General Pharmacology Practice Questions

Q: All the following are ligand-gated ion channels EXCEPT:

H2 receptor. ***H2 receptor*** - The **H2 receptor** is a classic example of a **G-protein coupled receptor (GPCR)**, specifically linked via **Gs protein** to adenylate cyclase, not a ligand-gated ion channel. - It mediates gastric acid secretion through the activation of **cAMP** secondary messenger pathways rather than direct ion flux. *5-HT3 receptor* - The **5-HT3 receptor** is a unique serotonin receptor that functions as a **ligand-gated ion channel** (ionotropic). - It is permeable to cations like **Na+**, **K+**, and **Ca2+**, leading to rapid depolarization. *GABA-A receptor* - The **GABA-A receptor** is a well-known **ligand-gated ion channel** that allows the influx of **chloride ions** (Cl-). - Upon binding GABA, it induces an **inhibitory postsynaptic potential (IPSP)**, leading to neuronal hyperpolarization. *Nicotinic receptor* - The **nicotinic acetylcholine receptor (nAChR)** is the prototypical ligand-gated ion channel found at the **neuromuscular junction**. - It opens a non-selective cation channel upon the binding of **acetylcholine**, triggering muscle fiber depolarization.

Q: A 34-year-old male with opioid dependence enrolled in a maintenance programme presents to the emergency department with palpitations and two witnessed syncopal episodes over the past 24 hours. His only medication was started 6 weeks ago at a community addiction clinic. Baseline ECG on enrolment was normal. The on-call resident records the ECG shown in Image 1. Which drug is most likely responsible for the rhythm disturbance seen?

A. Methadone. ***A. Methadone*** - **Methadone** is a long-acting opioid agonist known to inhibit **hERG (IKr) potassium channels**, which leads to **QTc prolongation**. - This prolongation increases the risk of **Torsades de Pointes**, a polymorphic ventricular tachycardia that correlates with the patient's palpitations and **syncope**. *B. Buprenorphine* - **Buprenorphine** is a partial mu-opioid agonist frequently used for maintenance but has a significantly lower risk of **QT prolongation** compared to methadone. - It is generally considered a safer alternative for patients with cardiovascular risk factors or those requiring high-dose **opioid substitution therapy**. *C. Naltrexone* - **Naltrexone** is an opioid antagonist used for total relapse prevention and has no known clinical association with **ventricular arrhythmias** or ECG changes. - Because it does not affect cardiac ion channels, it would not cause the **rhythm disturbance** seen in a patient with a normal baseline ECG. *D. Clonidine* - **Clonidine** is an alpha-2 agonist used to manage the physical symptoms of **opioid withdrawal** but is not typically used for long-term maintenance programs. - While it can cause **bradycardia** and hypotension, it does not typically cause the **polymorphic ventricular tachycardia** described in this clinical scenario.

Q: Which of the following drugs can be administered through all routes?

Fentanyl. **Explanation:** **Fentanyl** is the correct answer because it is a highly lipophilic opioid with high potency, allowing it to be formulated for virtually every route of administration. Its pharmacological profile supports: * **Parenteral:** IV, IM, and Epidural/Intrathecal (common in anesthesia). * **Transdermal:** Patches for chronic pain management. * **Transmucosal:** Buccal tablets, lozenges ("lollipop"), and sublingual sprays. * **Intranasal:** Used for breakthrough pain. * **Nebulization:** Occasionally used for dyspnea in palliative care. **Why the other options are incorrect:** * **Paracetamol:** While available as Oral, Rectal, and IV (Parven), it is **not** administered via transdermal or inhalational routes due to its chemical properties and the high dosage required for efficacy. * **Penicillin G:** It is acid-labile and destroyed by gastric acid, making it unsuitable for the **oral** route (unlike Penicillin V). It is primarily given IM or IV. * **Azithromycin:** It is available via Oral and IV routes. However, it lacks transdermal, sublingual, or routine inhalational formulations. **NEET-PG High-Yield Pearls:** * **Lipophilicity:** Fentanyl is 100 times more potent than morphine; its high lipid solubility is the key reason it can cross the skin (transdermal) and mucous membranes easily. * **First-Pass Metabolism:** Fentanyl undergoes extensive hepatic first-pass metabolism, which is why the oral (swallowed) route is ineffective, necessitating transmucosal (buccal/sublingual) delivery to bypass the liver. * **Context-Sensitive Half-Life:** Fentanyl’s duration of action increases significantly with prolonged infusions, a critical concept in ICU sedation.

