What is the mechanism of action of Abatacept?
Why do NSAIDs cause gastric ulcers?
Which of the following is a mineralocorticoid antagonist?
Thiazides act on which part of the nephron?
What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?
Which anxiolytic acts through 5-HT1A receptor partial agonism without exhibiting significant anticonvulsant or muscle relaxant properties?
Lithium directly affects which ion ?
Which of the following is a classic tricyclic antidepressant (TCA) commonly used as the prototype for the class?
Which of the following is a tricyclic antidepressant?
Visual field monitoring is important before starting which of the following drugs for epilepsy treatment?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 71: What is the mechanism of action of Abatacept?
- A. Tumor necrosis factor (TNF) alpha inhibitor
- B. Monoclonal antibody against interleukin-6 (IL-6) receptor
- C. Interleukin-1 (IL-1) receptor antagonist
- D. Inhibitor of co-stimulation of T cells (Correct Answer)
Explanation: ***Inhibitor of co-stimulation of T cells*** - Abatacept is a **fusion protein** that blocks the **CD28-CD80/86 co-stimulatory pathway**, which is crucial for full T-cell activation. - By binding to **CD80** and **CD86** on antigen-presenting cells, it prevents their interaction with **CD28** on T cells, thus inhibiting T-cell proliferation and cytokine production. *Tumor necrosis factor (TNF) alpha inhibitor* - TNF alpha inhibitors (e.g., **adalimumab**, **infliximab**, **etanercept**) bind to and neutralize **TNF alpha**, a pro-inflammatory cytokine. - While used in similar conditions, their mechanism is distinct from Abatacept's T-cell co-stimulation blockade. *Monoclonal antibody against interleukin-6 (IL-6) receptor* - Drugs like **tocilizumab** target the **IL-6 receptor**, blocking the signaling of **IL-6**, another important inflammatory cytokine. - This mechanism primarily affects cytokine signaling rather than directly inhibiting T-cell activation in the same way as abatacept. *Interleukin-1 (IL-1) receptor antagonist* - **Anakinra** is an example of an **IL-1 receptor antagonist**, which competes with IL-1 for binding to its receptor, thereby blocking its pro-inflammatory effects. - This mechanism focuses on inhibiting the action of IL-1, unlike Abatacept's role in T-cell activation.
Question 72: Why do NSAIDs cause gastric ulcers?
- A. They increase gastric acid secretion
- B. They delay gastric emptying
- C. They inhibit the production of protective mucus
- D. They inhibit COX-1 and COX-2 enzymes (Correct Answer)
Explanation: ***They inhibit COX-1 and COX-2 enzymes*** - NSAIDs primarily exert their anti-inflammatory effects by inhibiting **cyclooxygenase (COX) enzymes**, specifically COX-1 and COX-2. - While COX-2 inhibition is responsible for anti-inflammatory action, **COX-1 inhibition** reduces the production of protective prostaglandins in the gastric mucosa, leading to a loss of mucosal integrity and an increased risk of ulceration. *They inhibit the production of protective mucus* - While NSAIDs do compromise the gastric mucosal barrier, their primary mechanism is not a direct inhibition of mucus production itself. - Instead, the reduced prostaglandin synthesis indirectly affects the quantity and quality of mucus and bicarbonate, which are crucial for mucosal defense. *They increase gastric acid secretion* - NSAIDs do not directly increase gastric acid secretion; in fact, some studies suggest a mild inhibitory effect. - The main problem is the diminished mucosal protection against the normal levels of gastric acid. *They delay gastric emptying* - Delaying gastric emptying is not a primary mechanism by which NSAIDs cause ulcers. - While some medications can affect gastric motility, this is not the key pathway for NSAID-induced gastropathy.
Question 73: Which of the following is a mineralocorticoid antagonist?
