NEET-PG 2015 - Pharmacology Practice Questions

Q: Which of the following are CYP3A inhibitors?

Both a and c. ***Both a and c (Ritonavir and Verapamil)*** - **Ritonavir** is a **potent CYP3A4 inhibitor**, one of the strongest known, commonly used as a pharmacokinetic booster for other protease inhibitors to increase their bioavailability - **Verapamil** is a **calcium channel blocker** that acts as a **moderate CYP3A4 inhibitor**, leading to clinically significant drug interactions requiring dose adjustments - Both drugs have **clinically relevant and well-established** CYP3A4 inhibitory effects *Ritonavir alone* - While correct that Ritonavir is a potent CYP3A4 inhibitor, this option is incomplete as it excludes Verapamil - Ritonavir's inhibitory effect is so strong that it can increase plasma concentrations of co-administered CYP3A4 substrates by several-fold *Amiodarone* - Amiodarone is primarily a **potent inhibitor of CYP2C9, CYP2D6, and P-glycoprotein** - While it does have **weak to moderate CYP3A4 inhibitory activity**, this effect is **less clinically significant** compared to its effects on other CYP enzymes - In the context of clinically important CYP3A4 inhibitors, Ritonavir and Verapamil are more relevant examples *Verapamil alone* - While correct that Verapamil is a CYP3A4 inhibitor, this option is incomplete as it excludes Ritonavir - Verapamil can increase plasma concentrations of drugs like simvastatin, cyclosporine, and other CYP3A4 substrates

Q: Regarding the concepts of efficacy and potency of a drug, which of the following statements is FALSE?

ED50 of the drug corresponds to efficacy. ***ED50 of the drug corresponds to efficacy*** - **ED50** (median effective dose) is the dose at which 50% of individuals exhibit the specified effect; it quantifies **potency**, not efficacy. - **Efficacy** refers to the maximum effect a drug can produce, while potency refers to the amount of drug needed to produce an effect. *In a clinical setup, efficacy is more important than potency* - **Efficacy** determines the maximal therapeutic benefit a drug can achieve for a patient, making it crucial for clinical outcomes. - While **potency** influences the dose required, a highly potent drug that is not very efficacious may not be clinically useful. *Drugs that produce a similar pharmacological effect can have different levels of efficacy* - Two drugs might act on the same receptor but elicit different maximal responses, indicating varying **efficacy**. - For example, a **partial agonist** and **full agonist** interacting with the same receptor will have different efficacies. *In the log dose response curve, the height of the curve corresponds with efficacy* - The **maximal response** or plateau of the dose-response curve represents the **efficacy** of a drug. - A higher plateau on the curve indicates a drug with greater intrinsic activity achieving a larger effect.

Q: Volume of distribution of a drug is 500 ml and target concentration of drug in blood is 5 g/L. 20% of administered drug is reached to systemic circulation. What will be the loading dose of that drug -

12.5 gm. ***12.5 gm*** - The formula for loading dose (LD) is: LD = (Target Concentration × Volume of Distribution) / Bioavailability. - Given: Target Concentration = 5 g/L, Volume of Distribution = 500 mL = 0.5 L, Bioavailability = 20% = 0.2. - So, LD = (5 g/L × 0.5 L) / 0.2 = 2.5 g / 0.2 = **12.5 g**. *1 gm* - This value would be obtained if the target concentration was 2 g/L with 100% bioavailability, or if the calculation incorrectly handled the volume or bioavailability factor. - It does not account for the specified **bioavailability of 20%** or the given target concentration and volume of distribution. *5 gm* - This result would be obtained if the bioavailability was assumed to be 50% (LD = 2.5 g / 0.5 = 5 g), or if the volume of distribution was incorrectly used in the calculation. - This option does not correctly factor in the **20% bioavailability** of the administered drug. *25 gm* - This value would result from mistakes such as dividing by bioavailability of 10% instead of 20% (LD = 2.5 g / 0.1 = 25 g), or by multiplying bioavailability instead of dividing by it. - This answer significantly **overestimates** the required dose, which could lead to drug toxicity.

Q: High volume of distribution is primarily determined by:

High lipid solubility. ***High lipid solubility***- Highly **lipid-soluble** drugs readily cross biological membranes and distribute extensively into tissues, including adipose tissue, CNS, and intracellular compartments, leading to a **high volume of distribution (Vd)** [1, 2].- This property allows the drug to move out of the bloodstream and into various body compartments, increasing the apparent volume in which the drug is dissolved [1].*High plasma protein binding*- **High plasma protein binding** generally **restricts** drug distribution to tissues because only the **unbound (free) fraction** can diffuse across capillary membranes into interstitial fluid and cells [1].- This typically leads to a **lower Vd**, as the drug is largely retained within the plasma compartment.*Elimination rate*- The **elimination rate** determines how quickly the drug is removed from the body, affecting the **duration of action** rather than the extent of distribution.- It influences drug concentration changes over time but does not directly determine the physical space (volume) into which the drug distributes.*Half-life of the drug*- The **half-life (t½)** is the time required for drug concentration to reduce by half, and it is **determined by** both Vd and clearance (t½ = 0.693 × Vd/CL).- Half-life is a **consequence** of Vd and clearance, not a primary determinant of how widely a drug distributes [3].

