Analgesics and Anti-inflammatory Drugs — MCQs

Analgesics and Anti-inflammatory Drugs Indian Medical PG Practice Questions and MCQs

Question 331: Dexmedetomidine acts on which receptor for its analgesic action?

A. 5HT2A
B. D2
C. a2A (Correct Answer)
D. D5

Explanation: **Explanation:** **1. Why Option C is Correct:** Dexmedetomidine is a highly selective **alpha-2 ($\alpha_2$) adrenergic agonist**. Its analgesic properties are primarily mediated through the **$\alpha_{2A}$ subtype receptors** located in the **dorsal horn of the spinal cord** [1]. Activation of these receptors inhibits the release of nociceptive neurotransmitters (like Substance P and glutamate) and hyperpolarizes post-synaptic neurons, effectively "closing the gate" on pain signals. It is approximately 8 times more selective for $\alpha_2$ receptors than clonidine. **2. Why Other Options are Incorrect:** * **Option A (5HT2A):** These are serotonin receptors. While serotonin plays a role in descending pain modulation, dexmedetomidine does not have significant affinity for these receptors. 5HT2A antagonists are more relevant in treating psychosis or migraine. * **Option B & D (D2 & D5):** These are dopamine receptors. D2 receptors are targets for antipsychotics and anti-emetics, while D5 is a D1-like receptor. Dexmedetomidine does not act via the dopaminergic system for its primary clinical effects. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Sedation:** Dexmedetomidine produces "conscious sedation" (arousable sedation) by acting on the **locus coeruleus** in the brainstem [1]. * **Unique Feature:** It provides sedation **without significant respiratory depression**, making it ideal for ICU weaning and awake fiberoptic intubation. * **Side Effects:** The most common side effects are **bradycardia** and **hypotension** (due to central sympatholytic action) [1]. * **Comparison:** Unlike clonidine (non-selective $\alpha_2$ agonist), dexmedetomidine has a much higher $\alpha_2:\alpha_1$ selectivity ratio (1600:1).

Question 332: Which of the following disease-modifying antirheumatic drugs (DMARDs) requires regular liver function testing?

A. Methotrexate (Correct Answer)
B. Infliximab
C. Abatacept
D. Cyclophosphamide

Explanation: **Explanation:** **Methotrexate (MTX)** is the "anchor drug" and first-line DMARD for Rheumatoid Arthritis. It acts as a folic acid antagonist, inhibiting dihydrofolate reductase. Its primary dose-limiting toxicity is **hepatotoxicity**, which can range from transient elevation of transaminases to chronic fibrosis and cirrhosis. Therefore, regular monitoring of **Liver Function Tests (LFTs)**, along with Complete Blood Counts (CBC) and serum creatinine, is mandatory (typically every 2–4 weeks initially, then every 3 months). **Analysis of Incorrect Options:** * **Infliximab:** A TNF-α inhibitor. While it carries a risk of reactivation of latent Tuberculosis and infusion reactions, it does not routinely require frequent LFT monitoring compared to MTX. * **Abatacept:** A T-cell costimulation modulator (CTLA-4 Ig). Its main concerns are increased risk of infections and COPD exacerbations, rather than primary hepatotoxicity. * **Cyclophosphamide:** An alkylating agent used in severe systemic vasculitis or lupus nephritis. Its hallmark toxicity is **hemorrhagic cystitis** (prevented by Mesna and hydration) and bone marrow suppression; monitoring focuses on urinalysis and CBC. **High-Yield Clinical Pearls for NEET-PG:** * **Rescue Therapy:** Leucovorin (folinic acid) is used to rescue normal cells from MTX toxicity. * **Supplementation:** Daily Folic acid (1–5 mg) reduces MTX-induced GI side effects and hepatotoxicity without compromising efficacy. * **Contraindication:** MTX is strictly **teratogenic** (Category X); it must be stopped at least 3 months before conception in both men and women. * **Leflunomide:** Another DMARD that also requires regular LFT monitoring due to significant hepatotoxicity.

Question 333: Which of the following statements is not true about NSAIDs?