Q: Therapeutic drug monitoring is done for all of the following drugs except?

Diclofenac. **Explanation:** Therapeutic Drug Monitoring (TDM) is the clinical practice of measuring drug concentrations in the blood to maintain a constant concentration within a specific **therapeutic window**. It is indicated for drugs with a narrow therapeutic index, high inter-individual pharmacokinetic variability, or a direct correlation between plasma levels and clinical effects/toxicity. **Why Diclofenac is the correct answer:** Diclofenac is a Non-Steroidal Anti-Inflammatory Drug (NSAID) with a **wide therapeutic index**. Its clinical effect (analgesia and anti-inflammatory action) can be easily monitored by clinical response (reduction in pain or swelling). Furthermore, there is no established correlation between its plasma concentration and its efficacy or toxicity profile, making TDM unnecessary and impractical. **Analysis of incorrect options:** * **Phenytoin:** An antiepileptic with **zero-order (saturated) kinetics** at therapeutic doses. Small dose increases can lead to disproportionately large increases in plasma levels, causing toxicity (e.g., ataxia, nystagmus). TDM is mandatory. * **Tacrolimus & Cyclosporine:** Both are **calcineurin inhibitors** (immunosuppressants) used in organ transplants. They have a very narrow therapeutic window; low levels lead to graft rejection, while high levels cause significant nephrotoxicity and neurotoxicity. TDM is standard of care for these agents. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for TDM drugs:** "**L**ithium, **I**mmunosuppressants (Cyclosporine/Tacrolimus), **T**ricyclic Antidepressants, **A**nti-epileptics (Phenytoin/Valproate), **D**igoxin, **A**minoglycosides, **T**heophylline" (**LITA DAT**). * **Drugs NOT requiring TDM:** Drugs with easily measurable physiological markers (e.g., Warfarin via PT/INR, Antihypertensives via Blood Pressure, Insulin via Blood Glucose). * **Phenytoin** is a classic "TDM favorite" in exams due to its non-linear pharmacokinetics.

Q: Which of the following is an example of physiological antagonism?

Prostacycline–Thromboxane. ### Explanation **Physiological (Functional) Antagonism** occurs when two drugs act on **different receptors** or through different mechanisms, but produce **opposing physiological effects** on the same biological system. **1. Why Option B is Correct:** * **Prostacyclin (PGI2)** acts on IP receptors to cause vasodilation and inhibition of platelet aggregation. * **Thromboxane A2 (TXA2)** acts on TP receptors to cause vasoconstriction and promotion of platelet aggregation. * Since they produce opposite effects using distinct pathways/receptors, they are classic examples of physiological antagonists. **2. Analysis of Incorrect Options:** * **A. Heparin–Protamine:** This is an example of **Chemical Antagonism**. Protamine (strongly basic) reacts chemically with Heparin (strongly acidic) to form an inactive complex, neutralizing its effect without involving receptors. * **C. Adrenaline–Phenoxybenzamine:** This is **Pharmacological Antagonism**. Phenoxybenzamine is a non-competitive antagonist that binds to the same alpha-receptors that Adrenaline targets. * **D. Physostigmine–Acetylcholine:** This is **Synergism/Potentiation**. Physostigmine inhibits the enzyme acetylcholinesterase, preventing the breakdown of Acetylcholine, thereby increasing its concentration and effect. **3. NEET-PG High-Yield Pearls:** * **Most Common Example:** The most frequently asked example of physiological antagonism is **Adrenaline vs. Histamine** on bronchial smooth muscle (Adrenaline causes bronchodilation via $\beta_2$ receptors; Histamine causes bronchoconstriction via $H_1$ receptors). * **Glucagon vs. Insulin:** Another high-yield example (Glucagon increases blood sugar; Insulin decreases it). * **Key Distinction:** Unlike competitive antagonism, physiological antagonism cannot be completely overcome by increasing the dose of the agonist because the drugs work on entirely different systems.

