Central Nervous System Pharmacology Practice Questions

Q: Which of the following drugs are used for the prophylaxis of migraine?

All of these. Migraine management is divided into **Abortive (Acute)** therapy and **Prophylactic (Preventive)** therapy. Prophylaxis is indicated if attacks occur >2–3 times per month, are severe, or if acute treatments are contraindicated. ### Explanation of Options: * **Beta-blockers (e.g., Propranolol):** These are the **first-line** drugs for migraine prophylaxis. They likely work by stabilizing vascular tone and inhibiting cortical spreading depression. Propranolol is the most commonly used agent in this class. * **Flunarizine:** This is a **selective calcium channel blocker** (specifically T-type and L-type). Unlike verapamil, flunarizine is highly effective in reducing the frequency and severity of migraine attacks, though it may cause weight gain and sedation. * **Sodium Valproate:** This **anti-epileptic** drug is an effective prophylactic agent. It works by increasing GABAergic inhibition and modulating excitatory neurotransmitters. Topiramate is another anti-epileptic frequently used for this purpose. Since all three classes—Beta-blockers, Calcium channel blockers, and Anti-epileptics—are established prophylactic agents, **Option D (All of these)** is correct. ### High-Yield Clinical Pearls for NEET-PG: * **DOC for Prophylaxis:** Propranolol (avoid in asthmatics and diabetics). * **DOC for Acute Attack:** Sumatriptan (5-HT$_{1B/1D}$ agonist). * **Tricyclic Antidepressants (TCAs):** Amitriptyline is the preferred prophylactic agent for patients with co-existing tension-type headaches, depression, or insomnia. * **Newer Agents:** **CGRP Antagonists** (e.g., Erenumab) are used for prophylaxis in refractory cases. * **Menstrual Migraine:** Frovatriptan or Naproxen are often used for short-term prophylaxis.

Q: All are side effects of phenytoin, EXCEPT?

Hypoglycemia. Phenytoin is a high-yield topic in NEET-PG due to its narrow therapeutic index and diverse side-effect profile. ### **Explanation of the Correct Answer** **B. Hypoglycemia:** This is the correct answer because Phenytoin actually causes **Hyperglycemia**, not hypoglycemia. Phenytoin inhibits the release of insulin from the pancreas (by stabilizing membranes and reducing calcium influx). This can lead to elevated blood glucose levels and, in some cases, glycosuria. ### **Analysis of Incorrect Options** * **A. Ataxia:** This is a dose-dependent sign of cerebellar toxicity. Along with nystagmus and diplopia, ataxia is one of the earliest signs that phenytoin levels have exceeded the therapeutic range (usually >20 µg/ml). * **C. Hirsutism:** This is a common non-dose-dependent side effect, particularly problematic in young females. It involves the growth of unwanted hair on the face and body. * **D. Gum Hypertrophy:** Also known as gingival hyperplasia, this occurs in about 20% of patients. It is caused by the overgrowth of gingival tissue due to increased fibroblast proliferation and collagen deposition. ### **Clinical Pearls for NEET-PG** To remember the side effects of Phenytoin, use the mnemonic **"HOT MALAI"**: * **H** – Hirsutism, Hypertrophy of gums, Hyperglycemia * **O** – Osteomalacia (due to induced Vitamin D metabolism) * **T** – Teratogenicity (**Fetal Hydantoin Syndrome**: cleft lip/palate, microcephaly) * **M** – Megaloblastic anemia (due to folate interference) * **A** – Ataxia * **L** – Lymphadenopathy (Pseudolymphoma) * **A** – Arrhythmias (when given via rapid IV push) * **I** – Insulin inhibition (leading to Hyperglycemia) **Key Fact:** Phenytoin follows **Zero-order kinetics** (capacity-limited metabolism) at therapeutic or high concentrations, making small dose increases lead to disproportionate rises in plasma levels.