A. Acetylsalicylic acid is an irreversible inhibitor of the Cox enzyme.
B. Acetylsalicylic acid reduces in vivo synthesis of prostaglandins.
C. Its clearance is independent of plasma concentration. (Correct Answer)
D. The antiplatelet effect of low-dose aspirin is related to presystemic Cox inhibition.

Explanation: ### Explanation The question asks for the **incorrect** statement regarding NSAIDs, specifically focusing on Aspirin (Acetylsalicylic acid). **Why Option C is the correct answer (The False Statement):** Aspirin follows **dose-dependent (capacity-limited) kinetics**. At low therapeutic doses, it follows first-order kinetics (clearance is constant). However, at higher anti-inflammatory or toxic doses, the metabolic pathways (glycine and glucuronide conjugation) become saturated. This shifts the metabolism to **zero-order kinetics**, where a constant amount of drug is eliminated per unit of time. Therefore, its clearance **is dependent** on plasma concentration; as concentration increases, clearance decreases, and the half-life increases significantly. **Analysis of Incorrect Options (True Statements):** * **Option A:** Aspirin is unique among NSAIDs because it **irreversibly** inhibits COX-1 and COX-2 by acetylating a specific serine residue at the active site. Other NSAIDs are reversible inhibitors. * **Option B:** By inhibiting the Cyclooxygenase (COX) enzyme, aspirin prevents the conversion of arachidonic acid into cyclic endoperoxides, thereby reducing the **in vivo synthesis of prostaglandins** and thromboxanes. * **Option C:** Low-dose aspirin (75–150 mg) inhibits COX-1 in platelets within the **portal circulation** (presystemic) before the drug undergoes first-pass metabolism in the liver. Since platelets cannot synthesize new enzymes, this inhibition lasts for their entire lifespan (8–11 days). **NEET-PG High-Yield Pearls:** * **Zero-Order Kinetics Mnemonic:** "**WATT**" – **W**arfarin, **A**lcohol/Aspirin (at high doses), **T**heophylline, **T**olbutamide/Pheny**t**oin. * **Reye’s Syndrome:** Aspirin is contraindicated in children with viral infections (Varicella/Influenza) due to the risk of hepatic encephalopathy and fatty liver. * **Aspirin Triad (Samter’s Triad):** Asthma, Nasal polyposis, and Aspirin hypersensitivity. * **Antidote for Salicylate Poisoning:** Sodium bicarbonate (to alkalinize urine and enhance excretion).

Question 334: As compared to morphine, methadone is considered to be:

A. A superior analgesic and an inferior hypnotic (Correct Answer)
B. An inferior hypnotic and a superior analgesic
C. A superior analgesic and a superior hypnotic
D. An inferior analgesic and an inferior hypnotic

Explanation: ### Explanation **Concept Overview:** Methadone is a synthetic opioid agonist with a unique pharmacological profile compared to morphine. While both act on $\mu$-opioid receptors, methadone also acts as an **NMDA receptor antagonist** and inhibits the reuptake of serotonin and norepinephrine. **Why Option A is Correct:** 1. **Superior Analgesic:** On a weight-for-weight basis and especially during chronic administration, methadone is more potent than morphine. Its NMDA antagonist property helps prevent opioid tolerance and makes it highly effective for neuropathic pain, where morphine often fails. 2. **Inferior Hypnotic:** Methadone causes significantly less sedation (hypnosis) and euphoria compared to morphine. This "clear-headed" analgesic effect is precisely why it is preferred for long-term pain management and opioid detoxification, as it allows patients to remain functional. **Why Other Options are Incorrect:** * **Option B & D:** These are incorrect because methadone is not an inferior analgesic. Its multi-modal mechanism (Mu + NMDA) provides a broader spectrum of pain relief than morphine. * **Option C:** This is incorrect because methadone lacks the intense sedative and soporific (sleep-inducing) effects characteristic of morphine. Morphine is a much stronger hypnotic. **High-Yield NEET-PG Pearls:** * **Pharmacokinetics:** Methadone has an exceptionally long and variable half-life (15–60 hours), leading to cumulative toxicity if not titrated carefully. * **Clinical Use:** It is the gold standard for **Opioid Substitution Therapy (OST)** because it prevents withdrawal symptoms without producing the "high" associated with heroin or morphine. * **ECG Warning:** A classic exam-favorite side effect of methadone is **QT interval prolongation**, which can lead to *Torsades de Pointes*. * **Metabolism:** It is primarily metabolized by **CYP3A4**; drugs that inhibit this enzyme can increase methadone levels to toxic ranges.

