NEET-PG 2015 - Pharmacology Practice Questions

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: Emtricitabine is a/an:

Nucleoside reverse transcriptase inhibitor (NRTI). ***Nucleoside reverse transcriptase inhibitor (NRTI)*** - **Emtricitabine** is a synthetic nucleoside analog that inhibits the activity of HIV-1 **reverse transcriptase**, an enzyme essential for viral replication. - It works by being phosphorylated to its active triphosphate form, which then competes with natural deoxycytidine triphosphate for incorporation into the viral DNA, leading to **chain termination**. *Alkylating agent* - **Alkylating agents** are a class of antineoplastic drugs that work by adding an alkyl group to DNA, forming a covalent bond that interferes with DNA replication and transcription. - They are primarily used in **cancer chemotherapy**, not as antiviral agents for HIV. *Mitotic inhibitor* - **Mitotic inhibitors** are drugs that interfere with cell division (mitosis) by targeting microtubules, either inhibiting their polymerization or depolymerization. - These agents are also used in **cancer treatment** to prevent rapidly dividing cells from completing mitosis. *None of the options* - This option is incorrect because **emtricitabine** clearly belongs to the class of **nucleoside reverse transcriptase inhibitors**.

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: In patients undergoing INH therapy, which group is least likely to develop neuropathy?

Fast acetylators. ***Fast acetylators*** - **Fast acetylators** metabolize INH more quickly, leading to lower systemic drug levels and thus a reduced risk of adverse effects like neuropathy. - Neuropathy associated with INH is primarily due to **pyridoxine (vitamin B6) depletion**, which is less pronounced if the drug is rapidly cleared. *Having malnutrition* - **Malnutrition** often involves deficiencies in essential vitamins, including vitamin B6, which is crucial for preventing INH-induced neuropathy. - Patients with poor nutritional status are at a **higher risk** of developing neuropathy during INH therapy due to pre-existing vitamin B6 depletion. *Alcoholics* - **Alcoholism** is strongly associated with deficiencies in various B vitamins, particularly **pyridoxine (vitamin B6)**, due to poor diet and impaired absorption. - This pre-existing deficiency makes alcoholics **highly susceptible** to INH-induced neuropathy. *Vitamin B complex deficiency* - A **deficiency in vitamin B complex**, especially pyridoxine (B6), is a known risk factor for INH-induced neuropathy. - Isoniazid interferes with **pyridoxine metabolism**, and those with pre-existing deficiency are more vulnerable to this adverse effect.

Q: Which of the following drugs is not used for the treatment of H. Pylori?

Domperidone. ***Correct: Domperidone*** - Domperidone is a **prokinetic drug** used to treat nausea, vomiting, and gastric motility disorders, but it has **no direct antibacterial activity** against *H. pylori*. - It works by blocking **dopamine receptors** in the chemoreceptor trigger zone and peripherally. - Therefore, it is **NOT used for *H. pylori* eradication**. *Incorrect: Bismuth* - **Bismuth subsalicylate** is a key component of **quadruple therapy** for *H. pylori* eradication, particularly in cases of antibiotic resistance or treatment failure. - It has **bactericidal effects** against *H. pylori*, disrupts its cell wall, and inhibits its adherence to the gastric mucosa. *Incorrect: Amoxicillin* - **Amoxicillin** is a penicillin-class antibiotic commonly used in various *H. pylori* eradication regimens, including **triple therapy**. - It acts by **inhibiting bacterial cell wall synthesis**, leading to bacterial lysis. *Incorrect: Clarithromycin* - **Clarithromycin** is a macrolide antibiotic frequently included in standard **triple therapy** for *H. pylori* eradication. - It inhibits **bacterial protein synthesis** by binding to the 50S ribosomal subunit.

Q: Which of the following is the longest acting carbapenem?

Ertapenem. ***Ertapenem*** - **Ertapenem** has the **longest half-life** among the carbapenems, allowing for once-daily dosing. - Its prolonged action is due to its **chemical structure**, which provides high protein binding and reduced renal clearance compared to other carbapenems. *Imipenem* - **Imipenem** has a **relatively short half-life** and requires co-administration with cilastatin to prevent its renal metabolism by dehydropeptidase-1. - Its short duration of action necessitates **frequent dosing**, typically every 6 to 8 hours. *Meropenem* - **Meropenem** has a **shorter half-life** than ertapenem, generally requiring dosing every 8 hours. - Although it does not require cilastatin, its pharmacokinetic profile is not as extended as ertapenem's. *Doripenem* - **Doripenem** also has a **shorter half-life** than ertapenem, necessitating administration every 8 hours. - Its spectrum of activity is similar to meropenem, but it does not offer the same extended duration of action.

Q: Which ACE inhibitor is safe in renal failure?

