Central Nervous System Pharmacology Practice Questions

Q: Which triptan is available in nasal spray form?

Sumatriptan. ***Sumatriptan*** - **Sumatriptan** is available in multiple formulations, including **oral, subcutaneous injection, and nasal spray**, making it versatile for migraine treatment [1], [2]. - The nasal spray formulation allows for **faster absorption** and onset of action, which can be beneficial for patients with nausea or vomiting during migraine attacks [1]. *Rizatriptan* - **Rizatriptan** is primarily available in **oral tablet** and **orally disintegrating tablet** (ODT) forms [2]. - It does not have a commonly available nasal spray formulation for migraine treatment [2]. *Naratriptan* - **Naratriptan** is available as an **oral tablet** and is known for its **longer half-life** and generally milder side effect profile compared to sumatriptan [2]. - It is not available in a nasal spray formulation [2]. *Frovatriptan* - **Frovatriptan** is available exclusively as an **oral tablet** and is notable for having the **longest half-life** among triptans, making it useful for preventing recurring migraines [2]. - There is no nasal spray formulation for frovatriptan [2].

Q: Where is the benzodiazepine binding site located on GABA receptors?

γ-subunit. ***γ-subunit*** - The **benzodiazepine binding site** is located at the interface between the **α and γ subunits** of the GABA-A receptor, with the **γ-subunit (especially γ2) being essential** for benzodiazepine sensitivity. - The presence of the **γ2 subunit** is **mandatory** for benzodiazepine binding - receptors lacking this subunit are **insensitive to benzodiazepines**. - Benzodiazepines bind to this site and act as **positive allosteric modulators**, increasing the frequency of **chloride channel opening** in response to GABA. - This is the **standard answer** for NEET-PG and medical PG examinations in India. *α-subunit* - The **α-subunit** contributes to forming the benzodiazepine binding pocket at the α-γ interface. - Different **α-subunit isoforms** (α1, α2, α3, α5) determine the pharmacological profile and tissue distribution of benzodiazepine effects. - However, the **α-subunit alone** cannot bind benzodiazepines without the γ-subunit. *β-subunit* - The **β-subunit** contains the primary binding site for **GABA** itself. - It does not participate in benzodiazepine binding but is crucial for the receptor's overall function and GABAergic signaling. *δ-subunit* - The **δ-subunit** replaces the γ-subunit in certain GABA-A receptor subtypes that mediate **tonic inhibition**. - Receptors containing **δ-subunits** are **insensitive to benzodiazepines** but sensitive to neurosteroids and certain general anesthetics. - This is a key distinguishing feature between phasic (γ-containing) and tonic (δ-containing) GABA-A receptors.

Q: What is the primary mechanism of action of zonisamide?

Sodium channels. ***Sodium channels (Correct Answer)*** - Zonisamide's primary mechanism involves **blocking voltage-sensitive sodium channels**, which stabilizes neuronal membranes and inhibits repetitive neuronal firing. - This action helps to prevent the propagation of **seizure activity** in the brain. *GABA receptors* - While zonisamide has some weak effects on GABA, it is not its **primary mechanism of action** for antiepileptic efficacy. - Drugs like **benzodiazepines** and **barbiturates** primarily act by enhancing GABAergic transmission. *T-type calcium channels* - Zonisamide also blocks T-type calcium channels, contributing to its broad-spectrum antiepileptic activity, but this is a **secondary mechanism** compared to its sodium channel blockade. - **Ethosuximide** is a classic example of a drug primarily acting on T-type calcium channels, especially for absence seizures. *Cl- channels* - Zonisamide does not primarily act on **chloride channels**; these are often modulated by GABA receptors. - Drugs that act directly on chloride channels are not typically used as **antiepileptics** in the same way.

Q: What effect does morphine have on muscle tone?

Increased muscle tone. ***Increased muscle tone*** - Morphine **increases skeletal muscle tone** and can cause muscle rigidity, particularly with rapid IV administration (truncal rigidity). - It significantly increases **smooth muscle tone** in various organs including the sphincter of Oddi (causing biliary colic), bladder sphincter (causing urinary retention), and GI tract (causing constipation). - This increased tone in sphincters and smooth muscle is a well-documented effect mediated through **opioid receptor activation**. *Bradycardia (not increased heart rate)* - Morphine typically causes **bradycardia** (decreased heart rate) due to vagal stimulation and central effects, not tachycardia. - Increased heart rate would be atypical and not a primary pharmacological effect of morphine. *Miosis (not mydriasis)* - Morphine characteristically causes **miosis** (pinpoint pupils) due to stimulation of the Edinger-Westphal nucleus of the oculomotor nerve. - Mydriasis (dilated pupils) is seen with anticholinergics or sympathomimetics, not opioids. *Respiratory depression (not stimulation)* - Morphine causes **respiratory depression**, not stimulation, by reducing the responsiveness of brainstem respiratory centers to CO2. - This is one of the most dangerous adverse effects and the primary cause of death in opioid overdose.