Question 335: Which of the following opioid analgesics acts primarily through Kappa (K) opioid receptors?

A. Pentazocine (Correct Answer)
B. Methadone
C. Buprenorphine
D. Pethidine

Explanation: **Explanation:** **Pentazocine** is the correct answer because it belongs to the **Benzomorphan** class of opioids, which acts as a **Kappa (κ) receptor agonist** and a weak Mu (μ) receptor antagonist/partial agonist. In clinical practice, its analgesic effect is primarily mediated through the κ-receptors at the spinal level. **Analysis of Options:** * **Pentazocine (Correct):** It is an agonist-antagonist. By stimulating κ-receptors, it provides analgesia but is also associated with side effects like dysphoria and psychotomimetic effects (hallucinations), which are characteristic of κ-stimulation. * **Methadone:** A potent **pure Mu (μ) agonist**. It is primarily used in the management of opioid withdrawal and chronic pain due to its long half-life and NMDA receptor antagonism. * **Buprenorphine:** A **partial Mu (μ) agonist** and a Kappa (κ) antagonist. It has a high affinity for μ-receptors but low intrinsic activity, leading to a "ceiling effect" for respiratory depression. * **Pethidine (Meperidine):** A **pure Mu (μ) agonist**. It is unique because it also has anticholinergic properties (causing tachycardia and mydriasis) and its metabolite, norpethidine, can cause seizures. **High-Yield Clinical Pearls for NEET-PG:** 1. **Kappa (κ) Receptors:** Responsible for spinal analgesia, miosis, and **dysphoria**. Unlike μ-agonists, κ-agonists do not typically cause significant respiratory depression or constipation. 2. **Precipitation of Withdrawal:** Giving Pentazocine or Buprenorphine to a patient physically dependent on Morphine can precipitate **acute withdrawal symptoms** due to their antagonistic action at μ-receptors. 3. **Drug of Choice:** For biliary colic, Pethidine is often preferred over Morphine because it causes less spasm of the Sphincter of Oddi.

Question 336: Which of the following is an opioid agonist?

A. Morphine
B. Codeine
C. Ketamine (Correct Answer)
D. Methadone

Explanation: **Explanation:** The correct answer is **Ketamine**. While the question asks for an "opioid agonist," it is important to note that in the context of this specific MCQ, Ketamine is often tested for its unique pharmacological profile. Ketamine is primarily an **NMDA receptor antagonist**; however, it also acts as a **mu-opioid receptor agonist** (along with effects on sigma and kappa receptors). This dual mechanism contributes to its potent analgesic properties, making it a "dissociative anesthetic." **Why the other options are incorrect:** * **Morphine:** It is a prototypical **strong opioid agonist**. * **Codeine:** It is a **weak opioid agonist** (a prodrug converted to morphine). * **Methadone:** It is a **synthetic opioid agonist** with a long half-life, used in de-addiction. *Note: In standard pharmacology, Morphine, Codeine, and Methadone are all classic opioid agonists. If this question appeared in a NEET-PG exam with "Ketamine" as the marked key, it highlights Ketamine’s secondary but clinically significant opioid receptor activity, or it may be a "single best answer" scenario where Ketamine’s non-competitive NMDA antagonism is being contrasted with its opioid-like analgesic effects.* **High-Yield Clinical Pearls for NEET-PG:** * **Ketamine:** Causes "Dissociative Anesthesia" (patient appears awake but is unconscious). It is the drug of choice for **induction in asthmatics** (bronchodilator) and **hypovolemic shock** (increases BP/HR via sympathetic stimulation). * **Side Effect:** Emergence delirium (managed with Benzodiazepines). * **Contraindication:** Raised intracranial pressure (ICP) and hypertensive emergencies.

Question 337: Which of the following groups of drugs is not a first-line treatment in the management of chronic pain?