Q: Which drug schedule requires medical supervision for its administration?

Schedule G. The correct answer is **Schedule G**. In the context of the Drugs and Cosmetics Act (1940), different schedules categorize drugs based on their storage, sale, and administration requirements [1, 2]. **Why Schedule G is correct:** Schedule G contains a list of drugs that are mostly used for chronic conditions and require **medical supervision** during their administration. These drugs are not necessarily "dangerous" in the same way as narcotics, but they carry risks that necessitate monitoring by a physician. Labels for these drugs must carry the mandatory warning: "Caution: It is dangerous to take this preparation except under medical supervision." Common examples include Metformin, Glibenclamide, and various antihistamines. **Analysis of Incorrect Options:** * **Schedule H:** These are **Prescription Drugs**. They can only be sold by retail on the prescription of a Registered Medical Practitioner (RMP) [1, 2]. While they require a prescription, they do not specifically mandate "medical supervision" during the actual course of administration. * **Schedule M:** This relates to **Good Manufacturing Practices (GMP)**. It outlines the requirements for factory premises, waste disposal, and equipment for pharmaceutical companies. * **Schedule P:** This specifies the **Life period (expiry date)** and storage conditions for various drugs. **High-Yield Clinical Pearls for NEET-PG:** * **Schedule X:** Includes Psychotropic drugs and Narcotics (e.g., Ketamine, Amphetamines). These require a double-copy prescription, and the pharmacist must preserve the prescription for 2 years [1, 2]. * **Schedule Y:** Guidelines for **Clinical Trials** and import/manufacture of new drugs. * **Schedule K:** List of drugs exempted from certain provisions of manufacture.

Q: Phase I clinical trials are primarily conducted to assess what aspect of a new drug?

Pharmacokinetic profile. **Explanation:** **Correct Answer: D. Pharmacokinetic profile** Phase I clinical trials represent the first stage of testing a new investigational drug in humans. The primary objective is to establish the **pharmacokinetic (PK) profile**, which includes absorption, distribution, metabolism, and excretion (ADME) parameters [1]. This phase determines how the human body handles the drug, helping researchers establish the initial safety margins and biological effects [3]. **Analysis of Options:** * **A. Safety and tolerability:** While Phase I does assess safety and identifies the Maximum Tolerated Dose (MTD), the fundamental scientific goal in this initial human exposure is to map the PK profile [1], [3]. * **B. Therapeutic efficacy:** This is the primary objective of **Phase II** (Proof of Concept) and **Phase III** (Confirmatory) trials [1]. Phase I is typically conducted on healthy volunteers (except for toxic drugs like anti-cancer agents), where efficacy cannot be measured [1], [3]. * **C. Optimal dosage range:** Determining the definitive therapeutic dose range is the goal of **Phase II** clinical trials [1]. Phase I only identifies the dose-limiting toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Study Population:** Usually 20–80 **healthy volunteers** (Exception: Oncology drugs, where patients are used) [3]. * **Phase 0 (Microdosing):** Conducted before Phase I using sub-therapeutic doses to study PK properties and reduce the risk of toxicity. * **Phase IV:** Post-marketing surveillance to detect rare adverse effects (e.g., Phocomelia with Thalidomide) [2]. * **Success Rate:** Phase I has the highest success rate (~70%) compared to subsequent phases.

