NEET-PG 2013 - Pharmacology Practice Questions

Q: Muscarinic cholinergic receptors are seen at all sites, except?

Neuromuscular junction. ***Neuromuscular junction*** - The **neuromuscular junction** primarily contains **nicotinic cholinergic receptors**, not muscarinic receptors. - Activation of these nicotinic receptors by acetylcholine causes muscle contraction. *Stomach* - The stomach contains **muscarinic M3 receptors** which mediate gastric acid secretion and smooth muscle contraction. - Activation by acetylcholine via the vagus nerve promotes digestion. *CNS* - The **central nervous system** has various subtypes of **muscarinic receptors (M1-M5)** distributed throughout, playing roles in learning, memory, and motor control. - These receptors modulate neuronal excitability and neurotransmitter release. *Glands* - Most exocrine glands (e.g., salivary, lacrimal, sweat glands) are richly supplied with **muscarinic receptors**, primarily **M3**. - Activation leads to increased glandular secretion.

Q: Which of the following statements is true regarding omalizumab?

All of the options. ***All of the options*** is correct because each statement is true: **Anti-IgE** - Omalizumab is a **humanized monoclonal antibody** that specifically targets and binds to **free IgE** in the circulation - By binding free IgE, it prevents IgE from attaching to **high-affinity receptors** on mast cells and basophils - This reduces the allergic cascade and prevents release of inflammatory mediators **Given subcutaneously** - Omalizumab is administered via **subcutaneous injection** only - Dosing is typically every **2 to 4 weeks** based on patient's body weight and baseline IgE levels - Not available in oral or intravenous formulations for asthma treatment **Used as add-on therapy in moderate to severe asthma prophylaxis** - FDA approved as **add-on maintenance treatment** for patients aged ≥6 years with **moderate to severe persistent allergic asthma** - Indicated when asthma is **inadequately controlled** with inhaled corticosteroids - Reduces frequency of asthma exacerbations and improves asthma control - Also approved for chronic spontaneous urticaria All three statements accurately describe omalizumab's mechanism, administration route, and clinical indication, making **"All of the options"** the correct answer.

Q: Which dopamine receptor is known for its inhibitory action in the central nervous system?

Dopamine Receptor D2. ***Dopamine Receptor D2*** - The **D2 receptor** is a member of the D2-like family (D2, D3, D4), which are **G-protein coupled receptors** that inhibit adenylyl cyclase activity. - Its activation typically leads to a **decrease in neuronal excitability** and neurotransmitter release, providing an inhibitory effect in the CNS. *Dopamine Receptor D5* - The **D5 receptor** belongs to the D1-like family (D1, D5), which are **G-protein coupled receptors** that stimulate adenylyl cyclase activity. - Activation of D5 receptors typically leads to **excitatory effects** rather than inhibitory ones in the CNS. *No inhibitory dopamine receptor present* - This statement is incorrect as specific dopamine receptor subtypes, particularly the **D2-like family**, are well-established to exert inhibitory actions in the CNS. - These inhibitory effects are crucial for various physiological processes, including motor control and reward pathways. *Dopamine Receptor D1* - The **D1 receptor** is part of the D1-like family (D1, D5) and is known for its **excitatory effects** in the CNS. - Activation of D1 receptors leads to an **increase in intracellular cAMP** and generally enhances neuronal activity.

Q: Which of the following statements about clonidine is incorrect?

First line for AMI. ***First line for AMI*** - Clonidine is **not first-line** for **Acute Myocardial Infarction (AMI)** as it can cause **bradycardia** and **hypotension**, potentially worsening cardiac output. - First-line AMI treatments include **thrombolytics**, **antiplatelet agents** (aspirin), **beta-blockers**, and **ACE inhibitors** for optimal cardiac protection. *Alpha 2 receptor agonist* - Clonidine is indeed an **alpha-2 adrenergic receptor agonist** that acts centrally in the **medulla oblongata**. - It reduces **sympathetic outflow** from the CNS, leading to decreased **heart rate**, **blood pressure**, and **peripheral vascular resistance**. *Sudden withdrawal causes rebound hypertension* - Abrupt clonidine discontinuation causes dangerous **rebound hypertension** due to sudden loss of **sympathetic inhibition**. - **Gradual tapering** over 1-2 weeks is essential to prevent this potentially life-threatening complication. *Controls loose motions due to diabetic neuropathy* - Clonidine effectively treats **diabetic diarrhea** by stimulating **alpha-2 receptors** in the enteric nervous system. - It **slows intestinal transit** and **enhances fluid absorption**, making it useful for **autonomic neuropathy-related** gastrointestinal symptoms.

