NEET-PG 2018 - Pharmacology PYQs Practice Questions

Q: What is the physiological dose of hydrocortisone (mg/m2/day)?

10-12 mg/m²/day. ***10-12 mg/m²/day*** - This range represents the typical **physiological replacement dose** of hydrocortisone, mimicking the body's natural cortisol production. - This dose is used for patients with **adrenal insufficiency** to maintain normal metabolic functions without causing significant side effects. *8-10 mg/m²/day* - This dose is slightly on the lower side of the accepted physiological range and might not be sufficient for complete replacement in all individuals. - While close, it is not the most commonly cited optimal physiological dose for hydrocortisone replacement. *15-18 mg/m²/day* - This dose is typically considered above the physiological replacement level and may begin to cause **mild corticosteroid side effects** with prolonged use. - It might be used for short periods or in specific conditions, but not as a standard physiological replacement. *20-25 mg/m²/day* - This dose is well above the physiological range and would be considered a **pharmacological dose** often used for its anti-inflammatory or immunosuppressive effects. - Prolonged use at this dose would likely lead to significant **corticosteroid side effects** such as Cushingoid features, osteoporosis, and hyperglycemia. [Practice more Pharmacology PYQs on OnCourse]

Q: Which drug requires continuous monitoring of prothrombin time?

Coumadin. ***Coumadin*** - **Coumadin (warfarin)** is an oral anticoagulant that inhibits vitamin K epoxide reductase, thereby reducing the synthesis of **vitamin K-dependent clotting factors** (II, VII, IX, X). - Its narrow therapeutic index and significant variability in dosage requirements necessitate continuous monitoring of the **prothrombin time (PT)**, reported as the **International Normalized Ratio (INR)**, to ensure efficacy and prevent bleeding complications. *Aspirin* - **Aspirin** is an antiplatelet agent that irreversibly inhibits cyclooxygenase-1 (COX-1), preventing the synthesis of thromboxane A2, which is crucial for platelet aggregation. - It does not directly affect the coagulation cascade or prothrombin time; its antiplatelet effects are typically monitored by patient response and bleeding time, though routine monitoring is not usually required for standard antiplatelet therapy. *Digoxin* - **Digoxin** is a cardiac glycoside used to treat heart failure and atrial fibrillation by increasing myocardial contractility and slowing AV nodal conduction. - Its therapeutic effects and potential toxicity are monitored through serum digoxin levels, electrolyte balance (especially potassium), and electrocardiograms for signs of dysrhythmias, not by prothrombin time. *Lepirudin* - **Lepirudin** is a direct thrombin inhibitor (DTI) used in patients with heparin-induced thrombocytopenia (HIT). - Its anticoagulant effect is typically monitored using the **activated partial thromboplastin time (aPTT)**, not prothrombin time. [Practice more Pharmacology PYQs on OnCourse]

Q: Mycoplasma is inherently resistant to which of the following antibiotic classes due to its lack of a peptidoglycan cell wall?

Ceftriaxone (a cephalosporin). ***Ceftriaxone (a cephalosporin)*** - Cephalosporins are **beta-lactam antibiotics** that inhibit **peptidoglycan cell wall synthesis** by binding to penicillin-binding proteins (PBPs) - *Mycoplasma* species **completely lack a peptidoglycan cell wall**, which is the primary target of all beta-lactam antibiotics - Therefore, cephalosporins (and all beta-lactams) are **inherently ineffective** against *Mycoplasma* infections - This is a classic example of **intrinsic resistance** due to absence of the drug target *Penicillins (e.g., Amoxicillin)* - While penicillins are also beta-lactam antibiotics that target cell wall synthesis, the question specifically asks about ceftriaxone - Penicillins are similarly ineffective against *Mycoplasma* for the same reason (lack of cell wall) - However, when given a specific drug example (ceftriaxone), it is the most precise answer *Aminoglycosides (e.g., Gentamicin)* - Aminoglycosides target the **30S ribosomal subunit** to inhibit **protein synthesis** - While they have **poor penetration** into *Mycoplasma* cells and limited clinical efficacy, the resistance is not due to lack of cell wall - The mechanism of reduced susceptibility is different from the intrinsic resistance seen with beta-lactams *Fluoroquinolones (e.g., Ciprofloxacin)* - Fluoroquinolones inhibit **DNA gyrase** and **topoisomerase IV**, enzymes essential for DNA replication - These antibiotics are **effective** against *Mycoplasma* species and are commonly used to treat *Mycoplasma* infections - They represent appropriate treatment options along with macrolides and tetracyclines [Practice more Pharmacology PYQs on OnCourse]

Q: At pKa = pH, what is the relationship between the ionic and non-ionic forms of a drug?