Q: Type A (augmented) adverse drug reactions are characterized by all EXCEPT:

Qualitatively abnormal responses to the drug. Adverse drug reactions (ADRs) are primarily classified into two types: **Type A (Augmented)** and **Type B (Bizarre)**. ### Why Option A is the Correct Answer **Qualitatively abnormal responses** are the hallmark of **Type B (Bizarre)** reactions, not Type A. Type B reactions (like penicillin anaphylaxis or idiosyncratic reactions) are unrelated to the drug's known pharmacological action and occur only in susceptible individuals. In contrast, Type A reactions are **qualitatively normal but quantitatively increased** (e.g., excessive bleeding with warfarin) [2]. ### Explanation of Incorrect Options * **Option B (Predictable):** Type A reactions are predictable because they are based on the drug’s primary or secondary pharmacological properties [1]. For example, hypoglycemia is a predictable extension of the effect of insulin [3]. * **Option C (Dose-dependent):** These reactions are directly related to the dose administered. Reducing the dose usually resolves the reaction, which is a key management strategy for Type A ADRs [1], [3]. * **Option D (Common):** Type A reactions account for approximately 80% of all ADRs. Because they are predictable and dose-related, they occur frequently in clinical practice [2]. ### NEET-PG High-Yield Pearls * **Mnemonic for Type A:** **A**ugmented, **A**ccepted (predictable), **A**voidable (by dose adjustment). * **Mnemonic for Type B:** **B**izarre, **B**one-breaking (often severe), **B**elieve it or not (unpredictable). * **Type C (Continuous):** Due to long-term use (e.g., Analgesic nephropathy). * **Type D (Delayed):** Occurs years after treatment (e.g., Teratogenicity or Carcinogenicity). * **Type E (End of use):** Withdrawal symptoms (e.g., Clonidine rebound hypertension).

Q: In which phase of clinical trials is the efficacy of a new drug compared with an existing standard drug?

Phase III. **Explanation:** The primary objective of **Phase III clinical trials** is to confirm the therapeutic benefit and safety of a new drug in a large patient population (usually 1,000–3,000 participants). This phase is characterized by **Comparative Studies**, where the new drug is compared against the current "Gold Standard" (existing treatment) or a placebo. This is essential to establish if the new drug offers any clinical advantage over existing therapies before it receives regulatory approval for marketing. **Analysis of Incorrect Options:** * **Phase I (Safety & Pharmacokinetics):** Conducted on a small group (20–80) of healthy volunteers. The goal is to determine the Maximum Tolerated Dose (MTD), safety profile, and pharmacokinetics, not efficacy. * **Phase II (Therapeutic Exploration):** Conducted on a small group (100–300) of actual patients. It aims to establish the "Proof of Concept," determine the dose-response relationship, and assess initial efficacy. It is usually not a comparative study against standard drugs. * **Phase IV (Post-Marketing Surveillance):** Occurs after the drug is launched in the market. It monitors long-term safety, rare side effects (e.g., Phocomelia with Thalidomide), and effects in special populations. **High-Yield Clinical Pearls for NEET-PG:** * **Phase 0:** Also known as **Microdosing** studies; used to determine human PK parameters using sub-therapeutic doses. * **Phase III:** Often referred to as the **"Pivotal Phase"** because its results determine the New Drug Application (NDA) submission. * **Phase II:** Has the highest failure rate in the drug development process. * **Phase IV:** Important for detecting **Idiosyncratic reactions** and rare adverse events not seen in controlled trials.

Q: Adrenaline, noradrenaline, and dopamine act through which type of receptor?

