NEET-PG 2015 - Pharmacology Practice Questions

Q: Which of the following medications is classified as a stool softener?

Docusates. **Docusates** - **Docusates** (e.g., docusate sodium, docusate calcium) are **stool softeners** that work by reducing the surface tension of stool, allowing water and lipids to penetrate. - This increases the water content in the stool, making it softer and easier to pass, which is particularly useful in preventing straining after surgery or in conditions like hemorrhoids. *Bran* - **Bran** is a **bulk-forming laxative**, a type of dietary fiber that adds mass to the stool. - It absorbs water in the intestines, which increases stool volume and stimulates bowel movements, but it does not directly soften the stool in the same way docusates do. *Senna* - **Senna** is a **stimulant laxative** that works by irritating the bowel wall to promote peristalsis and bowel evacuation. - While it can help move stool, it does not act primarily by softening it, and prolonged use can lead to dependency or electrolyte imbalances. *Phenolphthalein* - **Phenolphthalein** is a **stimulant laxative** that was historically used to promote bowel movements. - It is no longer widely used due to concerns about potential carcinogenicity and other adverse effects, and it does not function as a stool softener.

Q: Ximelagatran is used as ?

Anticoagulant. ***Anticoagulant*** - Ximelagatran is a **direct thrombin inhibitor**, meaning it directly blocks the action of thrombin, a key enzyme in the coagulation cascade. - By inhibiting thrombin, it prevents the formation of **fibrin clots**, thus acting as an anticoagulant. *Platelet inhibitor* - **Platelet inhibitors** prevent platelets from clumping together to form a clot, often by targeting pathways like ADP receptors or COX-1 enzyme. - Examples include **aspirin** and **clopidogrel**, which have different mechanisms of action than Ximelagatran. *Clot buster* - **Clot busters** are also known as thrombolytic agents, which actively dissolve existing blood clots. - They work by activating **plasminogen** to produce plasmin, an enzyme that breaks down fibrin. *Fibrinolytic* - **Fibrinolytics** are a class of drugs that enhance **fibrinolysis**, the natural process of breaking down blood clots. - **Thrombolytics** are a subset of fibrinolytic drugs used therapeutically to dissolve clots.

Q: Emtricitabine is classified as which of the following?

NRTI. ***NRTI*** - Emtricitabine is a **nucleoside reverse transcriptase inhibitor (NRTI)**, a class of antiretroviral drugs used in the treatment of **HIV infection**. - As an NRTI, it works by inhibiting the enzyme **reverse transcriptase**, which is crucial for the HIV virus to replicate its RNA into DNA. *Alkylating agent* - Alkylating agents are a type of **chemotherapy drug** that kill cancer cells by damaging their DNA. - They are primarily used in **cancer treatment**, not for viral infections like HIV. *Antimetabolite* - Antimetabolites are drugs that interfere with DNA and RNA synthesis, often used in **chemotherapy** to treat cancer or in immunosuppression. - While they can inhibit nucleic acid synthesis, this is a broad category, and emtricitabine's specific mechanism and classification are as an NRTI. *Integrase Inhibitor* - Integrase inhibitors are another class of **antiretroviral drugs** that block the HIV enzyme integrase, preventing the viral DNA from integrating into the host cell's DNA. - While an antiretroviral, emtricitabine has a different mechanism of action and belongs to the NRTI class.

Q: Which of the following combinations does not show synergistic action?

Penicillin plus tetracycline. ***Penicillin plus tetracycline*** - This combination is generally **antagonistic** or **indifferent**, not synergistic. Penicillin is a cell wall synthesis inhibitor that works best on actively growing bacteria, while tetracycline is a bacteriostatic protein synthesis inhibitor that can reduce bacterial growth, thereby diminishing penicillin's effect. - The combination is usually avoided as the **bacteriostatic action of tetracycline** can counteract the **bactericidal action of penicillin**, leading to reduced efficacy, especially in infections requiring rapid bacterial clearance. *Penicillin plus sulfonamide* - This combination can show synergism in some contexts, particularly as sulfonamides inhibit **folate synthesis**, while penicillin inhibits **cell wall synthesis**. - While not a classic synergistic pair for all infections, their mechanisms of action are distinct, and they can sometimes be used together, although specific synergistic effects are more limited compared to other pairs. *Streptomycin plus penicillin* - This is a classic example of **synergistic action**, particularly in conditions like **enterococcal endocarditis**. - Penicillin damages the bacterial cell wall, allowing **streptomycin** (an aminoglycoside) to more easily penetrate the cell and act on ribosomal targets, leading to enhanced bactericidal effect. *Rifampicin plus dapsone* - This combination is a cornerstone of **multi-drug therapy for leprosy**, demonstrating clear synergy against *Mycobacterium leprae*. - **Rifampicin** inhibits bacterial RNA synthesis, and **dapsone** inhibits folate synthesis, attacking different essential bacterial pathways which, when combined, are more effective and reduce the development of resistance.

