Drug Holidays:** To prevent fibrotic complications, methysergide requires a mandatory "drug-free interval" of 3–4 weeks every 6 months. 2. **Withdrawal:** It must be tapered slowly to avoid rebound headaches. 3. **Current Status:** Due to these severe fibrotic risks, methysergide has been largely replaced by safer alternatives like Beta-blockers, Topiramate, or Valproate.

Q: A patient is prescribed a first-generation antihistamine. What should they be advised to avoid?

Driving a motor vehicle. **Explanation:** **1. Why Option A is Correct:** First-generation antihistamines (e.g., Diphenhydramine, Chlorpheniramine, Promethazine) are highly **lipophilic** and readily cross the **blood-brain barrier (BBB)**. Once in the CNS, they antagonize H1 receptors, which are essential for maintaining wakefulness and alertness. This results in significant **sedation**, drowsiness, and impaired psychomotor performance. Patients are strictly advised to avoid driving or operating heavy machinery to prevent accidents due to delayed reaction times. **2. Why Other Options are Incorrect:** * **Option B (Cheese):** Avoiding tyramine-rich foods like aged cheese is a specific precaution for patients on **MAO inhibitors** (to prevent hypertensive crisis), not antihistamines. * **Option C (Strenuous Exercise):** While antihistamines have mild anticholinergic effects that can slightly decrease sweating, there is no absolute contraindication for exercise. This precaution is more relevant for drugs causing severe heat intolerance or significant beta-blockade. **3. NEET-PG High-Yield Clinical Pearls:** * **Mechanism of Sedation:** First-generation H1 blockers are non-selective and have high affinity for central H1 receptors. Second-generation agents (e.g., Cetirizine, Loratadine) are polar, have low lipid solubility, and are substrates for **P-glycoprotein efflux pumps**, making them "non-sedating." * **Anticholinergic Side Effects:** First-generation agents also block muscarinic receptors, leading to "dry" symptoms: dry mouth, blurred vision, urinary retention, and constipation. * **Paradoxical Excitation:** In children, toxic doses of these drugs can sometimes cause CNS stimulation and seizures rather than sedation. * **Drug Interaction:** They potentiate the effects of other CNS depressants, including alcohol and benzodiazepines.

Question 1

Which of the following local anesthetics causes the least vasodilation?

Accepted Answer

Prilocaine

Answer

Bupivacaine

Answer

Ropivacaine

Answer

Lignocaine

Question 2

What is the drug of choice for petit mal seizures?

Accepted Answer

Valproate

Answer

Ethosuximide

Answer

Carbamazepine

Answer

Phenytoin

Question 3

Thrombocytopenia is a known side effect of which of the following drugs?

Accepted Answer

Valproate

Answer

Clonazepam

Answer

Aripiprazole

Answer

Amisulpride

Question 4

Which of the following local anesthetics is NOT used as a surface anesthetic?

Accepted Answer

Bupivacaine

Answer

Lidocaine

Answer

Tetracaine

Answer

Cocaine

Question 5

Which antiparkinsonian drug is known to cause cardiac valvular fibrosis?

Accepted Answer

Pergolide

Answer

Levodopa

Answer

Ropinirole

Answer

Pramipexole

Question 6

Which of the following drugs is used as a transdermal patch for Parkinson's disease?

Accepted Answer

Rotigotine

Answer

Levodopa

Answer

Selegiline

Answer

Carbidopa

Question 7

Which drug has been found to be beneficial in amyotrophic lateral sclerosis?

Accepted Answer

Riluzole

Answer

Methylprednisolone

Answer

Hydroxyurea

Answer

None of the above

Question 8

Which of the following adverse effects is characteristically associated with methysergide?

Accepted Answer

Retroperitoneal fibrosis

Answer

Pulmonary hypertension

Answer

Hepatotoxicity

Answer

Ischemic heart disease

Question 9

A patient is prescribed a first-generation antihistamine. What should they be advised to avoid?

Accepted Answer

Driving a motor vehicle

Answer

Consuming cheese

Answer

Engaging in strenuous physical exercise

Answer

All of the above

Question 10

Varenicline is used in which of the following conditions?

Accepted Answer

Nicotine dependency

Answer

Pulmonary hemosiderosis

Answer

Sleep apnea

Answer

Alpha-1-antitrypsin deficiency

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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