Analgesics and Anti-inflammatory Drugs — MCQs

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

Question 261: Which of the following statements about Pentazocine is false?

A. Causes decreased vomiting and constipation compared to morphine.
B. Has a lower risk of addiction than morphine.
C. Has a higher risk of addiction than morphine. (Correct Answer)
D. Acts as an agonist-antagonist.

Explanation: **Explanation:** Pentazocine is a benzomorphan derivative that acts as a **Kappa (κ) opioid receptor agonist** and a **Mu (μ) opioid receptor antagonist/partial agonist**. This unique pharmacological profile dictates its clinical effects and side-effect profile. **Why Option C is the Correct (False) Statement:** Pentazocine has a **lower risk of addiction** compared to morphine. Morphine is a pure Mu-agonist; Mu receptors are primarily responsible for the intense euphoria that leads to high abuse potential. Because Pentazocine antagonizes the Mu receptor and primarily acts through Kappa receptors (which can actually cause dysphoria rather than euphoria), its "street value" and physical dependence liability are significantly lower than morphine. It is classified under Schedule H (India) rather than the stricter NDPS Act regulations applied to morphine. **Analysis of Other Options:** * **Option A:** Pentazocine causes less stimulation of the gastrointestinal tract and the chemoreceptor trigger zone (CTZ) compared to morphine, resulting in **decreased constipation and vomiting**. * **Option B:** As explained above, the addiction potential is lower, making this a true statement. * **Option D:** Pentazocine is the prototype **agonist-antagonist**. It is an agonist at Kappa receptors (analgesia, sedation) and an antagonist/weak agonist at Mu receptors. **High-Yield Clinical Pearls for NEET-PG:** 1. **Ceiling Effect:** Unlike morphine, pentazocine exhibits a "ceiling effect" on respiratory depression. 2. **Psychotomimetic Effects:** High doses can cause hallucinations, anxiety, and nightmares due to Kappa receptor activation. 3. **Hemodynamics:** Pentazocine increases heart rate and blood pressure (sympathetic stimulation). Therefore, it is **contraindicated in Myocardial Infarction (MI)**, where morphine remains the drug of choice. 4. **Withdrawal:** It can precipitate withdrawal symptoms in patients already physically dependent on pure Mu-agonists like morphine or heroin.

Question 262: Which of the following NSAIDs can cause hepatic necrosis if used in overdose?

A. Diclofenac sodium
B. Acetaminophen (Correct Answer)
C. Indomethacin
D. Piroxicam

Explanation: **Explanation:** **Acetaminophen (Paracetamol)** is the correct answer because its toxicity is uniquely characterized by **centrilobular hepatic necrosis**. At therapeutic doses, acetaminophen is primarily metabolized via glucuronidation and sulfation. However, a small fraction is converted by Cytochrome P450 (CYP2E1) into a highly reactive toxic metabolite called **NAPQI** (*N-acetyl-p-benzoquinone imine*). In an overdose, the liver's glutathione stores are depleted, leaving NAPQI free to bind to hepatic cellular proteins, leading to oxidative stress and cell death. **Why the other options are incorrect:** * **Diclofenac sodium:** While it can cause idiosyncratic drug-induced liver injury (DILI) or a transient rise in transaminases, it is not classically associated with dose-dependent hepatic necrosis in the same mechanism as acetaminophen. * **Indomethacin:** This is a potent non-selective COX inhibitor primarily known for significant gastrointestinal toxicity, frontal headaches, and hematological side effects (neutropenia). * **Piroxicam:** An oxicam derivative with a long half-life, it is most notorious for causing a high incidence of gastric ulcers and skin reactions (Stevens-Johnson Syndrome). **High-Yield Clinical Pearls for NEET-PG:** * **Antidote:** **N-acetylcysteine (NAC)** is the specific antidote; it acts by replenishing glutathione stores and acting as a glutathione substitute. * **Rumack-Matthew Nomogram:** Used to predict hepatotoxicity risk based on plasma acetaminophen levels relative to the time of ingestion. * **Chronic Alcoholics:** They are at higher risk of toxicity even at lower doses because alcohol induces **CYP2E1**, leading to increased production of NAPQI. * **Toxicity Marker:** The earliest laboratory sign of liver damage in overdose is usually an elevation in **ALT/AST**, followed by an increased Prothrombin Time (PT/INR).