Q: All of the local anesthetics given below are amides, EXCEPT:

Procaine. Local anesthetics (LAs) are chemically classified into two main groups based on the intermediate chain linking the aromatic ring and the amino group: **Amides** and **Esters**. ### 1. Why Procaine is the Correct Answer **Procaine** is an **Ester**-type local anesthetic. Esters are metabolized by plasma pseudocholinesterase and are more likely to cause allergic reactions due to the formation of para-aminobenzoic acid (PABA). **The "i" Rule (Mnemonic):** To differentiate between the two classes for exams: * **Amides** have **two** "i"s in their name (e.g., L**i**doca**i**ne). * **Esters** have only **one** "i" in their name (e.g., Proca**i**ne). ### 2. Analysis of Incorrect Options * **A. Lignocaine (Lidocaine):** An amide. It is the most commonly used LA and serves as the prototype amide. * **C. Prilocaine:** An amide. It is known for causing methemoglobinemia at high doses due to its metabolite, o-toluidine. * **D. Etidocaine:** An amide. It is a long-acting agent characterized by a profound motor block. ### 3. Clinical Pearls for NEET-PG * **Metabolism:** Amides are metabolized in the **liver** (by CYP450 enzymes), while Esters are metabolized in the **plasma** (by pseudocholinesterase). * **Cocaine** is the only naturally occurring ester and the only LA that causes **vasoconstriction** (others are vasodilators). * **Bupivacaine** is the most cardiotoxic LA; **Levobupivacaine** and **Ropivacaine** are safer S-enantiomer alternatives. * **Benzocaine** is an ester used topically; it is also a common cause of methemoglobinemia.

Q: Peripheral vasospasm is an adverse effect of which drug?

Bromocriptine. **Explanation:** The correct answer is **Bromocriptine**. **1. Why Bromocriptine is correct:** Bromocriptine is a first-generation **Ergot-derivative** dopamine agonist. Ergot derivatives are notorious for causing potent vasoconstriction due to their partial agonist activity on alpha-adrenergic receptors and serotonin receptors. This leads to **peripheral vasospasm**, which can manifest clinically as **Raynaud’s phenomenon** or digital ischemia. Long-term use of ergot derivatives is also associated with fibrotic complications (pleuropulmonary, cardiac, and retroperitoneal fibrosis). **2. Why the other options are incorrect:** * **Ropinirole and Pramipexole (Options A & D):** These are **Non-ergot** dopamine agonists. They are highly selective for D2 and D3 receptors and lack the ergot-ring structure. Consequently, they do not cause peripheral vasospasm or systemic fibrosis. Their common side effects include nausea, orthostatic hypotension, and impulse control disorders (e.g., pathological gambling). * **Levodopa (Option B):** As a precursor to dopamine, Levodopa primarily causes peripheral side effects like nausea and cardiac arrhythmias (due to peripheral conversion to catecholamines) or central effects like dyskinesias and hallucinations. It does not cause vasospasm. **3. NEET-PG High-Yield Pearls:** * **Ergot-derivatives:** Bromocriptine, Cabergoline, Pergolide (associated with vasospasm and fibrosis). * **Non-ergot derivatives:** Ropinirole, Pramipexole, Rotigotine, Apomorphine (preferred in younger patients to delay Levodopa use). * **Clinical Sign:** If a patient on Bromocriptine complains of cold, blue fingers in response to cold (Raynaud’s), the drug should be switched to a non-ergot agonist. * **Erythromelalgia:** Paradoxically, Bromocriptine can also cause this condition (red, painful, swollen extremities), though vasospasm is more characteristic of the ergot class.

Q: Tolcapone is known for which of the following toxicities?