Q: Which of the following drugs is known to have low first pass metabolism?

Theophylline. ***Theophylline*** - **Theophylline** exhibits **low first-pass metabolism**, meaning a significant portion of the orally administered drug reaches systemic circulation unchanged. - This characteristic contributes to its relatively **high bioavailability** when given orally. *Lidocaine* - **Lidocaine** undergoes extensive **first-pass metabolism** in the liver, leading to very low oral bioavailability. - Due to this, it is typically administered **parenterally** (e.g., intravenously or topically) to achieve therapeutic concentrations. *Propranolol* - **Propranolol** is known for its significant **first-pass metabolism**, which results in a much lower bioavailability after oral administration compared to intravenous. - This extensive metabolism necessitates higher oral doses to achieve the same therapeutic effect as parenteral administration. *Morphine* - **Morphine** also undergoes substantial **first-pass metabolism** in the liver, where it is primarily glucuronidated. - This leads to a lower oral bioavailability compared to other routes of administration and contributes to a higher oral dose requirement.

Q: Which route of administration undergoes the maximum first pass metabolism?

Oral. ***Oral*** - Drugs administered orally are absorbed from the **gastrointestinal tract** and transported via the **portal vein** directly to the liver, where they undergo significant **first-pass metabolism** before reaching systemic circulation. - This hepatic metabolism can drastically reduce the **bioavailability** of the drug, requiring higher doses or alternative administration routes. *Intra-arterial* - This route delivers drugs directly into an **artery** supplying a target tissue or organ, largely bypassing systemic circulation and initial hepatic metabolism. - It is used for localized effects, such as **chemotherapy** for specific tumors, minimizing systemic exposure. *Rectal* - While a portion of rectally administered drugs may bypass the portal circulation by entering the **inferior and middle rectal veins**, a significant amount can still be absorbed into the superior rectal vein, which drains into the portal system. - This means rectal administration offers only **partial avoidance** of first-pass metabolism, making it less complete than IV or intra-arterial routes for bypassing the liver altogether. *Intravenous* - Drugs administered intravenously are delivered directly into the **systemic circulation**, completely bypassing the gastrointestinal tract and the liver's first-pass metabolism. - This route ensures **100% bioavailability** and rapid onset of action, as the drug immediately reaches its target.

Q: Which drug has the highest plasma protein binding?

Warfarin. ***Warfarin*** - **Warfarin** exhibits very **high plasma protein binding**, typically greater than 99%, primarily to albumin. - This high binding capacity means that only a small fraction of the drug is free and pharmacologically active. - Due to high protein binding, warfarin is susceptible to drug interactions when displaced from albumin. *Verapamil* - **Verapamil** has a relatively high plasma protein binding, around 90%, but it is not as high as warfarin. - Its binding is predominantly to **albumin** and alpha-1-acid glycoprotein. *Aspirin* - **Aspirin** (acetylsalicylic acid) has moderate plasma protein binding, usually between 50-90%, depending on the dosage. - It binds to **albumin** and can displace other protein-bound drugs. *GTN* - **Glyceryl trinitrate (GTN)** has moderate plasma protein binding, approximately 60%. - Its rapid onset and short duration of action are primarily due to its extensive first-pass metabolism and quick redistribution, rather than protein binding characteristics.

Q: What is the mechanism of metabolism for alcohol, aspirin, and phenytoin at high doses?

Zero order kinetics. ***Zero order kinetics*** - This mechanism occurs when the **metabolic enzymes become saturated at high drug concentrations**, leading to a constant amount (not a constant percentage) of drug being eliminated per unit time. - Alcohol, aspirin, and phenytoin are examples of drugs that exhibit **saturable metabolism**, transitioning from first-order to zero-order kinetics at higher doses. *First pass kinetics* - This describes the **metabolism of a drug by the liver or gut wall enzymes before it reaches systemic circulation** after oral administration. - While relevant to the oral bioavailability of these drugs, it does not describe the specific mechanism of elimination at high doses. *First order kinetics* - In this mechanism, a **constant fraction or percentage of the drug is eliminated per unit of time**, meaning the rate of elimination is directly proportional to the drug concentration. - Most drugs follow first-order kinetics at therapeutic doses because metabolizing enzymes are not saturated. *Second order kinetics* - This is a **less common pharmacokinetic model** where the rate of elimination is proportional to the square of the drug concentration or involves two reactants. - It does not typically describe the common elimination patterns of most drugs, including alcohol, aspirin, and phenytoin.