Question 263: Regarding COX-2, which of the following is its function?

A. Cell adhesion
B. Cell proliferation (Correct Answer)
C. Cell migration
D. Cell differentiation

Explanation: Cyclooxygenase-2 (COX-2) is an inducible enzyme primarily expressed during inflammation, injury, or stress [1, 3]. Unlike COX-1, which is "constitutive" and maintains physiological functions (like gastric protection), COX-2 is associated with pathological states, including carcinogenesis [3, 4]. **Why Cell Proliferation is correct:** COX-2 plays a critical role in **cell proliferation** and the inhibition of apoptosis [2]. It catalyzes the synthesis of Prostaglandin E2 (PGE2), which activates signaling pathways (like the Wnt/β-catenin and MAPK pathways) that drive the cell cycle forward. Overexpression of COX-2 is frequently observed in various cancers, most notably **Colorectal Carcinoma** [3]. By promoting proliferation and angiogenesis while suppressing programmed cell death, COX-2 facilitates tumor growth [2]. **Analysis of Incorrect Options:** * **A, C, & D (Cell adhesion, migration, and differentiation):** While COX-2 can indirectly influence the tumor microenvironment (e.g., promoting metastasis via matrix metalloproteinases), its primary, direct enzymatic hallmark in the context of molecular pharmacology and pathology is the stimulation of **proliferation** [2]. Adhesion and differentiation are more closely regulated by integrins and specific transcription factors rather than the prostaglandin pathway. **High-Yield Clinical Pearls for NEET-PG:** * **Selective COX-2 Inhibitors (Celecoxib, Etoricoxib):** These drugs are preferred in patients with peptic ulcers because they spare the protective COX-1 in the stomach. * **Cardiovascular Risk:** COX-2 inhibitors increase the risk of MI and stroke because they inhibit PGI2 (vasodilator/anti-aggregatory) without affecting Thromboxane A2 (vasoconstrictor/pro-aggregatory) produced by COX-1. * **Cancer Prevention:** Regular use of Aspirin or NSAIDs is known to reduce the risk of colorectal polyps and cancer due to the inhibition of COX-2-mediated cell proliferation [3].

Question 264: Which of the following drugs does NOT have an anti-inflammatory effect?

A. Ibuprofen
B. Paracetamol (Correct Answer)
C. Diclofenac
D. Aspirin

Explanation: **Explanation:** The correct answer is **Paracetamol (Acetaminophen)**. While it is a potent analgesic and antipyretic, it lacks significant anti-inflammatory activity at therapeutic doses. **Why Paracetamol is the correct answer:** The primary mechanism of Paracetamol involves the inhibition of prostaglandin synthesis in the **Central Nervous System (CNS)**. However, it is a weak inhibitor of Cyclooxygenase (COX) in peripheral tissues. This is because Paracetamol is inactivated by **peroxides** produced at sites of inflammation. Since inflammation is a peroxide-rich environment, Paracetamol cannot effectively inhibit COX-1 or COX-2 peripherally, thus failing to exert an anti-inflammatory effect. **Why the other options are incorrect:** * **A. Ibuprofen:** A propionic acid derivative and non-selective COX inhibitor. It effectively reduces prostaglandin synthesis both centrally and peripherally, providing significant anti-inflammatory action. * **C. Diclofenac:** A potent phenylacetic acid derivative that inhibits COX-1 and COX-2. It is widely used for its strong anti-inflammatory properties in conditions like osteoarthritis and rheumatoid arthritis. * **D. Aspirin:** An irreversible inhibitor of COX enzymes. At higher doses, it is a classic anti-inflammatory agent used in rheumatic fever and Kawasaki disease. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Paracetamol is the preferred analgesic/antipyretic in children (to avoid **Reye’s Syndrome** associated with Aspirin) and in patients with peptic ulcers or bleeding disorders. * **Toxicity:** Overdose leads to **Centrilobular Hepatic Necrosis** due to the metabolite **NAPQI**. The antidote is **N-acetylcysteine (NAC)**, which replenishes glutathione stores. * **COX-3:** Some literature suggests Paracetamol may act on a splice variant of COX-1, often referred to as COX-3, primarily located in the cerebral cortex.

Question 265: Which NSAID lacks anti-inflammatory action?