Q: Which of the following conditions is not associated with an increased risk of neuropathy caused by Isoniazid (INH)?

Hyperthyroidism. ***Hyperthyroidism*** - **Hyperthyroidism** is not typically associated with an increased risk of isoniazid-induced neuropathy. The neuropathy due to INH is primarily linked to **pyridoxine (vitamin B6) deficiency**. - While hyperthyroidism can cause its own set of neurological symptoms, it does not directly impair pyridoxine metabolism or exacerbate INH's neurotoxic effects. *Uremia* - **Uremia** (renal failure) can increase the risk of INH-induced neuropathy due to impaired drug excretion, leading to higher plasma concentrations of INH and its metabolites. - Patients with uremia often have compromised nutritional status and may experience vitamin deficiencies, further contributing to pyridoxine depletion. *Diabetes mellitus* - **Diabetes mellitus** is a significant risk factor for INH-induced neuropathy because it is an independent cause of **peripheral neuropathy** itself, making patients more susceptible to additional nerve damage. - Diabetic patients may also have altered pyridoxine metabolism or suboptimal nutritional intake, predisposing them to INH toxicity. *Poor nutrition* - **Poor nutrition**, particularly malabsorption or inadequate dietary intake, directly contributes to **pyridoxine (vitamin B6) deficiency**. - Isoniazid's mechanism of neurotoxicity involves interfering with pyridoxine metabolism, so pre-existing deficiency significantly increases the risk of neuropathy.

Q: Idoxuridine is used for treatment of?

HSV. ***HSV*** - **Idoxuridine** is a **pyrimidine analog** that inhibits viral DNA synthesis, making it effective against **herpes simplex virus (HSV)** infections, particularly **herpes keratitis** (ophthalmic use). - Its mechanism involves being incorporated into viral DNA, leading to errors in replication and transcription. - It is applied **topically** for ocular HSV infections due to systemic toxicity concerns. *Influenza* - **Idoxuridine** is not active against **influenza viruses**. - **Antiviral drugs** like **oseltamivir** or **zanamivir** are typically used for influenza treatment. *RSV* - **Idoxuridine** is not indicated for the treatment of **respiratory syncytial virus (RSV)**. - **Ribavirin** is the primary antiviral agent used for severe RSV infections, especially in immunocompromised patients. *HIV* - **Idoxuridine** has no significant activity against **human immunodeficiency virus (HIV)**. - **Antiretroviral therapy (ART)**, a combination of drugs targeting various stages of the HIV life cycle, is used for HIV treatment.

Q: What is the best method for treating methanol poisoning?

Fomepizole. ***Fomepizole*** - **Fomepizole** (Antizol) is a potent inhibitor of **alcohol dehydrogenase**, the enzyme responsible for metabolizing methanol into toxic metabolites like formic acid [1]. - By inhibiting this enzyme, fomepizole prevents the formation of these harmful metabolites, thus halting the progression of methanol toxicity and reducing mortality [1]. - It is the **gold standard** antidote for methanol poisoning. *Calcium gluconate* - **Calcium gluconate** is primarily used to treat **hypocalcemia** and magnesium toxicity. - It has no role in the direct treatment or detoxification of methanol poisoning. *Deferoxamine* - **Deferoxamine** is a **chelating agent** used to treat **iron toxicity** by binding to iron and facilitating its excretion [3]. - It is not effective for methanol poisoning as it does not interact with methanol or its toxic metabolites. *BAL* - **BAL** (British Anti-Lewisite, dimercaprol) is a chelating agent primarily used for poisoning by **heavy metals** such as arsenic, mercury, and gold [2]. - It has no therapeutic role in methanol poisoning, which involves a different toxicological mechanism.

Q: Interstitial nephritis is associated with all of the following medications except:

INH. ***INH*** - **Isoniazid (INH)** is primarily associated with **hepatotoxicity** (liver damage) and **peripheral neuropathy**, not typically interstitial nephritis. - While many drugs can rarely cause various adverse effects, INH is not a recognized common cause of **drug-induced interstitial nephritis**. *Beta-lactam antibiotics* - **Beta-lactam antibiotics**, including penicillins and cephalosporins, are among the most common causes of **drug-induced acute interstitial nephritis (AIN)**. - AIN is an **allergic hypersensitivity reaction** characterized by inflammation of the kidney's tubules and interstitium. *Diuretics* - Certain **diuretics**, particularly **thiazide diuretics** and **loop diuretics**, have been implicated in causing **acute interstitial nephritis**. - The mechanism is thought to be an **allergic or hypersensitivity reaction** within the renal tubules and interstitium. *Allopurinol* - **Allopurinol**, used to treat gout and hyperuricemia, is a known cause of **drug-induced acute interstitial nephritis**. - Renal involvement with allopurinol can range from mild tubular dysfunction to severe **acute kidney injury** due to AIN.