Q: Which of the following is a characteristic of simvastatin?

Derived from fungal metabolite. ***Derived from fungal metabolite*** - **Simvastatin** and lovastatin are **naturally-derived statins** obtained from **fungal metabolites** (*Aspergillus terreus*), distinguishing them from synthetic statins like atorvastatin, rosuvastatin, and pravastatin [2]. - This is the **most distinguishing characteristic** for classification purposes, as it represents the drug's origin and places it in a specific subclass of HMG-CoA reductase inhibitors. - The discovery of fungal-derived statins led to the development of the entire statin drug class. *Prodrug requiring hepatic activation* - While **simvastatin** is a **lactone prodrug** requiring hepatic hydrolysis to its active beta-hydroxy acid form, this is a pharmacokinetic property shared with lovastatin [1]. - This is a characteristic but not the most distinguishing feature for classification. *Specific CYP3A4 substrate with high interaction potential* - **Simvastatin** is extensively metabolized by **CYP3A4**, leading to significant drug-drug interactions with CYP3A4 inhibitors (e.g., ketoconazole, erythromycin, grapefruit juice). - While clinically important, many drugs are CYP3A4 substrates, making this less distinctive as a defining characteristic. *Short half-life requiring evening dosing* - **Simvastatin** has a **short half-life** (2-3 hours) and is preferably administered in the evening because cholesterol synthesis is highest at night. - This is a dosing consideration based on pharmacokinetics rather than a fundamental distinguishing characteristic of the drug's identity.

Q: Among the following statins, which has the longest half-life?

Rosuvastatin. **Rosuvastatin** - **Rosuvastatin** has the longest half-life among the commonly used statins, approximately **19 hours**, allowing for consistent lipid-lowering effects. - Its prolonged presence in the body contributes to its effectiveness in reducing **LDL-C** at lower doses. *Pravastatin* - **Pravastatin** has a relatively short half-life of about **1.8 hours**, requiring daily dosing to maintain therapeutic concentrations. - Its hydrophilic nature means it is less likely to penetrate non-hepatic tissues, potentially reducing extrahepatic side effects. *Simvastatin* - **Simvastatin** has a short half-life of about **3 hours**, necessitating daily administration. - It is a **prodrug** that requires hepatic activation to its active beta-hydroxy acid form. *Lovastatin* - **Lovastatin** also has a short half-life, around **3 hours**, and is a **prodrug** like simvastatin. - It is often recommended to be taken in the evening due to the diurnal rhythm of cholesterol synthesis.

Q: Which antitubercular drug makes the patient non-infective the earliest?

Isoniazid (INH). ***Isoniazid (INH)*** - **Isoniazid** renders TB patients **non-infectious the fastest**, typically within **2-3 days** of starting treatment - It has the most **rapid bactericidal effect** against actively multiplying extracellular **Mycobacterium tuberculosis**, which are the primary organisms responsible for transmission - INH works by inhibiting **mycolic acid synthesis**, disrupting the bacterial cell wall of rapidly dividing bacilli - This makes it the most critical drug for **early infection control** and reducing community transmission *Rifampin* - While **rifampin** is highly bactericidal and has excellent sterilizing activity, it takes **slightly longer** than INH to render patients non-infectious - Rifampin is particularly effective against **semi-dormant organisms** and intracellular bacilli - It is the most important drug for **preventing relapse** and shortening treatment duration, but INH acts faster in reducing infectivity *Ethambutol* - **Ethambutol** is primarily **bacteriostatic**, inhibiting arabinosyl transferase and interfering with cell wall synthesis - Its main role is to **prevent emergence of drug resistance** rather than rapidly reducing bacterial load - Has minimal impact on early infectivity reduction *Pyrazinamide* - **Pyrazinamide** is most effective against **semi-dormant bacilli** within macrophages and in acidic environments - Its **sterilizing activity** helps shorten overall treatment duration but does not contribute significantly to rapid reduction in infectivity - Works slowly and is not bactericidal against actively multiplying extracellular organisms

Q: Thymidine is responsible for resistance to which antibiotic ?

Sulfonamide. ***Sulfonamide*** - **Thymidine** can contribute to **sulfonamide resistance** because sulfonamides interfere with **folate metabolism** and the subsequent synthesis of purines and pyrimidines, including thymidine. - An excess of thymidine can bypass the metabolic block caused by sulfonamides, allowing bacteria to continue DNA synthesis and grow. *Erythromycin* - **Erythromycin** resistance is primarily mediated by **methylation of ribosomal RNA**, which prevents the antibiotic from binding to the 50S ribosomal subunit. - It does not directly involve thymidine or the folate synthesis pathway. *Tetracycline* - Resistance to **tetracyclines** is commonly due to **efflux pumps** that actively pump the drug out of the bacterial cell or **ribosomal protection proteins** that prevent tetracycline binding. - Thymidine production or metabolism is not a mechanism of tetracycline resistance. *Nitrofurantoin* - **Nitrofurantoin** resistance typically involves **mutations** in bacterial enzymes (like **nitrofuran reductase**) that are responsible for activating the drug into its active form. - These mutations prevent the drug from becoming bactericidal, and thymidine does not play a role in this mechanism.