Q: Which of the following drugs is used for Smoking Cessation?

Bupropion. ***Bupropion*** - **Bupropion** is an antidepressant that is also approved as a smoking cessation aid. It works by inhibiting the reuptake of **dopamine** and **norepinephrine**, which can help reduce nicotine cravings and withdrawal symptoms. - It is often prescribed as a first-line pharmacotherapy for smoking cessation, with a typical treatment duration of 7-12 weeks. *Buprenorphine* - **Buprenorphine** is a partial opioid agonist primarily used to treat opioid addiction. It is not indicated for smoking cessation. - While it can help manage withdrawal symptoms from opioids, it has no direct mechanism of action that would reduce nicotine dependence or cravings. *Methadone* - **Methadone** is a full opioid agonist primarily used for the treatment of opioid use disorder (OUD) and chronic pain management. It is not used for smoking cessation. - Its mechanism involves binding to opioid receptors to prevent withdrawal symptoms and reduce cravings for other opioids. *Naltrexone* - **Naltrexone** is an opioid antagonist used primarily for the treatment of alcohol dependence and opioid use disorder. It is not indicated for smoking cessation. - It blocks the effects of opioids and reduces alcohol cravings, but does not affect nicotine pathways or dependence.

Q: Which of the following is not a cardioselective beta blocker?

Oxprenolol. ***Oxprenolol*** - **Oxprenolol** is a non-selective beta-blocker with **intrinsic sympathomimetic activity (ISA)**, meaning it blocks both β1 and β2 receptors and partially stimulates them. - Its non-selective action means it affects both the heart (β1) and other organs like the lungs (β2), making it less suitable for patients with respiratory conditions. *Nebivolol* - **Nebivolol** is a highly cardioselective beta-blocker that primarily blocks **β1 receptors** and also has **vasodilatory properties** due to nitric oxide release. - Its high selectivity translates to fewer β2-mediated side effects, such as bronchoconstriction. *Atenolol* - **Atenolol** is a **cardioselective beta-blocker** that predominantly blocks **β1 receptors** at therapeutic doses. - This selectivity makes it a common choice for cardiovascular conditions, reducing the risk of bronchospasm compared to non-selective agents. *Betaxolol* - **Betaxolol** is a **cardioselective beta-blocker** primarily used for the treatment of hypertension and glaucoma. - It selectively blocks **β1 adrenergic receptors**, minimizing effects on the lungs compared to non-selective beta-blockers.

Question 1

Muscarinic cholinergic receptors are seen at all sites, except?

Accepted Answer

Neuromuscular junction

Answer

Stomach

Answer

CNS

Answer

Glands

Question 2

Which of the following statements is true regarding omalizumab?

Accepted Answer

All of the options

Answer

Anti-IgE

Answer

Given subcutaneously

Answer

Used as add-on therapy in moderate to severe asthma prophylaxis

Question 3

Which dopamine receptor is known for its inhibitory action in the central nervous system?

Accepted Answer

Dopamine Receptor D2

Answer

Dopamine Receptor D5

Answer

No inhibitory dopamine receptor present

Answer

Dopamine Receptor D1

Question 4

Which of the following statements about clonidine is incorrect?

Accepted Answer

First line for AMI

Answer

Alpha 2 receptor agonist

Answer

Sudden withdrawal causes rebound hypertension

Answer

Controls loose motions due to diabetic neuropathy

Question 5

Which of the following drugs is known to have low first pass metabolism?

Accepted Answer

Theophylline

Answer

Lidocaine

Answer

Propranolol

Answer

Morphine

Question 6

Which route of administration undergoes the maximum first pass metabolism?

Accepted Answer

Oral

Answer

Intra-arterial

Answer

Rectal

Answer

Intravenous

Question 7

Which drug has the highest plasma protein binding?

Accepted Answer

Warfarin

Answer

Verapamil

Answer

Aspirin

Answer

GTN

Question 8

What is the mechanism of metabolism for alcohol, aspirin, and phenytoin at high doses?

Accepted Answer

Zero order kinetics

Answer

First pass kinetics

Answer

First order kinetics

Answer

Second order kinetics

Question 9

Which of the following drugs is used for Smoking Cessation?

Accepted Answer

Bupropion

Answer

Methadone

Answer

Buprenorphine

Answer

Naltrexone

Question 10

Which of the following is not a cardioselective beta blocker?

Accepted Answer

Oxprenolol

Answer

Nebivolol

Answer

Atenolol

Answer

Betaxolol

NEET-PG 2013 — Pharmacology