Hepatotoxicity. **Explanation:** **Tolcapone** is a COMT (Catechol-O-methyltransferase) inhibitor used as an adjunct to Levodopa/Carbidopa therapy in Parkinson’s disease [1]. Its primary mechanism is to inhibit the peripheral and central breakdown of Levodopa, thereby increasing its bioavailability and duration of action [2]. **Why Hepatotoxicity is the Correct Answer:** The most significant and dose-limiting adverse effect of Tolcapone is **fulminant hepatic failure** [1]. Due to this risk of severe hepatotoxicity, it is generally reserved for patients who do not respond to other treatments. Patients on Tolcapone require mandatory, periodic monitoring of liver function tests (LFTs). This is in contrast to **Entacapone**, another COMT inhibitor, which is not associated with hepatotoxicity and is more commonly used in clinical practice [2]. **Why Other Options are Incorrect:** * **Ototoxicity:** This is typically associated with drugs like Aminoglycosides, Loop diuretics, or Cisplatin. Tolcapone has no known effect on the auditory system. * **Nephrotoxicity:** While many drugs are cleared renally, Tolcapone does not cause direct structural or functional damage to the kidneys. Common nephrotoxic agents include NSAIDs, Amphotericin B, and Contrast media. **High-Yield Clinical Pearls for NEET-PG:** * **Tolcapone vs. Entacapone:** Tolcapone acts both **peripherally and centrally**, whereas Entacapone acts only **peripherally** [1][2]. * **Orange Discoloration:** Both drugs can cause a harmless orange discoloration of urine. * **The "3 Ls" of Tolcapone:** **L**iver toxicity, **L**onger duration of action (compared to Entacapone), and **L**evodopa-sparing effect. * **Monitoring:** If no clinical improvement is seen within 3 weeks, Tolcapone should be discontinued due to the risk-benefit ratio regarding the liver.

Q: What is the most common drug used for prophylaxis of migraine?

Propranolol. **Explanation:** **Propranolol** is considered the **first-line drug of choice** for the continuous prophylaxis of migraine. It is a non-selective beta-blocker that works by stabilizing vascular tone, reducing central catecholaminergic hyperactivity, and inhibiting the cortical spreading depression (CSD) associated with migraine pathophysiology. It is particularly effective in patients with co-existing hypertension or anxiety. **Analysis of Options:** * **A. Sumatriptan:** This is a 5-HT$_{1B/1D}$ receptor agonist used for the **acute treatment** of migraine attacks to abort the headache. It is never used for prophylaxis because frequent use can lead to "medication overuse headache." * **C. Valproate:** While sodium valproate is an effective prophylactic agent (especially for patients with comorbid epilepsy), it is generally considered a second-line option due to its side-effect profile (weight gain, hair loss, and teratogenicity). * **D. Flunarizine:** This is a calcium channel blocker used for prophylaxis, particularly in Europe and India. However, due to its side effects (sedation and weight gain) and slower onset of action, it is usually not the first choice over beta-blockers. **High-Yield Clinical Pearls for NEET-PG:** * **Prophylaxis Criteria:** Indicated if attacks occur $>2-3$ times per month or are severely disabling. * **Contraindications for Propranolol:** Avoid in patients with bronchial asthma, heart block, or peripheral vascular disease (Raynaud’s). * **Other Prophylactic Agents:** Amitriptyline (DOC if comorbid depression/insomnia), Topiramate (DOC if the patient is obese, as it causes weight loss), and CGRP antagonists (e.g., Erenumab) for refractory cases. * **DOC in Pregnancy:** Magnesium or low-dose Propranolol (though lifestyle changes are preferred). Avoid Valproate (Category X for migraine).

Q: Which of the following statements regarding morphine is NOT true?

It is used in the management of angina pectoris.. The correct answer is **B**, as Morphine is **not** typically used in the management of stable or unstable angina pectoris. **1. Why Option B is the correct (False) statement:** While Morphine is a potent analgesic, it is not a first-line or standard treatment for **Angina Pectoris**. Angina is primarily managed with nitrates, beta-blockers, and calcium channel blockers to improve oxygen supply-demand balance. Morphine is reserved for pain that is unresponsive to nitrates, specifically in the context of an acute **Myocardial Infarction (MI)**. **2. Analysis of other options:** * **Option A (True):** Morphine is highly effective for **severe traumatic pain**, such as bone fractures, due to its potent action on $\mu$-opioid receptors in the CNS [1]. * **Option C (True):** Morphine is a cornerstone in **MI management** (MONA protocol: Morphine, Oxygen, Nitrates, Aspirin). It provides analgesia, reduces anxiety (anxiolysis), and acts as a venodilator, which decreases preload and myocardial oxygen demand [1]. * **Option D (True):** Morphine is **contraindicated in head injuries**. It causes respiratory depression, leading to $CO_2$ retention. $CO_2$ is a potent cerebral vasodilator, which increases cerebral blood flow and further elevates **Intracranial Pressure (ICP)**. It also causes miosis, which interferes with pupillary monitoring. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Morphine is the DOC for **Acute Left Ventricular Failure (Cardiac Asthma)** because it relieves air hunger and reduces preload [1]. * **Biliary Colic:** Morphine can aggravate biliary colic by causing spasm of the **Sphincter of Oddi** (Pethidine is often preferred here as it has less biliary spasm effect). * **Triad of Opioid Poisoning:** Pinpoint pupil, Respiratory depression, and Coma. * **Antidote:** Naloxone (Pure antagonist) [1].