- A. Spironolactone (Correct Answer)
- B. Inamrinone
- C. Nicorandil
- D. Ketorolac
Explanation: ***Spironolactone*** - **Spironolactone** is a **potassium-sparing diuretic** that acts as a competitive antagonist of **aldosterone** at the mineralocorticoid receptors in the renal tubules [1], [2]. - Its primary use is in conditions like **heart failure**, **cirrhosis with ascites**, and **primary hyperaldosteronism** (Conn's syndrome) [2]. *Inamrinone* - **Inamrinone** is a **phosphodiesterase-3 inhibitor** (PDE3 inhibitor) and is classified as an **inotropic agent**. - It increases **intracellular cAMP** in cardiac cells, leading to increased **contractility** and **vasodilation**, and is used in severe heart failure. *Nicorandil* - **Nicorandil** is a **potassium channel opener** and a **nitrate-like drug** that causes both venous and arterial vasodilation. - It is primarily used as an **antianginal agent** due to its ability to reduce cardiac workload and improve coronary blood flow. *Ketorolac* - **Ketorolac** is a **nonsteroidal anti-inflammatory drug (NSAID)** that primarily inhibits **cyclooxygenase (COX) enzymes**. - It is used for **short-term management of acute moderate to severe pain** and has no direct activity on mineralocorticoid receptors.
Question 74: Thiazides act on which part of the nephron?
- A. Proximal Convoluted Tubule
- B. Descending limb of loop of Henle
- C. Glomerulus
- D. Distal Convoluted Tubule (Correct Answer)
Explanation: ***Distal Convoluted Tubule*** - **Thiazide diuretics** specifically inhibit the **sodium-chloride cotransporter (NCC)** in the apical membrane of cells in the distal convoluted tubule. - This inhibition leads to decreased reabsorption of sodium and chloride, resulting in increased excretion of water, sodium, and chloride. *Proximal Convoluted Tubule* - The proximal convoluted tubule is the primary site for reabsorption of the majority of filtered substances, including sodium, bicarbonate, glucose, and amino acids. - While some diuretics like **acetazolamide** (a carbonic anhydrase inhibitor) act here, thiazides do not. *Glomerulus* - The **glomerulus** is primarily responsible for the **filtration** of blood, forming the initial filtrate. - It is not a site for diuretic action as it does not participate in active reabsorption or secretion of electrolytes. *Descending limb of loop of Henle* - The descending limb is highly permeable to **water** but impermeable to solutes, leading to water reabsorption due to the hyperosmotic medulla. - Diuretics typically do not act on this segment to inhibit solute transport, though osmotic diuretics can affect water movement here.
Question 75: What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?
- A. Norepinephrine reuptake inhibition only
- B. Anticholinergic effects on the heart
- C. Both norepinephrine reuptake inhibition and anticholinergic effects on the heart (Correct Answer)
- D. Direct membrane stabilizing effects only
Explanation: ***Both norepinephrine reuptake inhibition and anticholinergic effects on the heart*** - **Tricyclic antidepressants (TCAs)** block the reuptake of **norepinephrine**, which can lead to increased sympathetic tone on the heart and potentially **tachyarrhythmias** or other cardiac complications. - TCAs also have potent **anticholinergic effects**, blocking muscarinic receptors in the heart; this can increase **heart rate** and affect cardiovascular stability. - While **direct membrane stabilizing effects** (sodium channel blockade) are critical for **QRS widening and conduction delays**, the combination of norepinephrine reuptake inhibition and anticholinergic effects accounts for the broader spectrum of **TCA-induced cardiac toxicity** including tachycardia and hemodynamic instability. *Norepinephrine reuptake inhibition only* - While TCAs do inhibit norepinephrine reuptake contributing to tachycardia and increased sympathetic tone, this mechanism alone does not fully explain the breadth of cardiac effects seen with these drugs. - The **anticholinergic effects** play a significant additional role in altering cardiac function. *Anticholinergic effects on the heart* - While TCAs do exert anticholinergic effects that can impact heart rate and cardiovascular function, this mechanism alone fails to account for the additional contributions from **norepinephrine reuptake inhibition** to the overall cardiac toxicity. - The combination of both mechanisms is necessary for a complete understanding of **TCA-induced cardiac effects**. *Direct membrane stabilizing effects only* - This option refers to the **quinidine-like action** of TCAs, which involves blocking myocardial fast sodium channels, leading to a **prolonged QRS interval** and increased risk of **ventricular arrhythmias** and **conduction defects**. - While direct membrane stabilization is the **primary mechanism of TCA-induced conduction abnormalities** (QRS widening, heart blocks), the question asks for mechanisms of broader **cardiac toxicity**, which includes the combined effects of norepinephrine reuptake inhibition and anticholinergic actions on heart rate and hemodynamics.