Conc. of drug is 50% ionic and 50% non-ionic. ***Conc. of drug is 50% ionic and 50% non-ionic*** - At **pKa = pH**, the concentrations of the **ionized** and **unionized** forms of a drug are equal as per the **Henderson-Hasselbalch equation**. - This means that exactly **half** of the drug molecules are in their charged (ionic) state, and the other half are in their uncharged (non-ionic) state. *Absorption of drug is 50% ionic and 50% non-ionic* - The amount of drug that is absorbed is dependent on the **non-ionic concentration** available at the absorption site, but this option incorrectly states that the *absorption itself* is 50% ionic. - Absorption primarily occurs for the **non-ionic, lipophilic form** as it can more readily cross cell membranes. *Conc. of drug is 75% ionic and 25% non-ionic* - This ratio would occur when the **pH** is either 0.5 units above the pKa for a weak acid or 0.5 units below the pKa for a weak base. - For example, if **pH = pKa + 0.5** (for a weak acid), approximately 75% would be ionic. *Conc. of drug is 25% ionic and 75% non-ionic* - This ratio would occur when the **pH** is either 0.5 units below the pKa for a weak acid or 0.5 units above the pKa for a weak base. - For example, if **pH = pKa - 0.5** (for a weak acid), approximately 25% would be ionic. [Practice more Pharmacology PYQs on OnCourse]

Question 1

What is the mechanism of action of Curare drugs as muscle relaxants?

Accepted Answer

Act competitively on Ach receptors blocking post-synaptically

Answer

Persistently depolarizing at Neuromuscular junction

Answer

Repetitive stimulation of Ach receptors on muscle end plate

Answer

Inhibiting the calcium channel on presynaptic membrane

Question 2

What is the physiological dose of hydrocortisone (mg/m2/day)?

Accepted Answer

10-12 mg/m²/day

Answer

20-25 mg/m²/day

Answer

15-18 mg/m²/day

Answer

8-10 mg/m²/day

Question 3

Which drug requires continuous monitoring of prothrombin time?

Accepted Answer

Coumadin

Answer

Digoxin

Answer

Aspirin

Answer

Lepirudin

Question 4

Mycoplasma is inherently resistant to which of the following antibiotic classes due to its lack of a peptidoglycan cell wall?

Accepted Answer

Ceftriaxone (a cephalosporin)

Answer

Penicillins (e.g., Amoxicillin)

Answer

Aminoglycosides (e.g., Gentamicin)

Answer

Fluoroquinolones (e.g., Ciprofloxacin)

Question 5

At pKa = pH, what is the relationship between the ionic and non-ionic forms of a drug?

Accepted Answer

Conc. of drug is 50% ionic and 50% non-ionic

Answer

Absorption of drug is 50% ionic and 50% non-ionic

Answer

Conc. of drug is 25% ionic and 75% non-ionic

Answer

Conc. of drug is 75% ionic and 25% non-ionic

Question 6

Endothelin primarily acts through which type of receptors?

Accepted Answer

Endothelin receptor type A (ETA)

Answer

Calcium receptors

Answer

General receptor type (GPCRs)

Answer

Endothelin receptor type B (ETB)

Question 7

Which drug is primarily used to promote fetal lung maturity?

Accepted Answer

Dexamethasone

Answer

Folic acid

Answer

Beclomethasone

Question 8

Which drug decreases the bone resorption in osteoporosis?

Accepted Answer

Risedronate

Answer

Teriparatide

Answer

Cortisone

Answer

Cimetidine

Question 9

What is mechanism of action of colchicine in acute gout?

Accepted Answer

Inhibition of leukocyte migration and microtubule function

Answer

Inhibition of purine metabolism

Answer

Inhibition of uric acid conversion

Answer

Migration of leukocytes

Question 10

Burkholderia cepacia is resistant to which of the following antibiotics?

Accepted Answer

Cefotetan

Answer

Trimethoprim-sulfamethoxazole

Answer

Ceftazidime

Answer

Temocillin

NEET-PG 2018 — Pharmacology