Q: What is the classification of Lorcaserin?

Anti-obesity. ***Anti-obesity*** - Lorcaserin is a selective **serotonin 5-HT₂C receptor agonist** that works by promoting satiety and reducing food intake. - It is prescribed as a long-term treatment for **weight management** in adults who are obese or overweight with at least one weight-related comorbidity. *Anti-anxiety* - Anti-anxiety medications, such as **benzodiazepines** or **SSRIs**, primarily target neurotransmitters like GABA or serotonin 5-HT₁A receptors to reduce anxiety symptoms. - Lorcaserin's primary mechanism of action is distinct, focusing on the 5-HT₂C receptor for appetite regulation, not anxiety. *Anti-smoking* - Anti-smoking medications, like **varenicline** or **bupropion**, are designed to reduce nicotine cravings and withdrawal symptoms. - Their mechanisms often involve nicotinic acetylcholine receptors or dopamine and norepinephrine reuptake inhibition, which differs from lorcaserin's action. *Anti-helminthic* - Anti-helminthic drugs are used to treat **parasitic worm infections** by paralyzing or killing the worms. - Common examples include **albendazole** or **mebendazole**, which have no relation to appetite control or obesity treatment.

Q: Which local anaesthetic is known to cause methemoglobinemia?

Prilocaine. ***Prilocaine*** - **Prilocaine** is metabolized into **ortho-toluidine**, which can oxidize hemoglobin to **methemoglobin**, especially at higher doses or in susceptible individuals. - **Methemoglobinemia** symptoms include **cyanosis**, **dyspnea**, and in severe cases, central nervous system depression, due to reduced oxygen-carrying capacity of blood. *Procaine* - **Procaine** is an ester-type local anesthetic. It is metabolized to **para-aminobenzoic acid (PABA)**, which can cause allergic reactions, but it is not associated with methemoglobinemia. - It has a relatively **short duration of action** and is less commonly used now compared to amide-type local anesthetics. *Etidocaine* - **Etidocaine** is an amide-type local anesthetic that is known for its **long duration of action** and high potency. - While it can cause systemic toxicity with high doses due to its cardiac and neurological effects, **methemoglobinemia** is not a characteristic side effect. *Ropivacaine* - **Ropivacaine** is an amide-type local anesthetic similar to bupivacaine, known for its **motor-sparing effect** and use in regional anesthesia. - It is associated with a lower risk of **cardiotoxicity** compared to bupivacaine but does not cause methemoglobinemia.

Q: Which anaesthetic belongs to the ester group?

Procaine. ***Procaine*** - **Procaine** is a classical **ester-type** local anesthetic, characterized by an ester linkage between the aromatic and amine parts of its chemical structure. - Ester-type local anesthetics are metabolized by **plasma pseudocholinesterase**, leading to a shorter duration of action compared to amides. *Benzocaine* - **Benzocaine** is also an ester local anesthetic, but it is typically used topically due to its poor water solubility and absorption. - While an ester, the question implies a common injectable agent, making procaine a more representative answer for the "ester group" in general anesthetic use. *Lignocaine* - **Lignocaine** (also known as lidocaine) is an **amide-type** local anesthetic, which can be identified by an amide linkage in its chemical structure. - Amide local anesthetics are primarily metabolized in the **liver** and generally have a longer duration of action than esters. *Propofol* - **Propofol** is a **short-acting intravenous general anesthetic** and is not classified as a local anesthetic or belonging to the ester group. - It works by potentiation of **GABA-A receptors** and is used for induction and maintenance of general anesthesia.

Q: All are symptoms of morphine withdrawal except?

Fall in BP. ***Fall in BP*** - **Hypotension (fall in BP)** is **not** typically a symptom of opioid withdrawal; rather, **hypertension** can occur due to sympathetic overdrive. - Opioid withdrawal symptoms are primarily characterized by **hyperactivity** and increased sympathetic nervous system activity. *Mydriasis* - **Mydriasis (dilated pupils)** is a classic symptom of opioid withdrawal, resulting from reduced parasympathetic tone and increased sympathetic activity. - In contrast, opioid intoxication causes **miosis (pinpoint pupils)**. *Yawning* - **Yawning** is a very common and early symptom of opioid withdrawal, often accompanied by feelings of fatigue and restlessness. - It reflects generalized **autonomic dysregulation** during withdrawal. *Lacrimation* - **Lacrimation (tearing)** is another prominent autonomic symptom of opioid withdrawal. - This, along with rhinorrhea, contributes to the **"flu-like" symptoms** experienced during withdrawal.