Question 76: Which anxiolytic acts through 5-HT1A receptor partial agonism without exhibiting significant anticonvulsant or muscle relaxant properties?
- A. Diazepam
- B. Zolpidem
- C. Phenobarbitone
- D. Buspirone (Correct Answer)
Explanation: ***Buspirone*** - **Buspirone** is a unique anxiolytic that primarily acts as a **partial agonist at 5-HT1A receptors**. - Unlike benzodiazepines, it lacks significant **anticonvulsant**, **muscle relaxant**, or **sedative-hypnotic properties** and does not lead to physical dependence or withdrawal. *Diazepam* - **Diazepam** is a **benzodiazepine** that acts by enhancing the effect of **GABA** at GABA-A receptors, leading to significant anxiolytic, sedative, muscle relaxant, and anticonvulsant effects. - It does not primarily act via **5-HT1A receptor partial agonism**. *Zolpidem* - **Zolpidem** is a **non-benzodiazepine hypnotic** that selectively binds to the **GABA-A receptor** subunit, primarily mediating sedative effects. - While it's used for insomnia, it doesn't primarily act as a **5-HT1A partial agonist** and is not typically used for its anxiolytic properties in the same way as buspirone. *Phenobarbitone* - **Phenobarbitone** is a **barbiturate** that acts by prolonging the opening of **chloride channels** associated with GABA-A receptors, leading to strong sedative, hypnotic, and anticonvulsant effects. - Its mechanism of action is distinct from **5-HT1A receptor partial agonism**, and it carries a high risk of dependence and overdose.
Question 77: Lithium directly affects which ion ?
- A. Sodium (Correct Answer)
- B. Potassium
- C. Magnesium
- D. Calcium
Explanation: ***Sodium*** - Lithium directly interferes with **sodium ion transport** across cell membranes, particularly by inhibiting the **Na+/K+-ATPase** pump. - This interference alters intracellular sodium concentrations and affects neural excitability, contributing to its **mood-stabilizing** effects. *Potassium* - While potassium transport is linked to the **Na+/K+-ATPase pump**, lithium primarily acts through its effect on **sodium transport**, rather than directly mimicking or significantly altering potassium. - Changes in potassium levels due to lithium are largely secondary to its primary impact on sodium. *Magnesium* - Lithium has a more direct impact on **sodium channels** and transporters, contrasting with its less direct or significant interaction with magnesium metabolism. - Though magnesium is crucial for numerous cellular processes, it is not the primary ion directly affected by lithium's therapeutic actions. *Calcium* - Lithium does not directly affect **calcium channels** or calcium signaling pathways in the same way it impacts sodium. - While lithium may indirectly influence calcium-dependent processes, its primary direct target for therapeutic effects is not calcium.
Question 78: Which of the following is a classic tricyclic antidepressant (TCA) commonly used as the prototype for the class?
