NEET-PG 2015 Pharmacology MCQs — Questions 121–123 (Page 13 of 13)

Q: Modafinil is primarily used for the treatment of which of the following conditions?

Narcolepsy. ***Narcolepsy*** - **Modafinil** is a **eugeroic** (wakefulness-promoting agent) specifically approved and widely used for the treatment of excessive daytime sleepiness associated with **narcolepsy**. - Its mechanism involves increasing **dopamine** and **norepinephrine** levels, and modulating **orexin** pathways, promoting alertness without significant psychomotor stimulation. *Sexual dysfunction* - While sometimes explored off-label for certain types of sexual dysfunction, **modafinil** is not a primary or approved treatment for this condition. - Primary treatments for sexual dysfunction often involve specific medications like **PDE5 inhibitors** or hormone therapy, depending on the cause. *Depression* - **Modafinil** is not a primary antidepressant, although it can be used as an **adjunctive therapy** in some cases to combat residual fatigue or hypersomnia associated with depression. - Standard treatment for depression involves **selective serotonin reuptake inhibitors (SSRIs)**, **serotonin-norepinephrine reuptake inhibitors (SNRIs)**, or other classes of antidepressants. *Anxiety* - **Modafinil** is a stimulant-like drug and can sometimes **exacerbate anxiety** in susceptible individuals due to its catecholaminergic effects. - Primary treatments for anxiety disorders include **selective serotonin reuptake inhibitors (SSRIs)**, **benzodiazepines** (for acute relief), and psychotherapy.

Q: Mechanism of action of thiazides is by -

Inhibiting Na+/Cl- symporter in DCT. **Inhibiting Na+/Cl- symporter in DCT** - Thiazide diuretics primarily act on the **distal convoluted tubule (DCT)** of the nephron [2]. - They inhibit the **Na+/Cl- symporter** (NCC channel) on the apical membrane, preventing reabsorption of sodium and chloride ions [1], [2]. *Inhibiting Na+K+2CI- in descending limb of loop of henle* - The descending limb of the loop of Henle is permeable to water but largely impermeable to solutes; there is no significant Na+K+2Cl- symporter activity here. - This mechanism describes the action of loop diuretics, but they act on the **ascending** limb, not the descending limb. *Inhibiting Na+K+2Cl- in ascending limb of loop of henle* - This mechanism describes the action of **loop diuretics** (e.g., furosemide, bumetanide) [3]. - Loop diuretics inhibit the **Na+K+2Cl- cotransporter (NKCC2)** in the thick ascending limb of the loop of Henle, leading to significant diuresis [3]. *Inhibiting Na+/Cl- symporter in PCT* - The **proximal convoluted tubule (PCT)** is primarily responsible for reabsorbing most of the filtered sodium, chloride, bicarbonate, and other solutes. - While sodium is reabsorbed in the PCT, it's mainly through Na+/H+ exchangers and other mechanisms, not a specific Na+/Cl- symporter that is targeted by thiazides [2].

Q: Which of the following drugs can cause hypertrophic pyloric stenosis?

Erythromycin. ***Erythromycin*** - **Erythromycin** use in infants, particularly during the first few weeks of life, has been associated with an increased risk of developing **hypertrophic pyloric stenosis**. - The mechanism is believed to involve the drug's properties as a **motilin receptor agonist**, which may affect the development or function of the pyloric sphincter. *Nifedipine* - **Nifedipine** is a calcium channel blocker primarily used for cardiovascular conditions like hypertension and angina. - It works by relaxing smooth muscles and is not linked to the development of **pyloric stenosis**. *Vancomycin* - **Vancomycin** is an antibiotic used for severe bacterial infections, particularly against Gram-positive bacteria. - It is not associated with the development of **hypertrophic pyloric stenosis**. *Phenylpropanolamine* - **Phenylpropanolamine** is a sympathomimetic drug previously used as a decongestant and anorectic. - It primarily affects alpha-adrenergic receptors and has no established link to **pyloric stenosis**.

Q121

Modafinil is primarily used for the treatment of which of the following conditions?

Q122

Mechanism of action of thiazides is by -

Q123

Which of the following drugs can cause hypertrophic pyloric stenosis?

NEET-PG 2015 — Pharmacology