NEET-PG 2012 - Pharmacology Practice Questions

Q: Which enzyme is irreversibly inhibited by aspirin?

Cyclooxygenase. ***Cyclooxygenase*** - **Aspirin** irreversibly inhibits **cyclooxygenase (COX-1 and COX-2)** by acetylating a serine residue in the enzyme's active site. - This irreversible inhibition prevents the production of **prostaglandins, thromboxane**, and **prostacyclin**, thereby reducing inflammation, pain, fever, and platelet aggregation. *Lipooxygenase* - **Lipooxygenase** is involved in the synthesis of **leukotrienes**, which are mediators of inflammation and allergic responses. - Aspirin does not directly inhibit lipooxygenase; rather, it primarily targets the COX pathway. *Thromboxane synthase* - **Thromboxane synthase** is an enzyme downstream of COX, responsible for converting prostaglandin H2 into **thromboxane A2**. - While aspirin's effect on platelet aggregation is due to reduced thromboxane A2 synthesis via COX inhibition, it does not directly inhibit thromboxane synthase itself. *Phospholipase* - **Phospholipase A2** is responsible for releasing **arachidonic acid** from cell membrane phospholipids, which is the initial step in both the cyclooxygenase and lipooxygenase pathways. - Aspirin does not directly inhibit phospholipase A2; its action occurs later in the cascade.

Q: Side effects of thiazide diuretics include all of the following except?

Hypocalcemia. ***Hypocalcemia*** - Thiazide diuretics are known to cause **hypercalcemia** (increased calcium reabsorption), NOT hypocalcemia, due to their action on the distal convoluted tubule. - This property makes them useful in treating conditions like **idiopathic hypercalciuria** and **calcium-containing kidney stones**. - The mechanism involves enhanced passive calcium reabsorption in the proximal tubule and active reabsorption in the distal tubule. *Hyponatremia* - Thiazide diuretics impair the kidney's ability to dilute urine and reabsorb sodium in the distal tubule, leading to **increased sodium excretion** and potential hyponatremia. - This effect is more pronounced in **elderly patients** and those with increased free water intake. - Hyponatremia is one of the most common electrolyte disturbances with thiazides. *Hypokalemia* - Thiazides increase the delivery of sodium and water to the collecting duct, leading to increased activity of the **renin-angiotensin-aldosterone system** and enhanced potassium secretion. - This results in **potassium wasting** and hypokalemia, which may require potassium supplementation or combination with potassium-sparing diuretics. *Erectile dysfunction* - Thiazide diuretics can cause **erectile dysfunction** through mechanisms including effects on vascular smooth muscle, reduced blood flow, and possible hormonal effects. - This is a common side effect reported in male patients using these medications for hypertension and may affect compliance.

Q: Which of the following is an intermediate-acting insulin?

NPH insulin. ***NPH insulin*** - **NPH (Neutral Protamine Hagedorn) insulin** is characterized by its intermediate duration of action, typically peaking in 4-12 hours and lasting up to 24 hours [1]. - This intermediate profile is achieved by combining insulin with **protamine**, which slows its absorption from the subcutaneous injection site [1]. *Insulin lispro* - **Insulin lispro** is a **rapid-acting insulin** analog, designed to act very quickly after injection, typically within 15-30 minutes [1, 2]. - Its quick onset and short duration make it suitable for dosing **immediately before meals** to control post-prandial glucose levels [1]. *Regular insulin* - **Regular insulin** is a **short-acting insulin**, with an onset of action around 30-60 minutes and a peak effect typically within 2-4 hours. - It is often administered **30 minutes before meals** and can also be used intravenously in acute situations like diabetic ketoacidosis. *Insulin glargine* - **Insulin glargine** is a **long-acting insulin** analog, providing a prolonged and relatively peakless effect over 24 hours [1, 2]. - Its primary role is to provide **basal insulin coverage**, mimicking the body's continuous background insulin production [1, 2].

Q: Long-term steroid ingestion leads to all of the following except:

Hypoglycemia. ***Hypoglycemia*** - Chronic steroid use primarily leads to **hyperglycemia** due to increased **gluconeogenesis** and **insulin resistance**, not hypoglycemia. - Steroids raise blood glucose levels, potentially inducing or worsening **diabetes mellitus**. *Avascular necrosis of head of femur* - Long-term steroid use is a well-established risk factor for **avascular necrosis**, particularly affecting the **femoral head**. - This occurs due to impaired blood supply to the bone, leading to its death. *Cataract* - **Posterior subcapsular cataracts** are a known ocular complication of prolonged systemic corticosteroid therapy. - The mechanism involves direct effects of steroids on lens metabolism and protein aggregation. *Growth retardation* - In children, chronic corticosteroid therapy can suppress growth, leading to **growth retardation**. - This is due to interference with **growth hormone secretion** and direct effects on bone formation.