Benazepril. ***Benazepril*** - Among the listed ACE inhibitors, benazepril has the **most favorable excretion profile** in renal failure with approximately **50% renal and 50% hepatic elimination** (dual excretion pathway). - This balanced elimination reduces the risk of drug accumulation compared to predominantly renally excreted ACE inhibitors. - While dose adjustment may still be needed in **severe renal impairment**, benazepril is considered the **safest option among those listed** for patients with renal dysfunction. - **Note:** Fosinopril (not listed here) has true 50/50 dual elimination and requires no dose adjustment in renal failure, making it the ideal choice in clinical practice. *Captopril* - This ACE inhibitor undergoes predominantly **renal excretion (95%)** as unchanged drug and metabolites. - Requires significant **dose reduction** in renal failure to prevent accumulation and adverse effects including **hyperkalemia** and **hypotension**. - Less safe than benazepril in renal impairment due to heavy dependence on renal elimination. *Enalapril* - Enalapril is a prodrug converted to **enalaprilat**, with approximately **90% renal excretion**. - Dose adjustment is mandatory based on **creatinine clearance** in patients with renal failure. - Higher risk of accumulation and toxicity compared to dual-elimination ACE inhibitors like benazepril.

Q: Alkaline diuresis in drug poisoning is not done in?

Morphine. ***Morphine*** - **Morphine** is an **alkaline drug**, so its elimination is actually enhanced by **acidification of the urine**, not alkalinization. - Alkaline diuresis would decrease the ionization of morphine in the renal tubules, leading to **increased reabsorption** and reduced excretion. *Aspirin* - **Aspirin (acetylsalicylic acid)** is an **acidic drug**, and **alkaline diuresis** is effective in increasing its excretion by trapping the ionized form in the renal tubules. - This process prevents reabsorption and promotes clearance, which is a standard treatment for aspirin overdose. *Methotrexate* - **Methotrexate** is a **weak organic acid**, and **alkaline diuresis** is crucial in reducing its toxicity, especially in high-dose therapy. - By increasing urine pH, the renal elimination of methotrexate is significantly enhanced, preventing kidney damage and systemic accumulation. *Phenobarbitone* - **Phenobarbitone** is a **weak acid**, and **alkaline diuresis** is a well-established method to increase its renal excretion in cases of overdose. - Alkalinization of the urine promotes the ionization of phenobarbitone, reducing its reabsorption by the renal tubules and accelerating its elimination.

Q: Permission from DCGI [Drug controller general, India] is needed before which phase of drug trial?

Phase 3. ***Phase 3*** - Permission from the **DCGI (Drug Controller General of India)** is mandatory before initiating **Phase 3** clinical trials as per **Schedule Y** of the Drugs and Cosmetics Rules. - Phase 3 trials involve **large-scale studies in Indian patients** to establish efficacy and safety in the target population, requiring explicit regulatory approval. - This is the critical regulatory checkpoint where DCGI evaluates the Phase 1 and 2 data before allowing widespread testing in Indian subjects. *Phase 1* - Phase 1 trials can be conducted after approval from the **Institutional Ethics Committee (IEC)** without requiring prior DCGI permission. - These trials in healthy volunteers focus on safety, pharmacokinetics, and dose-ranging studies. - DCGI is informed but explicit permission is not mandatory at this stage. *Phase 2* - Phase 2 trials also proceed with **IEC approval** and do not require prior DCGI permission. - These trials evaluate therapeutic efficacy and dose determination in a limited number of patients. - Results from Phase 2 are submitted to DCGI when seeking Phase 3 approval. *Phase 4* - Phase 4 trials are **post-marketing surveillance** studies conducted after drug approval. - These are conducted under the Post-Marketing Surveillance (PMS) framework. - While regulatory oversight exists, these are not pre-market trials requiring permission to initiate.

Question 1

Emtricitabine is classified as which of the following?

Accepted Answer

NRTI

Answer

Alkylating agent

Answer

Antimetabolite

Answer

Integrase Inhibitor

Question 2

Emtricitabine is a/an:

Accepted Answer

Nucleoside reverse transcriptase inhibitor (NRTI)

Answer

Alkylating agent

Answer

Mitotic inhibitor

Answer

None of the options

Question 3

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 4

In patients undergoing INH therapy, which group is least likely to develop neuropathy?

Accepted Answer

Fast acetylators

Answer

Having malnutrition

Answer

Alcoholics

Answer

Vitamin B complex deficiency

Question 5

Which of the following drugs is not used for the treatment of H. Pylori?

Accepted Answer

Domperidone

Answer

Bismuth

Answer

Clarithromycin

Answer

Amoxicillin

Question 6

Which of the following is the longest acting carbapenem?

Accepted Answer

Ertapenem

Answer

Imipenem

Answer

Meropenem

Answer

Doripenem

Question 7

Which ACE inhibitor is safe in renal failure?

Accepted Answer

Benazepril

Answer

Captopril

Answer

Enalapril

Answer

None of the options

Question 8

Which statement best describes first-order kinetics in pharmacokinetics?

Accepted Answer

Elimination of the drug is proportional to the serum concentration

Answer

Absorption of the drug is independent of the serum concentration

Answer

Absorption of the drug is proportional to the serum concentration

Answer

Elimination of the drug is independent of the serum concentration

Question 9

Alkaline diuresis in drug poisoning is not done in?

Accepted Answer

Morphine

Answer

Aspirin

Answer

Phenobarbitone

Answer

Methotrexate

Question 10

Permission from DCGI [Drug controller general, India] is needed before which phase of drug trial?

Accepted Answer

Phase 3

Answer

Phase 1

Answer

Phase 2

Answer

Phase 4

NEET-PG 2015 — Pharmacology