Q: In ophthalmology, if a patient is allergic to aminoesters, which local anesthetic can be safely used?

Prilocaine. **Local anesthetics are classified into two chemical groups: esters (aminoesters) and amides. Allergies to esters typically do not cross-react with amides.** ***Prilocaine*** - **Prilocaine** is an **amide-type local anesthetic**, and allergies to **aminoesters** typically do not cross-react with **amides**. - It is a safe alternative in patients with a known allergy to **ester-type local anesthetics**. *Cocaine* - **Cocaine** is an **ester-type local anesthetic**, sharing a similar chemical structure with **aminoesters**. - Patients allergic to **aminoesters** are likely to experience a **cross-reaction** with **cocaine**. *Procaine* - **Procaine** is a classic **ester-type local anesthetic** (an aminoester). - An allergy to aminoesters directly implies an allergy to **procaine** due to its chemical classification. *Tetracaine* - **Tetracaine** is also an **ester-type local anesthetic** (an aminoester). - It is contraindicated in patients with an allergy to **aminoesters** due to the high risk of **allergic reaction**.

Q: What is the drug of choice for managing generalized tonic-clonic seizures (GTCS) during pregnancy?

Lamotrigine. ***Lamotrigine*** - **Lamotrigine** is considered **one of the preferred drugs** for managing epilepsy during pregnancy due to its relatively **low teratogenic risk** compared to older antiepileptic drugs. - Its established safety profile in pregnancy makes it a preferred option to balance seizure control and **fetal well-being**. - **Important Note:** For **GTCS specifically**, lamotrigine and levetiracetam are both considered appropriate first-line choices, with selection depending on individual patient factors and seizure control history. - Lamotrigine levels **decrease during pregnancy** and require monitoring and dose adjustments. *CBZ* - **Carbamazepine (CBZ)** is associated with an increased risk of **neural tube defects** and other congenital malformations when used during pregnancy, making it less favorable. - While effective for GTCS, its teratogenicity often leads to avoidance or careful consideration of alternatives in pregnant women. *Levetiracetam* - **Levetiracetam** is increasingly recognized as an **excellent choice for GTCS in pregnancy** with a favorable safety profile and growing evidence base. - Many recent guidelines and clinical practices favor levetiracetam as **first-line for GTCS** due to its low risk of major congenital malformations and good efficacy. - It is a **medically appropriate alternative** to lamotrigine, and in some contexts may be preferred, particularly for primary generalized epilepsy. *Valproate* - **Valproate** has the highest risk of **teratogenicity** among common antiepileptic drugs, including a significant risk of **neural tube defects**, developmental delay, autism spectrum disorder, and other anomalies. - Due to these significant risks, valproate is generally **contraindicated** in women of childbearing potential, especially during pregnancy, unless no other effective and safer alternative exists.

Question 1

Which triptan is available in nasal spray form?

Accepted Answer

Sumatriptan

Answer

Rizatriptan

Answer

Naratriptan

Answer

Frovatriptan

Question 2

Where is the benzodiazepine binding site located on GABA receptors?

Accepted Answer

γ-subunit

Answer

β-subunit

Answer

δ-subunit

Answer

α-subunit

Question 3

What is the primary mechanism of action of zonisamide?

Accepted Answer

Sodium channels

Answer

GABA receptors

Answer

Cl- channels

Answer

T-type calcium channels

Question 4

What effect does morphine have on muscle tone?

Accepted Answer

Increased muscle tone

Answer

Respiratory stimulation

Answer

Decreased muscle tone

Answer

Mydriasis

Question 5

What is the classification of Lorcaserin?

Accepted Answer

Anti-obesity

Answer

Anti-anxiety

Answer

Anti-smoking

Answer

Anti-helminthic

Question 6

Which local anaesthetic is known to cause methemoglobinemia?

Accepted Answer

Prilocaine

Answer

Procaine

Answer

Ropivacaine

Answer

Etidocaine

Question 7

Which anaesthetic belongs to the ester group?

Accepted Answer

Procaine

Answer

Lignocaine

Answer

Propofol

Answer

Benzocaine

Question 8

All are symptoms of morphine withdrawal except?

Accepted Answer

Fall in BP

Answer

Yawning

Answer

Lacrimation

Answer

Mydriasis

Question 9

In ophthalmology, if a patient is allergic to aminoesters, which local anesthetic can be safely used?

Accepted Answer

Prilocaine

Answer

Procaine

Answer

Cocaine

Answer

Tetracaine

Question 10

What is the drug of choice for managing generalized tonic-clonic seizures (GTCS) during pregnancy?

Accepted Answer

Lamotrigine

Answer

CBZ

Answer

Levetiracetam

Answer

Valproate

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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