Which of the following medications is classified as a stool softener?
What is the drug of choice for drug-induced peptic ulcer?
Ximelagatran is used as ?
Which of the following is a characteristic of simvastatin?
Among the following statins, which has the longest half-life?
Which antitubercular drug makes the patient non-infective the earliest?
Thymidine is responsible for resistance to which antibiotic ?
Which of the following is not excreted by the kidney?
Which of the following is a primary use of Levamisole?
Quinine primarily acts on which stage of the Plasmodium life cycle?
NEET-PG 2015 - Pharmacology NEET-PG Practice Questions and MCQs
Question 61: Which of the following medications is classified as a stool softener?
- A. Bran
- B. Senna
- C. Phenolphthalein
- D. Docusates (Correct Answer)
Explanation: **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.
Question 62: What is the drug of choice for drug-induced peptic ulcer?
- A. Prostaglandin analogues
- B. H2-receptor antagonists
- C. Proton pump inhibitors (Correct Answer)
- D. Antacids
Explanation: ***Proton pump inhibitors*** - **PPIs** are the most effective agents for treating and preventing **NSAID-induced peptic ulcers** by profoundly suppressing gastric acid secretion. - They provide **rapid symptom relief** and promote ulcer healing by creating an environment conducive to mucosal repair. *Prostaglandin analogues* - **Misoprostol**, a prostaglandin E1 analogue, can prevent NSAID-induced ulcers, but its use is limited by **gastrointestinal side effects** such as diarrhea and abdominal cramping. - While they protect the gastric mucosa, their efficacy in healing established ulcers is generally **inferior to PPIs**. *H2-receptor antagonists* - **H2-blockers** are effective in reducing gastric acid, but they are **less potent** than PPIs and typically do not heal **gastric ulcers** as effectively, especially those induced by NSAIDs. - They are more commonly used for preventing **duodenal ulcers** and managing symptoms of GERD. *Antacids* - Antacids provide **immediate, temporary relief** of ulcer symptoms by neutralizing existing stomach acid. - They do not address the underlying pathology or promote **ulcer healing** and are therefore not considered the drug of choice for treatment.
Question 63: Ximelagatran is used as ?
- A. Anticoagulant (Correct Answer)
- B. Fibrinolytic
- C. Platelet inhibitor
- D. Clot buster
Explanation: ***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.
Question 64: Which of the following is a characteristic of simvastatin?
- A. Specific CYP3A4 substrate with high interaction potential
- B. Derived from fungal metabolite (Correct Answer)
- C. Prodrug requiring hepatic activation
- D. Short half-life requiring evening dosing
Explanation: ***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.
Question 65: Among the following statins, which has the longest half-life?
- A. Pravastatin
- B. Simvastatin
- C. Lovastatin
- D. Rosuvastatin (Correct Answer)
Explanation: **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.
Question 66: Which antitubercular drug makes the patient non-infective the earliest?
- A. Ethambutol
- B. Pyrazinamide
- C. Isoniazid (INH) (Correct Answer)
- D. Rifampin
Explanation: ***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
Question 67: Thymidine is responsible for resistance to which antibiotic ?
- A. Erythromycin
- B. Sulfonamide (Correct Answer)
- C. Tetracycline
- D. Nitrofurantoin
Explanation: ***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.
Question 68: Which of the following is not excreted by the kidney?
- A. Ciprofloxacin
- B. Ofloxacin
- C. Moxifloxacin (Correct Answer)
- D. Levofloxacin
Explanation: ***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.
Question 69: Which of the following is a primary use of Levamisole?
- A. Immunostimulant
- B. Antihelminthic (Correct Answer)
- C. None of the options
- D. Immunomodulator
Explanation: ***Antihelminthic*** - Levamisole is **primarily classified as an antihelminthic drug**, used to treat parasitic worm infections. - It acts as a **nicotinic receptor agonist** in nematodes, causing spastic paralysis of the worms, leading to their expulsion. - It was historically used in humans for treating ascariasis and hookworm infections, and is still used in **veterinary medicine** for deworming livestock. - This is its **primary pharmacological classification** in standard medical textbooks. *Immunomodulator* - Levamisole does have **immunomodulatory properties** that were discovered secondary to its antihelminthic use. - It was used as **adjuvant therapy in colon cancer** (with 5-FU) to enhance immune response. - However, this is a **secondary use**, not its primary classification, and has been largely discontinued due to severe side effects like agranulocytosis. *Immunostimulant* - While levamisole can stimulate certain aspects of cell-mediated immunity, this overlaps with its immunomodulatory effects. - This is **not its primary pharmacological classification** - it remains primarily an antihelminthic agent. *None of the options* - This is incorrect because **antihelminthic** is clearly the primary and correct classification of levamisole in pharmacology. - Its antihelminthic action was its original and primary therapeutic application.
Question 70: Quinine primarily acts on which stage of the Plasmodium life cycle?
- A. Exoerythrocytic
- B. Pre-erythrocytic
- C. Erythrocytic (Correct Answer)
- D. None of the options
Explanation: ***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.