Q: Which of the following is not excreted by the kidney?

Moxifloxacin. ***Moxifloxacin*** - Moxifloxacin is primarily metabolized in the **liver** and excreted through bile and feces. - This characteristic makes it a suitable choice for patients with significant **renal impairment** as dose adjustments are generally not required. *Ciprofloxacin* - Ciprofloxacin is predominantly excreted by the **kidneys** through both glomerular filtration and tubular secretion. - Dose adjustments are crucial in patients with **renal dysfunction** to prevent accumulation and toxicity. *Ofloxacin* - Ofloxacin is largely excreted unchanged in the **urine**, making renal excretion its primary elimination pathway. - **Dose reduction** is necessary for patients with impaired renal function. *Levofloxacin* - Levofloxacin is primarily eliminated via **renal excretion**, with a significant portion appearing in the urine as unmetabolized drug. - Patients with **kidney disease** require appropriate dose adjustments.

Q: Quinine primarily acts on which stage of the Plasmodium life cycle?

Erythrocytic. ***Correct: Erythrocytic*** - Quinine primarily acts as a **blood schizonticide**, targeting the asexual erythrocytic stages of the *Plasmodium* parasite. - Its mechanism involves interfering with the parasite's ability to detoxify **heme**, leading to accumulation of toxic byproducts and parasite death within **red blood cells**. - This is why quinine is effective in treating **acute malaria attacks** during the symptomatic phase of the disease. *Incorrect: Exoerythrocytic* - The **exoerythrocytic stage** occurs in the liver, where sporozoites develop into merozoites. - Quinine has **minimal or no activity** against these liver stages, meaning it does not prevent initial infection or relapse from hepatic dormant forms (hypnozoites). - Drugs like **primaquine** target this stage. *Incorrect: Pre-erythrocytic* - The **pre-erythrocytic stage** is another term for the exoerythrocytic or liver stage of the parasite life cycle, occurring before the parasite enters red blood cells. - Medications that target this stage are known as **causal prophylactics**, which quinine is not. - Quinine has **no significant activity** at this stage. *Incorrect: None of the options* - This option is incorrect as quinine specifically targets the **erythrocytic stage**, making that option the correct answer. - Quinine's effectiveness in treating malaria stems from its action during the **symptomatic phase** of the disease, which corresponds to the erythrocytic cycle in red blood cells.

Question 1

Which of the following medications is classified as a stool softener?

Accepted Answer

Docusates

Answer

Bran

Answer

Senna

Answer

Phenolphthalein

Question 2

Ximelagatran is used as ?

Accepted Answer

Anticoagulant

Answer

Fibrinolytic

Answer

Platelet inhibitor

Answer

Clot buster

Question 3

Emtricitabine is classified as which of the following?

Accepted Answer

NRTI

Answer

Alkylating agent

Answer

Antimetabolite

Answer

Integrase Inhibitor

Question 4

Which of the following combinations does not show synergistic action?

Accepted Answer

Penicillin plus tetracycline

Answer

Streptomycin plus penicillin

Answer

Rifampicin plus dapsone

Answer

Penicillin plus sulfonamide

Question 5

Which of the following is a characteristic of simvastatin?

Accepted Answer

Derived from fungal metabolite

Answer

Specific CYP3A4 substrate with high interaction potential

Answer

Prodrug requiring hepatic activation

Answer

Short half-life requiring evening dosing

Question 6

Among the following statins, which has the longest half-life?

Accepted Answer

Rosuvastatin

Answer

Pravastatin

Answer

Simvastatin

Answer

Lovastatin

Question 7

Which antitubercular drug makes the patient non-infective the earliest?

Accepted Answer

Isoniazid (INH)

Answer

Ethambutol

Answer

Pyrazinamide

Answer

Rifampin

Question 8

Thymidine is responsible for resistance to which antibiotic ?

Accepted Answer

Sulfonamide

Answer

Erythromycin

Answer

Tetracycline

Answer

Nitrofurantoin

Question 9

Which of the following is not excreted by the kidney?

Accepted Answer

Moxifloxacin

Answer

Ciprofloxacin

Answer

Ofloxacin

Answer

Levofloxacin

Question 10

Quinine primarily acts on which stage of the Plasmodium life cycle?

Accepted Answer

Erythrocytic

Answer

Exoerythrocytic

Answer

Pre-erythrocytic

Answer

None of the options

NEET-PG 2015 — Pharmacology