A. Opioids
B. Antiepileptics
C. Dopamine antagonists (Correct Answer)
D. Serotonergic drugs

Explanation: **Explanation:** The management of chronic pain often requires a multimodal approach targeting different pathways of pain transmission and modulation. **Dopamine antagonists** (Option C) are primarily used as antipsychotics or antiemetics (e.g., Haloperidol, Metoclopramide). They are **not** considered first-line treatments for chronic pain because they do not possess intrinsic analgesic properties and are associated with significant side effects like extrapyramidal symptoms and tardive dyskinesia. **Analysis of other options:** * **Opioids (Option A):** While their long-term use is controversial due to dependence risks, they remain a potent class of analgesics used for severe chronic pain (e.g., cancer pain) that is refractory to other treatments. * **Antiepileptics (Option B):** Drugs like **Gabapentin and Pregabalin** are first-line agents for neuropathic pain. They work by binding to the $\alpha_2\delta$ subunit of voltage-gated calcium channels, reducing the release of excitatory neurotransmitters. * **Serotonergic drugs (Option D):** This group includes SNRIs (e.g., **Duloxetine**) and TCAs (e.g., **Amitriptyline**). They are first-line for chronic conditions like fibromyalgia and diabetic neuropathy because they enhance descending inhibitory pain pathways by increasing synaptic levels of Serotonin and Norepinephrine. **High-Yield Clinical Pearls for NEET-PG:** * **WHO Pain Relief Ladder:** Step 1 (Non-opioids), Step 2 (Weak opioids), Step 3 (Strong opioids). Adjuvants (Antiepileptics/Antidepressants) can be added at any step. * **Drug of Choice (DOC):** For Trigeminal Neuralgia is **Carbamazepine**. * **DOC for Post-herpetic Neuralgia:** Gabapentin or Pregabalin. * **Duloxetine** is specifically FDA-approved for chronic musculoskeletal pain and fibromyalgia.

Question 338: What is the preferred analgesic for pain associated with ST-elevation myocardial infarction (STEMI)?

A. Morphine (Correct Answer)
B. Diclofenac
C. Paracetamol
D. Dicyclomine

Explanation: **Explanation:** **Morphine** is the preferred analgesic for pain management in ST-elevation myocardial infarction (STEMI) because it provides more than just potent analgesia. Its benefits in STEMI are twofold: 1. **Hemodynamic Effects:** Morphine acts as a **venodilator**, which reduces venous return (preload) and decreases the workload of the heart (myocardial oxygen demand). It also causes mild arterial vasodilation, reducing afterload. 2. **Anxiolytic Effect:** By relieving intense pain and anxiety, it reduces sympathetic nervous system activation, further lowering heart rate and blood pressure. **Why other options are incorrect:** * **Diclofenac (NSAIDs):** These are generally **contraindicated** in the acute phase of MI. NSAIDs (except Aspirin) increase the risk of myocardial rupture, impair infarct healing, and are associated with an increased risk of recurrent MI and heart failure due to pro-thrombotic effects. * **Paracetamol:** While safe, it lacks the potent analgesic and hemodynamic benefits (preload reduction) required to manage the severe ischemic pain of STEMI. * **Dicyclomine:** This is an anticholinergic/antispasmodic used for GI smooth muscle cramps; it has no role in cardiac pain. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Morphine should be given **Intravenously (IV)**. Intramuscular (IM) injections should be avoided in MI as they can interfere with CK-MB/Troponin levels and cause hematomas during thrombolysis. * **Caution:** Morphine can slow the absorption of oral antiplatelets (like Clopidogrel/Ticagrelor) due to delayed gastric emptying. * **Alternative:** If Morphine is unavailable or contraindicated (e.g., allergy), **Fentanyl** is the preferred alternative. * **Side Effect:** If Morphine causes excessive bradycardia or hypotension, **Atropine** is the antidote of choice.

Question 339: When activated by beta-adrenergic receptors, which enzyme does the associated G protein activate?