Q: What is the first-line drug for absence seizures?

Valproate. **Explanation:** **1. Why Valproate is the Correct Answer:** Valproate (Sodium Valproate) is considered the first-line treatment for absence seizures, especially when they coexist with other seizure types like Generalized Tonic-Clonic Seizures (GTCS). Its mechanism involves multiple pathways: it inhibits T-type calcium channels in thalamic neurons (the hallmark of absence seizures), increases GABA levels, and blocks voltage-gated sodium channels. While **Ethosuximide** is also a first-line choice specifically for pure absence seizures, Valproate is often preferred in clinical practice and exams due to its broad-spectrum activity against multiple seizure types. **2. Why the Other Options are Incorrect:** * **Phenytoin (A) and Carbamazepine (D):** These are narrow-spectrum anticonvulsants that act primarily by blocking sodium channels. Crucially, they are **contraindicated** in absence seizures as they can paradoxically aggravate or precipitate absence attacks and myoclonic seizures. * **Benzodiazepines (B):** While drugs like Clonazepam are effective against absence seizures, they are generally reserved as second or third-line agents due to the development of tolerance and side effects like sedation. **3. Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC) Summary:** * Pure Absence Seizures: Ethosuximide (preferred in children to avoid hepatotoxicity). * Absence + GTCS: Valproate. * Myoclonic Seizures: Valproate. * **EEG Hallmark:** Absence seizures are characterized by a classic **3 Hz spike-and-wave pattern**. * **Teratogenicity:** Valproate is highly teratogenic (causes Neural Tube Defects); avoid in women of childbearing age if possible.

Question 1

Which of the following drugs are used for the prophylaxis of migraine?

Accepted Answer

All of these

Answer

Flunarizine

Answer

Beta blocker

Answer

Sodium valproate

Question 2

All are side effects of phenytoin, EXCEPT?

Accepted Answer

Hypoglycemia

Answer

Ataxia

Answer

Hirsutism

Answer

Gum hypertrophy

Question 3

All of the local anesthetics given below are amides, EXCEPT:

Accepted Answer

Procaine

Answer

Lignocaine

Answer

Prilocaine

Answer

Etidocaine

Question 4

Peripheral vasospasm is an adverse effect of which drug?

Accepted Answer

Bromocriptine

Answer

Ropinirole

Answer

Levodopa

Answer

Pramipexole

Question 5

Tolcapone is known for which of the following toxicities?

Accepted Answer

Hepatotoxicity

Answer

Ototoxicity

Answer

Nephrotoxicity

Answer

All of the above

Question 6

What is the most common drug used for prophylaxis of migraine?

Accepted Answer

Propranolol

Answer

Sumatriptan

Answer

Valproate

Answer

Flunarizine

Question 7

A patient on chronic drug treatment presents with gingival hyperplasia and facial hirsutism. Which drug is most likely responsible for these side-effects?

Accepted Answer

Phenytoin

Answer

Carbamazepine

Answer

Valproic acid

Answer

Phenobarbitone

Question 8

Which of the following statements regarding morphine is NOT true?

Accepted Answer

It is used in the management of angina pectoris.

Answer

It is used in the management of bone fractures.

Answer

It is used in the management of myocardial infarction.

Answer

It is not used in head injuries.

Question 9

Which of the following adverse effects of levodopa is not blocked by carbidopa?

Accepted Answer

Psychosis

Answer

Vomiting

Answer

Hypotension

Answer

Tachycardia

Question 10

What is the first-line drug for absence seizures?

Accepted Answer

Valproate

Answer

Phenytoin

Answer

Benzodiazepines

Answer

Carbamazepine

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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