A. Paracetamol (Correct Answer)
B. Ibuprofen
C. Diclofenac sodium
D. Celecoxib

Explanation: **Explanation:** The correct answer is **Paracetamol (Acetaminophen)**. **Why Paracetamol is the correct answer:** While Paracetamol is chemically classified as a non-steroidal drug with analgesic and antipyretic properties, it lacks significant **anti-inflammatory** activity. Its mechanism involves the inhibition of prostaglandin synthesis primarily in the **Central Nervous System (CNS)**. In peripheral tissues, its action is neutralized by **peroxides** produced at sites of inflammation. Since it does not effectively inhibit COX enzymes in the periphery, it cannot reduce tissue inflammation. **Why the other options are incorrect:** * **Ibuprofen & Diclofenac sodium:** These are traditional non-selective NSAIDs that inhibit both COX-1 and COX-2 enzymes in both the CNS and peripheral tissues. They are highly effective at reducing prostaglandin-mediated inflammation. * **Celecoxib:** This is a selective COX-2 inhibitor. Since COX-2 is the primary enzyme induced during the inflammatory response, Celecoxib possesses potent anti-inflammatory properties while minimizing GI side effects. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Paracetamol is the preferred analgesic/antipyretic in children (to avoid Reye’s syndrome associated with Aspirin) and in patients with peptic ulcers or bleeding disorders. * **Toxicity:** The toxic metabolite of Paracetamol is **NAPQI**. In overdose, it causes hepatic necrosis. * **Antidote:** **N-acetylcysteine (NAC)**, which replenishes glutathione stores. * **Phenacetin:** Paracetamol is the active metabolite of Phenacetin (withdrawn due to nephrotoxicity).

Question 266: Corticosteroids inhibit _______ to decrease the synthesis of prostaglandins?

A. Phospholipase - C
B. Lipoxygenase
C. Phospholipase - A2 (Correct Answer)
D. Cyclo-oxygenase

Explanation: ### Explanation **Correct Option: C. Phospholipase - A2** **Mechanism of Action:** Corticosteroids exert their anti-inflammatory effects primarily by inducing the synthesis of a group of proteins called **Annexins** (specifically **Lipocortin-1**). Lipocortin directly inhibits the enzyme **Phospholipase A2 (PLA2)**. In the arachidonic acid cascade, PLA2 is the rate-limiting enzyme responsible for releasing arachidonic acid from membrane phospholipids. By inhibiting PLA2, corticosteroids block the production of *all* downstream eicosanoids, including both **prostaglandins** (via the COX pathway) and **leukotrienes** (via the LOX pathway). This broad-spectrum inhibition is why steroids are more potent anti-inflammatory agents than NSAIDs. **Analysis of Incorrect Options:** * **A. Phospholipase - C:** This enzyme is involved in the G-protein coupled receptor (GPCR) signaling pathway, converting PIP2 into IP3 and DAG. It is not the target for corticosteroid-mediated prostaglandin inhibition. * **B. Lipoxygenase (LOX):** While corticosteroids do decrease leukotriene synthesis, they do so by depriving the LOX enzyme of its substrate (arachidonic acid) via PLA2 inhibition, rather than inhibiting the LOX enzyme directly. * **D. Cyclo-oxygenase (COX):** This is the primary target of **NSAIDs** (like Aspirin or Ibuprofen). While corticosteroids can decrease the expression of COX-2 (the inducible form), their fundamental upstream site of action is Phospholipase A2. **High-Yield Clinical Pearls for NEET-PG:** * **Rate-limiting step:** The release of arachidonic acid by PLA2 is the rate-limiting step in eicosanoid synthesis. * **Genomic vs. Non-genomic:** Steroids act via intracellular receptors to alter gene transcription (genomic effect), which explains the lag time in their clinical onset. * **Dual Inhibition:** Unlike NSAIDs, corticosteroids inhibit both the COX and LOX pathways, making them effective in conditions like asthma where leukotrienes play a major role.

Question 267: The mu (u) opioid receptor is responsible for which of the following effects, except?