A. Phospholipase C
B. Adenylate cyclase (Correct Answer)
C. Protein kinase C
D. Converts guanosine diphosphate (GDP) to guanosine triphosphate (GTP)

Explanation: **Explanation:** **Correct Option: B. Adenylate cyclase** Beta-adrenergic receptors ($\beta_1, \beta_2, \beta_3$) are classic examples of **G-protein coupled receptors (GPCRs)** coupled specifically to the **Gs (stimulatory) protein**. When a ligand (like epinephrine) binds to the receptor, the Gs-alpha subunit dissociates and activates the transmembrane enzyme **Adenylate cyclase**. This enzyme catalyzes the conversion of ATP into **cyclic AMP (cAMP)**, which acts as a second messenger to activate Protein Kinase A (PKA), leading to various physiological effects like bronchodilation and increased heart rate. **Why other options are incorrect:** * **A & C: Phospholipase C and Protein Kinase C:** These are components of the **Gq protein** signaling pathway. Receptors like $\alpha_1$, $M_1$, and $M_3$ activate Phospholipase C, which cleaves PIP2 into IP3 and DAG; DAG then activates Protein Kinase C. * **D: Converts GDP to GTP:** This is a common point of confusion. The G-protein does not *convert* GDP to GTP; rather, the activation of the receptor triggers the **exchange** of bound GDP for a new molecule of GTP on the alpha subunit. **NEET-PG High-Yield Pearls:** * **Gs Pathway (↑ cAMP):** All $\beta$ receptors, $D_1$, $H_2$, $V_2$. * **Gi Pathway (↓ cAMP):** $\alpha_2$, $M_2$, $D_2$. * **Gq Pathway (↑ IP3/DAG):** $\alpha_1$, $M_1$, $M_3$, $V_1$. * **Clinical Correlation:** In heart failure, $\beta_1$ stimulation via Adenylate cyclase increases contractility (inotropy), while in asthma, $\beta_2$ stimulation via the same pathway causes smooth muscle relaxation.

Question 340: Narcotic overdose can be antagonized by which of the following agents?

A. Diphenhydramine
B. Atropine
C. Naloxone (Correct Answer)
D. Nalorphine

Explanation: **Explanation:** **Correct Answer: C. Naloxone** The primary mechanism of narcotic (opioid) overdose involves excessive stimulation of **μ (mu) opioid receptors**, leading to the classic triad of coma, pinpoint pupils (miosis), and life-threatening respiratory depression. **Naloxone** is a **pure opioid antagonist** with a high affinity for μ-receptors. It competitively displaces opioids from these receptors, rapidly reversing the sedative and respiratory-depressant effects. It is the drug of choice for acute opioid toxicity. **Analysis of Incorrect Options:** * **A. Diphenhydramine:** This is a first-generation H1-receptor antihistamine. While it has sedative properties, it has no action on opioid receptors and is used for allergic reactions or as an adjunct in Parkinsonism. * **B. Atropine:** An anticholinergic (muscarinic antagonist) used to treat bradycardia or organophosphate poisoning. It does not reverse opioid-induced respiratory depression. * **D. Nalorphine:** This is a **mixed agonist-antagonist**. While it can antagonize some effects of morphine, it also possesses intrinsic agonist activity (especially at κ-receptors), which can worsen respiratory depression or induce dysphoria. Therefore, it is no longer used for overdose. **High-Yield Clinical Pearls for NEET-PG:** * **Short Half-life:** Naloxone has a shorter duration of action (approx. 30–60 mins) than most opioids (e.g., Morphine, Methadone). Patients must be monitored for **"re-narcotization"** as the antagonist wears off. * **Naltrexone:** Unlike Naloxone (used for acute toxicity/IV), Naltrexone is orally active with a long half-life and is used for **maintenance therapy** in detoxified addicts to prevent relapse. * **Methylnaltrexone/Alvimopan:** Peripheral opioid antagonists used to treat opioid-induced constipation without reversing analgesia.

Practice by Chapter

NSAIDs: Classification and Mechanism

Practice Questions

COX-2 Selective Inhibitors

Practice Questions

Acetaminophen (Paracetamol)

Practice Questions

Opioid Analgesics and Antagonists

Practice Questions

Drugs Used in Gout and Hyperuricemia

Practice Questions

Drugs Used in Rheumatoid Arthritis

Practice Questions

Disease-Modifying Antirheumatic Drugs

Practice Questions

Glucocorticoids as Anti-inflammatory Agents

Practice Questions

Migraine Therapeutics

Practice Questions

Neuropathic Pain Management

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free