Q: Which antilipidemic drug reduces cholesterol levels by inhibiting cholesterol absorption?

Ezetimibe. ***Ezetimibe*** - **Ezetimibe** selectively inhibits the **Niemann-Pick C1-Like 1 (NPC1L1) protein**, which is responsible for plant sterol and cholesterol absorption in the small intestine. - This action leads to a reduction in **LDL-C** levels by decreasing the amount of cholesterol available to the liver. *Orlistat* - **Orlistat** is a **lipase inhibitor** that prevents the absorption of dietary fats by inhibiting gastric and pancreatic lipases. - While it aids in weight loss and can indirectly improve lipid profiles, its primary mechanism is *not* direct inhibition of cholesterol absorption. *Cholestyramine* - **Cholestyramine** is a **bile acid sequestrant** that binds to bile acids in the intestine, preventing their reabsorption. - This increases the excretion of bile acids, prompting the liver to synthesize more bile acids from cholesterol, thereby lowering cholesterol levels, but it does *not* directly inhibit cholesterol absorption. *Statins* - **Statins** (HMG-CoA reductase inhibitors) are considered first-line agents for lowering cholesterol by inhibiting the **rate-limiting step in cholesterol synthesis** in the liver. - Their primary action is to reduce endogenous cholesterol production, not to block cholesterol absorption from the gut.

Q: Which sulphonamide has the longest acting duration?

Sulphadoxine. ***Sulphadoxine*** - **Sulphadoxine** is known for its **exceptionally long elimination half-life**, which is due to its high plasma protein binding and slow renal excretion. - This property allows for **once-weekly dosing**, making it one of the longest-acting sulfonamides, often used in combinations for malaria prophylaxis or treatment. *Sulfadiazine* - **Sulfadiazine** has an intermediate half-life, typically requiring **multiple daily doses**. - It is commonly used for infections like **toxoplasmosis** and **nocardiosis**. *Sulfamethoxazole* - **Sulfamethoxazole** has an intermediate half-life, usually requiring **twice-daily administration**. - It is most famously co-formulated with **trimethoprim** (as co-trimoxazole) for a broad range of bacterial infections. *Sulfamethiazole* - **Sulfamethiazole** is a **short-acting sulfanilamide derivative** with a rapid elimination, meaning it would require frequent dosing. - It is not commonly used systemically due to its short duration of action.

Q: All are true about ciprofloxacin except?

More active at acidic pH. ***More active at acidic pH*** - Fluoroquinolones, including ciprofloxacin, exhibit **reduced antibacterial activity in acidic environments**. Their efficacy is generally better at **neutral or alkaline pH**. - This is clinically relevant as fluoroquinolones may have **reduced effectiveness in acidic sites** like the stomach or acidic urine. - The optimal antibacterial activity occurs at physiological or slightly alkaline pH. *DNA gyrase inhibition* - Ciprofloxacin, like other fluoroquinolones, exerts its antibacterial effect by inhibiting **bacterial DNA gyrase (topoisomerase II)** and **topoisomerase IV**. - This inhibition prevents DNA replication and repair, leading to bacterial cell death. *Contraindicated in pregnancy* - Ciprofloxacin is generally **contraindicated in pregnancy** due to concerns about potential harm to the developing fetus, particularly effects on **cartilage development**. - However, it may be used in specific, life-threatening situations if the benefit outweighs the potential risk. *Second generation fluoroquinolone* - Ciprofloxacin is classified as a **second-generation fluoroquinolone**. - This class includes agents with improved activity against Gram-negative bacteria and some atypical organisms.

Q: Which steroid has the maximum mineralocorticoid activity?

Fludrocortisone. ***Fludrocortisone*** - **Fludrocortisone** is a synthetic corticosteroid specifically designed to have potent **mineralocorticoid activity**, with significant sodium-retaining properties. - Its high affinity for **mineralocorticoid receptors** distinguishes it from other steroids and makes it effective in treating conditions like **Addison's disease** and **postural orthostatic tachycardia syndrome (POTS)** due to its ability to retain sodium and water. *DOCA (Deoxycorticosterone acetate)* - While **DOCA** does possess significant **mineralocorticoid activity** and was historically used for this purpose, **fludrocortisone** is generally considered to have a stronger and more sustained effect in clinical practice. - **DOCA's** mineralocorticoid potency is substantial but slightly less than that of **fludrocortisone** when compared on a weight basis for equivalent sodium retention. *Prednisolone* - **Prednisolone** is primarily a **glucocorticoid** with potent anti-inflammatory and immunosuppressive effects. - It has minimal to negligible **mineralocorticoid activity** and is not used for salt retention purposes. *Triamcinolone* - **Triamcinolone** is a potent **glucocorticoid** with a long duration of action and is known for its strong anti-inflammatory properties. - It has virtually no **mineralocorticoid activity**, making it unsuitable for conditions requiring sodium retention.