Seven pass receptor. **Explanation:** The correct answer is **C. Seven pass receptor.** Adrenaline, noradrenaline, and dopamine are catecholamines that act as ligands for **G-Protein Coupled Receptors (GPCRs)**. These receptors are characterized by a single polypeptide chain that traverses the cell membrane **seven times**, which is why they are structurally referred to as **Seven-pass receptors** or **Serpentine receptors**. * **Adrenaline and Noradrenaline** act on adrenergic receptors ($\alpha$ and $\beta$). * **Dopamine** acts on dopaminergic receptors ($D_1$ through $D_5$). All of these are classic examples of GPCRs that utilize second messengers like cAMP or $IP_3/DAG$ to exert their cellular effects. **Why other options are incorrect:** * **A. Two-pass receptor:** This is not a standard classification for major neurotransmitter receptors. * **B. Ligand-gated channel:** Also known as ionotropic receptors (e.g., Nicotinic ACh receptors or GABA-A). These act much faster (milliseconds) than GPCRs by directly opening an ion channel upon binding. * **D. One-pass receptor:** These are typically **Enzyme-linked receptors** (e.g., Insulin or Growth Factor receptors) which have a single transmembrane helical segment and intrinsic or associated kinase activity. **High-Yield Clinical Pearls for NEET-PG:** * **GPCRs** are the largest family of cell-surface receptors and the target of approximately 40-50% of all modern drugs. * **Gq-coupled:** $\alpha_1$, $M_1$, $M_3$ (Increases $IP_3/DAG$). * **Gi-coupled:** $\alpha_2$, $M_2$, $D_2$ (Inhibits Adenylyl Cyclase). * **Gs-coupled:** All $\beta$ receptors, $D_1$ (Stimulates Adenylyl Cyclase). * **Speed of action:** Ionotropic (Fastest) > GPCR (Intermediate) > Enzyme-linked > Nuclear receptors (Slowest).

Question 1

All the following are ligand-gated ion channels EXCEPT:

Accepted Answer

H2 receptor

Answer

5-HT3 receptor

Answer

GABA-A receptor

Answer

Nicotinic receptor

Question 2

A 34-year-old male with opioid dependence enrolled in a maintenance programme presents to the emergency department with palpitations and two witnessed syncopal episodes over the past 24 hours. His only medication was started 6 weeks ago at a community addiction clinic. Baseline ECG on enrolment was normal. The on-call resident records the ECG shown in Image 1. Which drug is most likely responsible for the rhythm disturbance seen?

Accepted Answer

A. Methadone

Answer

B. Buprenorphine

Answer

C. Naltrexone

Answer

D. Clonidine

Question 3

Which of the following drugs can be administered through all routes?

Accepted Answer

Fentanyl

Answer

Paracetamol

Answer

Penicillin G

Answer

Azithromycin

Question 4

Therapeutic drug monitoring is done for all of the following drugs except?

Accepted Answer

Diclofenac

Answer

Phenytoin

Answer

Tacrolimus

Answer

Cyclosporine

Question 5

Which of the following is an example of physiological antagonism?

Accepted Answer

Prostacycline–Thromboxane

Answer

Heparin–Protamine

Answer

Adrenaline–Phenoxybenzamine

Answer

Physostigmine–Acetylcholine

Question 6

Which drug schedule requires medical supervision for its administration?

Accepted Answer

Schedule G

Answer

Schedule H

Answer

Schedule M

Answer

Schedule P

Question 7

Phase I clinical trials are primarily conducted to assess what aspect of a new drug?

Accepted Answer

Pharmacokinetic profile

Answer

Safety and tolerability

Answer

Therapeutic efficacy

Answer

Optimal dosage range

Question 8

Type A (augmented) adverse drug reactions are characterized by all EXCEPT:

Accepted Answer

Qualitatively abnormal responses to the drug

Answer

Predictable from the drug's known pharmacological or toxicological effects

Answer

Generally dose-dependent

Answer

Usually common

Question 9

In which phase of clinical trials is the efficacy of a new drug compared with an existing standard drug?

Accepted Answer

Phase III

Answer

Phase I

Answer

Phase II

Answer

Phase IV

Question 10

Adrenaline, noradrenaline, and dopamine act through which type of receptor?

Accepted Answer

Seven pass receptor

Answer

Two pass receptor

Answer

Ligand-gated channel

Answer

One pass receptor

General Pharmacology — MCQs

General Pharmacology — MCQs

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