A. miosis
B. bradycardia
C. hypothermia
D. bronchodilation (Correct Answer)

Explanation: **Explanation:** The **mu (μ) opioid receptor** is the primary mediator for most of the clinical and adverse effects of opioid analgesics (like Morphine). **Why "Bronchodilation" is the correct answer:** Opioids do **not** cause bronchodilation. In fact, they can cause **bronchoconstriction**. This occurs through two mechanisms: 1. **Central Respiratory Depression:** Mu receptors in the brainstem decrease the sensitivity of the respiratory center to CO2. 2. **Histamine Release:** Certain opioids (especially Morphine) trigger mast cell degranulation, leading to histamine release, which causes bronchospasm. Therefore, opioids should be used with caution in patients with bronchial asthma. **Analysis of Incorrect Options:** * **Miosis (A):** Mu and Kappa receptors stimulate the **Edinger-Westphal nucleus** (oculomotor nerve), leading to pupillary constriction (pinpoint pupils). This is a classic sign of opioid overdose. * **Bradycardia (B):** Opioids generally cause vagal stimulation and have a depressant effect on the sinoatrial (SA) node, leading to a decrease in heart rate. * **Hypothermia (C):** Mu receptor activation interferes with the hypothalamic thermoregulatory mechanisms, typically leading to a decrease in body temperature (though effects can vary with dosage and species). **High-Yield Clinical Pearls for NEET-PG:** * **Miosis & Constipation:** These are the two effects of opioids to which **tolerance never develops**. * **Triad of Opioid Overdose:** Coma, Pinpoint pupil, and Respiratory depression. * **Antidote:** **Naloxone** is the drug of choice for acute opioid poisoning (competitive antagonist at all opioid receptors). * **Exception:** Pethidine (Meperidine) is an opioid that causes **mydriasis** (due to its atropine-like action) rather than miosis.

Question 268: Aspirin produces all of the following effects except?

A. Frank gastric bleeding
B. Prolonged prothrombin time
C. Platelet dysfunction
D. Constipation (Correct Answer)

Explanation: **Explanation:** Aspirin (Acetylsalicylic acid) is a non-selective, irreversible inhibitor of Cyclooxygenase (COX-1 and COX-2) enzymes. The correct answer is **Constipation**, as Aspirin and other NSAIDs are more commonly associated with **diarrhea** or dyspepsia rather than constipation (which is a classic side effect of Opioid analgesics). **Why the other options are incorrect:** * **Frank gastric bleeding:** Aspirin inhibits COX-1, which is responsible for synthesizing protective prostaglandins ($PGE_2$ and $PGI_2$) in the gastric mucosa. Loss of these prostaglandins leads to increased acid secretion, reduced mucus production, and direct mucosal irritation, resulting in erosive gastritis and frank GI bleeding. * **Prolonged prothrombin time:** In high doses, Aspirin interferes with the synthesis of clotting factors (specifically Vitamin K-dependent factors) in the liver, leading to a functional hypoprothrombinemia and a prolonged Prothrombin Time (PT). * **Platelet dysfunction:** Aspirin irreversibly acetylates platelet COX-1, inhibiting the production of **Thromboxane $A_2$ ($TXA_2$)**, a potent platelet aggregator. Since platelets cannot synthesize new enzymes, this effect lasts for the entire lifespan of the platelet (approx. 7–10 days). **High-Yield Clinical Pearls for NEET-PG:** * **Zero-order kinetics:** Aspirin follows first-order kinetics at low doses but shifts to zero-order (saturation) kinetics at anti-inflammatory/toxic doses. * **Reye’s Syndrome:** Aspirin is contraindicated in children with viral infections (Flu/Varicella) due to the risk of fulminant hepatic failure and encephalopathy. * **Aspirin Triad (Samter’s Triad):** Asthma, Nasal polyposis, and Aspirin hypersensitivity. * **Toxicity:** Salicylism presents with **Tinnitus** (earliest sign), respiratory alkalosis, and metabolic acidosis. Management involves urinary alkalinization with Sodium Bicarbonate.

Question 269: Which of the following actions of aspirin is manifested at the lowest dose?