Q: Which statin is considered most potent based on mg-to-mg LDL reduction capability?

Rosuvastatin. ***Rosuvastatin*** - **Rosuvastatin** is known for its high potency, achieving significant **LDL-C reduction** at relatively low doses. - It is often considered the most potent statin on a **milligram-to-milligram basis**. *Simvastatin* - **Simvastatin** is a moderate-intensity statin, not as potent as rosuvastatin or atorvastatin in reducing LDL-C. - While effective, it typically requires higher doses to achieve comparable **LDL-C reductions** seen with high-potency statins. *Pravastatin* - **Pravastatin** is a hydrophilic statin, generally considered to be of lower potency compared to other statins like rosuvastatin and atorvastatin. - It is often used in patients with **hepatic dysfunction** due to its different metabolic profile but offers less aggressive **LDL-C reduction**. *Atorvastatin* - **Atorvastatin** is a high-intensity statin, very effective in reducing LDL-C, and often used for aggressive lipid lowering. - While highly potent, **atorvastatin** is generally considered slightly less potent than **rosuvastatin** on a mg-to-mg basis, though both are used for high-intensity lipid therapy.

Q: Which of the following medications does not interact with warfarin?

Benzodiazepines. ***Benzodiazepines*** - **Benzodiazepines** are generally considered safe to use with warfarin as they are extensively metabolized in the liver, but they do not typically alter the **cytochrome P450 enzymes** responsible for warfarin metabolism. - They also do not interfere with **vitamin K recycling** or **platelet function**, which are key mechanisms through which other drugs interact with warfarin. *Barbiturate* - **Barbiturates** are **potent inducers of hepatic enzymes**, particularly CYP2C9, which is responsible for metabolizing warfarin. - This enzyme induction leads to **increased warfarin metabolism**, reducing its anticoagulant effect and necessitating higher warfarin doses. *Oral contraceptive* - **Oral contraceptives** can **reduce the anticoagulant effect of warfarin** by inducing clotting factors or inhibiting warfarin metabolism. - This interaction can increase the risk of **thromboembolic events** in patients on warfarin. *Cephalosporins* - Certain **cephalosporins**, especially those with a **methylthiotetrazole (MTT) side chain** (e.g., Cefamandole, Cefoperazone, Moxalactam), can **inhibit vitamin K epoxide reductase**. - This inhibition leads to a **decrease in vitamin K-dependent clotting factors**, thus potentiating the anticoagulant effect of warfarin and increasing bleeding risk.

Question 1

Which enzyme is irreversibly inhibited by aspirin?

Accepted Answer

Cyclooxygenase

Answer

Lipooxygenase

Answer

Thromboxane synthase

Answer

Phospholipase

Question 2

Side effects of thiazide diuretics include all of the following except?

Accepted Answer

Hypocalcemia

Answer

Hypokalemia

Answer

Erectile dysfunction

Answer

Hyponatremia

Question 3

Which of the following is an intermediate-acting insulin?

Accepted Answer

NPH insulin

Answer

Insulin lispro

Answer

Insulin glargine

Answer

Regular insulin

Question 4

Long-term steroid ingestion leads to all of the following except:

Accepted Answer

Hypoglycemia

Answer

Avascular necrosis of head of femur

Answer

Growth retardation

Answer

Cataract

Question 5

Which antilipidemic drug reduces cholesterol levels by inhibiting cholesterol absorption?

Accepted Answer

Ezetimibe

Answer

Orlistat

Answer

Cholestyramine

Answer

Statins

Question 6

Which sulphonamide has the longest acting duration?

Accepted Answer

Sulphadoxine

Answer

Sulfadiazine

Answer

Sulfamethoxazole

Answer

Sulfamethiazole

Question 7

All are true about ciprofloxacin except?

Accepted Answer

More active at acidic pH

Answer

DNA gyrase inhibition

Answer

Contraindicated in pregnancy

Answer

Second generation fluoroquinolone

Question 8

Which steroid has the maximum mineralocorticoid activity?

Accepted Answer

Fludrocortisone

Answer

DOCA

Answer

Prednisolone

Answer

Triamcinolone

Question 9

Which statin is considered most potent based on mg-to-mg LDL reduction capability?

Accepted Answer

Rosuvastatin

Answer

Simvastatin

Answer

Pravastatin

Answer

Atorvastatin

Question 10

Which of the following medications does not interact with warfarin?

Accepted Answer

Benzodiazepines

Answer

Barbiturate

Answer

Oral contraceptive

Answer

Cephalosporins

NEET-PG 2012 — Pharmacology