- A. Amitriptyline (Correct Answer)
- B. Citalopram
- C. Venlafaxine
- D. Nortriptyline
Explanation: ***Amitriptyline*** - **Amitriptyline** is a classic tricyclic antidepressant (TCA) and is widely recognized for its use in treating depression, neuropathic pain, and migraine prophylaxis. Its characteristic side effect profile, including **anticholinergic effects** and **sedation**, is well-known. - It is one of the **oldest and most frequently prescribed TCAs**, making it a common reference point in pharmacology and clinical practice. *Citalopram* - **Citalopram** is an **SSRI** (selective serotonin reuptake inhibitor), not a TCA. It works by selectively inhibiting the reuptake of serotonin. - It has a different side effect profile compared to TCAs, generally with fewer anticholinergic and cardiovascular effects. *Venlafaxine* - **Venlafaxine** is an **SNRI** (serotonin-norepinephrine reuptake inhibitor), not a TCA. It inhibits the reuptake of both serotonin and norepinephrine. - It has efficacy in treating depression and anxiety disorders, but its mechanism of action is distinct from TCAs. *Nortriptyline* - **Nortriptyline** is indeed a TCA, specifically a **secondary amine TCA**, which is an active metabolite of amitriptyline. - While it is a TCA, amitriptyline is generally more broadly recognized and used as the prototype for the class, with nortriptyline often being highlighted for its slightly better tolerability profile (e.g., less sedation, less orthostatic hypotension) compared to tertiary amine TCAs like amitriptyline.
Question 79: Which of the following is a tricyclic antidepressant?
- A. Fluoxetine
- B. Citalopram
- C. Doxepin (Correct Answer)
- D. Venlafaxine
Explanation: ***Doxepin*** - **Doxepin** is a **tricyclic antidepressant (TCA)** that inhibits the reuptake of **serotonin** and **norepinephrine**, and also has significant **histaminergic** and **cholinergic** blocking effects. - TCAs, including doxepin, are commonly used for treating **depression**, **anxiety**, and certain pain conditions. *Venlafaxine* - **Venlafaxine** is a **serotonin-norepinephrine reuptake inhibitor (SNRI)**, not a tricyclic antidepressant. - SNRIs selectively block the reuptake of both **serotonin** and **norepinephrine**, but lack the broad receptor affinity of TCAs. *Fluoxetine* - **Fluoxetine** is a **selective serotonin reuptake inhibitor (SSRI)**, which specifically targets serotonin reuptake. - SSRIs are generally considered a first-line treatment for depression due to a more favorable side effect profile compared to TCAs. *Citalopram* - **Citalopram** is also a **selective serotonin reuptake inhibitor (SSRI)**, much like fluoxetine. - It works by increasing the levels of **serotonin** in the brain by blocking its reuptake, differentiating it from tricyclic antidepressants.
Question 80: Visual field monitoring is important before starting which of the following drugs for epilepsy treatment?
- A. Vigabatrin (Correct Answer)
- B. Topiramate
- C. Valproic acid
- D. Carbamazepine
Explanation: ***Vigabatrin*** - **Vigabatrin** is known to cause **irreversible concentric visual field constriction** (peripheral vision loss) due to retinal toxicity. - Regular **ophthalmological monitoring**, including **visual field testing**, is crucial before and during treatment to detect and manage this adverse effect early. *Topiramate* - Topiramate can cause **acute angle-closure glaucoma** and **myopia**, which affect vision, but regular visual field monitoring is not a primary requirement for this specific side effect. - Its main concerns often relate to cognitive side effects and kidney stones, rather than progressive visual field loss requiring baseline and ongoing field testing. *Valproic acid* - Valproic acid is not typically associated with specific visual field defects requiring routine monitoring. - Its major side effects often involve **hepatotoxicity**, **pancreatitis**, and **teratogenicity**. *Carbamazepine* - Carbamazepine's notable side effects include **aplastic anemia**, **hyponatremia**, and **Stevens-Johnson syndrome**. - While it can cause some ocular side effects like **diplopia** or **nystagmus**, it does not typically lead to the progressive and irreversible visual field constriction seen with vigabatrin, which necessitates strict monitoring.