What serious side effect may lead to the discontinuation of felbamate?
Which of the following is a mineralocorticoid antagonist?
Lithium directly affects which ion ?
Which anxiolytic acts through 5-HT1A receptor partial agonism without exhibiting significant anticonvulsant or muscle relaxant properties?
What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?
Thiazides act on which part of the nephron?
Which of the following is NOT typically produced by local anesthetics?
Which of the following is a tricyclic antidepressant?
Which of the following antidiabetic drugs (other than insulin) is indicated as adjunct therapy for the management of both type I and type II diabetes mellitus?
What is the best drug for control of acute esophageal variceal bleeding?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 61: What serious side effect may lead to the discontinuation of felbamate?
- A. Seizures
- B. Renal impairment
- C. Gastrointestinal disorder
- D. Aplastic anemia (Correct Answer)
Explanation: ***Aplastic anemia*** - Felbamate is known to cause **aplastic anemia**, a severe and life-threatening condition where the **bone marrow stops producing enough new blood cells**. - Felbamate carries a **black box warning** for both aplastic anemia and **hepatotoxicity (severe liver failure)**, which are the two most serious adverse effects leading to discontinuation. - Due to this significant risk, felbamate is reserved for severe, refractory epilepsy cases, and patients require **regular monitoring** of blood counts and liver function tests. *Renal impairment* - While some medications can cause renal impairment, **felbamate is not primarily associated** with this side effect to the extent of requiring discontinuation. - Its metabolism and excretion are predominantly **hepatic (liver)**, and renal effects are less common or severe. *Gastrointestinal disorder* - Gastrointestinal side effects like nausea or vomiting are **common with many medications**, including felbamate, but are generally **mild and manageable**, rarely leading to discontinuation. - These effects are usually **dose-dependent** and can often be mitigated with supportive care. *Seizures* - Felbamate is an **antiepileptic drug (AED)**, so it is used to treat seizures, not cause them. - If a patient experiences seizures while on felbamate, it usually indicates **inadequate treatment response** or seizure exacerbation, rather than a direct side effect necessitating discontinuation for toxicity.
Question 62: 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 63: 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 64: 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 65: 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 66: 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 67: Which of the following is NOT typically produced by local anesthetics?
- A. Muscle relaxation
- B. Euphoria
- C. Dysphoria (Correct Answer)
- D. Analgesia
Explanation: Detailed Analysis: ***Dysphoria*** - While local anesthetics can cause a range of central nervous system effects with toxicity, **dysphoria** (a state of unease or generalized dissatisfaction with life) is not a typical or primary direct effect of their action on receptors. High doses or systemic absorption might lead to anxiety and restlessness, but dysphoria specifically is uncommon. - The primary mechanism of local anesthetics involves blocking **voltage-gated sodium channels** [1], leading to a reversible loss of sensation, not directly causing mood disturbances like dysphoria. *Euphoria* - **Euphoria** can sometimes be observed with systemic local anesthetic toxicity due to initial CNS stimulation before depression. Some individuals report a transient feeling of well-being or altered mental status with high systemic levels of certain local anesthetics. - This effect is not a direct therapeutic goal but rather an **adverse reaction** associated with systemic absorption and CNS excitation. *Analgesia* - **Analgesia** is the primary therapeutic effect of local anesthetics, achieved by blocking nerve impulse transmission. This prevents the sensation of pain from reaching the brain [1]. - They work by **blocking sodium channels** in nerve membranes [1], thereby inhibiting the initiation and propagation of action potentials [2]. *Muscle relaxation* - **Muscle relaxation** in the area of blockade is a direct consequence of the local anesthetic's action on the motor nerves supplying the muscles. - By blocking nerve conduction in **motor nerve fibers** [1], local anesthetics prevent muscle contraction, leading to temporary skeletal muscle paralysis.
Question 68: 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 69: Which of the following antidiabetic drugs (other than insulin) is indicated as adjunct therapy for the management of both type I and type II diabetes mellitus?
- A. Sulphonylureas
- B. Metformin
- C. Acarbose
- D. Pramlintide (Correct Answer)
Explanation: Pramlintide - Pramlintide is an amylin analog indicated as an adjunct therapy to insulin for both type 1 and type 2 diabetes, helping to regulate post-prandial glucose. - It slows gastric emptying, suppresses postprandial glucagon secretion, and promotes satiety, leading to reduced insulin requirements and improved glycemic control. Sulphonylureas - Sulphonylureas primarily stimulate insulin secretion from pancreatic beta cells, making them effective only in Type 2 diabetes where some beta-cell function is preserved [2]. - They are not indicated for Type 1 diabetes because these patients have absolute insulin deficiency due to beta cell destruction. Metformin - Metformin is a biguanide that primarily reduces hepatic glucose production and improves insulin sensitivity in peripheral tissues. - It is a first-line treatment for Type 2 diabetes but is generally not used for Type 1 diabetes as it does not address the fundamental lack of insulin. Acarbose - Acarbose is an alpha-glucosidase inhibitor that works by delaying carbohydrate absorption from the gastrointestinal tract, thus reducing postprandial glucose spikes [1]. - While it can be used in Type 2 diabetes to manage postprandial hyperglycemia, it is not typically indicated as an adjunct for Type 1 diabetes alongside insulin [3].
Question 70: What is the best drug for control of acute esophageal variceal bleeding?
- A. Vasopressin
- B. GnRH
- C. Octreotide (Correct Answer)
- D. Propranolol
Explanation: ***Octreotide*** - **Octreotide** is a somatostatin analog that causes **splanchnic vasoconstriction**, reducing portal venous inflow and pressure, which is crucial in controlling **esophageal variceal bleeding**. - Its mechanism involves inhibiting the release of **vasodilatory hormones** like glucagon, leading to a decrease in portal pressure without significant systemic side effects. *Vasopressin* - **Vasopressin** is a potent vasoconstrictor that can reduce portal pressure but has significant systemic side effects such as **myocardial ischemia** and **bowel ischemia** due to widespread vasoconstriction. - It is generally no longer considered the first-line pharmacological treatment for variceal bleeding due to its **adverse effect profile**. *GnRH* - **GnRH** (Gonadotropin-releasing hormone) plays a role in regulating the reproductive system by controlling the release of FSH and LH from the pituitary. - It has **no direct role** in the management or control of esophageal bleeding. *Propranolol* - **Propranolol** is a non-selective beta-blocker primarily used for **prophylaxis** of variceal bleeding by reducing portal pressure chronically. - It works by reducing cardiac output and causing splanchnic vasoconstriction, but it is **not used for acute control** of active bleeding.