Question 1

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. ***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. [Practice more Pharmacology questions on OnCourse]

Question 2

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

Accepted Answer

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. [Practice more Pharmacology questions on OnCourse]

Question 3

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

Accepted Answer

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. [Practice more Pharmacology questions on OnCourse]

Question 4

Which of the following is an example of physiological antagonism?

Accepted Answer

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. [Practice more Pharmacology questions on OnCourse]

Question 5

Which drug schedule requires medical supervision for its administration?

Accepted Answer

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. [Practice more Pharmacology questions on OnCourse]

Pharmacology Questions

Topics

General Pharmacology

Autonomic Nervous System Drugs

Cardiovascular Drugs

Diuretics

Drugs Affecting Blood and Blood Formation

Central Nervous System Pharmacology

Analgesics and Anti-inflammatory Drugs

Antimicrobial Agents

Anticancer Drugs

Drugs for Gastrointestinal Diseases

Endocrine Pharmacology

Respiratory System Drugs

Drugs in Psychiatric Disorders

Drugs Used in Skin Disorders

Clinical Pharmacology and Drug Toxicity

Pharmacokinetics and Pharmacodynamics

Drug Interactions

Pharmacogenomics

Pediatric and Geriatric Pharmacology

Emergency Pharmacology

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