A. Analgesic
B. Antipyretic
C. Anti-inflammatory
D. Antiplatelet aggregatory (Correct Answer)

Explanation: ### Explanation Aspirin (Acetylsalicylic acid) exhibits **dose-dependent pharmacological effects** due to its irreversible inhibition of the cyclooxygenase (COX) enzyme. **1. Why Antiplatelet aggregatory is correct:** Aspirin inhibits platelet aggregation at the **lowest doses (75–150 mg/day)**. At this "baby aspirin" dose, it irreversibly acetylates COX-1 in platelets, preventing the synthesis of **Thromboxane A2 (TXA2)**, a potent vasoconstrictor and platelet aggregator. Since platelets lack a nucleus, they cannot synthesize new enzymes, meaning the effect lasts for the entire lifespan of the platelet (8–11 days). **2. Why the other options are incorrect:** * **Analgesic and Antipyretic (Intermediate doses):** These effects require higher doses, typically **300–600 mg** every 4–6 hours. At this level, aspirin inhibits prostaglandin synthesis (PGE2) in the periphery (for pain) and the hypothalamus (for fever). * **Anti-inflammatory (High doses):** This requires the highest therapeutic doses, usually **3–6 grams/day**. At these levels, it significantly inhibits COX-2 and other inflammatory mediators. Such high doses are rarely used now due to the risk of **Salicylism** (tinnitus, vertigo). **3. High-Yield Clinical Pearls for NEET-PG:** * **Zero-order kinetics:** Aspirin follows first-order kinetics at low doses but shifts to **zero-order kinetics** at high/toxic doses due to saturation of metabolic pathways (glycine and glucuronide conjugation). * **Uric Acid excretion:** Aspirin has a paradoxical effect on uric acid. **Low doses (<2g/day)** cause urate retention (hyperuricemia), while **high doses (>5g/day)** are uricosuric. * **Reye’s Syndrome:** Aspirin is contraindicated in children with viral infections (influenza/varicella) due to the risk of hepatic encephalopathy and fatty liver. * **Aspirin Sensitivity:** In patients with "Aspirin-Exacerbated Respiratory Disease" (Samter’s Triad), inhibiting COX shunts arachidonic acid toward the lipoxygenase (LOX) pathway, increasing **leukotrienes** and causing bronchospasm.

Question 270: Which of the following drugs does not possess any agonist action?

A. Buprenorphine
B. Butorphanol
C. Nalbuphine
D. Nalmefene (Correct Answer)

Explanation: ### Explanation The question tests the classification of opioid ligands based on their receptor activity. Opioids are categorized as pure agonists, mixed agonist-antagonists, or pure antagonists. **1. Why Nalmefene is the correct answer:** Nalmefene is a **pure opioid antagonist**. It is a derivative of naltrexone and acts as a competitive antagonist at $\mu$ (mu) and $\delta$ (delta) receptors, and a partial antagonist at $\kappa$ (kappa) receptors. Unlike the other options, it possesses **zero intrinsic activity** (no agonist action) at any opioid receptor. It is primarily used for treating alcohol dependence and opioid overdose due to its longer half-life compared to naloxone. **2. Why the other options are incorrect:** * **Buprenorphine:** It is a **partial $\mu$-agonist** and a $\kappa$-antagonist. Because it has partial agonist activity, it can precipitate withdrawal in opioid-dependent individuals but provides analgesia on its own. * **Butorphanol:** It is a **$\kappa$-agonist** and a $\mu$-antagonist (or partial agonist). Its primary analgesic effect is mediated through kappa receptors. * **Nalbuphine:** Similar to butorphanol, it acts as a **strong $\kappa$-agonist** and a $\mu$-antagonist. It is often used for obstetric analgesia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Pure Antagonists:** Naloxone (IV, short-acting), Naltrexone (Oral, long-acting), and Nalmefene (IV/Oral, longest-acting). * **Buprenorphine** exhibits a "ceiling effect" for respiratory depression, making it safer in overdose, and is used in opioid substitution therapy. * **Mixed Agonist-Antagonists** (Butorphanol, Nalbuphine, Pentazocine) can precipitate withdrawal symptoms if administered to a patient already on a pure $\mu$-agonist like Morphine. * **Naloxone** is the drug of choice for acute opioid poisoning.

Practice by Chapter

NSAIDs: Classification and Mechanism

Practice Questions

COX-2 Selective Inhibitors

Practice Questions

Acetaminophen (Paracetamol)

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Opioid Analgesics and Antagonists

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Drugs Used in Gout and Hyperuricemia

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Drugs Used in Rheumatoid Arthritis

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Disease-Modifying Antirheumatic Drugs

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Glucocorticoids as Anti-inflammatory Agents

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Migraine Therapeutics

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Neuropathic Pain Management

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