Q: What is the classification of Lorcaserin?

Anti-obesity. ***Anti-obesity*** - Lorcaserin is a selective **serotonin 5-HT₂C receptor agonist** that works by promoting satiety and reducing food intake. - It is prescribed as a long-term treatment for **weight management** in adults who are obese or overweight with at least one weight-related comorbidity. *Anti-anxiety* - Anti-anxiety medications, such as **benzodiazepines** or **SSRIs**, primarily target neurotransmitters like GABA or serotonin 5-HT₁A receptors to reduce anxiety symptoms. - Lorcaserin's primary mechanism of action is distinct, focusing on the 5-HT₂C receptor for appetite regulation, not anxiety. *Anti-smoking* - Anti-smoking medications, like **varenicline** or **bupropion**, are designed to reduce nicotine cravings and withdrawal symptoms. - Their mechanisms often involve nicotinic acetylcholine receptors or dopamine and norepinephrine reuptake inhibition, which differs from lorcaserin's action. *Anti-helminthic* - Anti-helminthic drugs are used to treat **parasitic worm infections** by paralyzing or killing the worms. - Common examples include **albendazole** or **mebendazole**, which have no relation to appetite control or obesity treatment.

Q: What is the half-life of nicotine in blood?

2 hours. ***2 hours*** - Nicotine has a **relatively short half-life** in the blood, typically around 2 hours, contributing to frequent dosing in tobacco users. - This rapid elimination means that nicotine concentrations decrease significantly within a few hours after the last dose, leading to **withdrawal symptoms** or cravings. *15 minutes* - A 15-minute half-life would imply an **extremely rapid clearance**, which is not characteristic of nicotine. - Such quick elimination would make it very difficult to maintain consistent drug levels and would lead to immediate, intense withdrawal. *5 hours* - While longer than the actual half-life, 5 hours is still within the realm of substances requiring **multiple daily doses**. - However, it would mean nicotine levels would remain elevated for a longer period than observed, potentially delaying withdrawal. *24 hours* - A 24-hour half-life would mean nicotine would accumulate significantly in the body with daily use, leading to **prolonged effects** and a much slower decline in concentrations after cessation. - This half-life is typical for drugs designed for **once-daily dosing**, which is not the case for nicotine.

Question 1

Which of the following are CYP3A inhibitors?

Accepted Answer

Both a and c

Answer

Ritonavir

Answer

Amiodarone

Answer

Verapamil

Question 2

Regarding the concepts of efficacy and potency of a drug, which of the following statements is FALSE?

Accepted Answer

ED50 of the drug corresponds to efficacy

Answer

Drugs that produce a similar pharmacological effect can have different levels of efficacy

Answer

In a clinical setup, efficacy is more important than potency

Answer

In the log dose response curve, the height of the curve corresponds with efficacy

Question 3

Volume of distribution of a drug is 500 ml and target concentration of drug in blood is 5 g/L. 20% of administered drug is reached to systemic circulation. What will be the loading dose of that drug -

Accepted Answer

12.5 gm

Answer

1 gm

Answer

5 gm

Answer

25 gm

Question 4

High volume of distribution is primarily determined by:

Accepted Answer

High lipid solubility

Answer

High plasma protein binding

Answer

Elimination rate

Answer

Half-life of the drug

Question 5

Which of the following conditions is not associated with an increased risk of neuropathy caused by Isoniazid (INH)?

Accepted Answer

Hyperthyroidism

Answer

Uremia

Answer

Diabetes mellitus

Answer

Poor nutrition

Question 6

Idoxuridine is used for treatment of?

Accepted Answer

HSV

Answer

Influenza

Answer

RSV

Answer

HIV

Question 7

What is the best method for treating methanol poisoning?

Accepted Answer

Fomepizole

Answer

Calcium gluconate

Answer

BAL

Answer

Deferoxamine

Question 8

Interstitial nephritis is associated with all of the following medications except:

Accepted Answer

INH

Answer

Diuretics

Answer

Allopurinol

Answer

Beta-lactam antibiotics

Question 9

What is the classification of Lorcaserin?

Accepted Answer

Anti-obesity

Answer

Anti-anxiety

Answer

Anti-smoking

Answer

Anti-helminthic

Question 10

What is the half-life of nicotine in blood?

Accepted Answer

2 hours

Answer

15 minutes

Answer

5 hours

Answer

24 hours

NEET-PG 2015 — Pharmacology