Analgesics and Anti-inflammatory Drugs — MCQs

A 45-year-old male presented with severe pain in the knee and shoulder joints. A diagnosis of rheumatoid arthritis was made and the patient was started on methotrexate 15mg weekly. However, even after 6 months of treatment, recurrent episodes of arthritis continued. The physician wanted to add another disease-modifying antirheumatic drug (DMARD) that inhibits pyrimidine synthesis by inhibiting the dihydroorotate dehydrogenase enzyme. Which of the following drugs is the physician considering?

Q47Easy

What is the primary effect of morphine on the chemoreceptor trigger zone (CTZ) of the medulla?

Q48Easy

Which component of sulfasalazine is responsible for the therapeutic effect in rheumatoid arthritis?

Q49Medium

Which of the following analgesic combinations should be avoided?

Q50Easy

Which NSAID is proposed to act by inhibition of COX-3?

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

Question 41: All of the following effects are produced by mu opioid receptor activation, except?

A. Tachycardia (Correct Answer)
B. Miosis
C. Sedation
D. Euphoria

Explanation: **Explanation:** The correct answer is **A. Tachycardia**. Opioids act primarily through three types of G-protein coupled receptors: **Mu (μ)**, **Kappa (κ)**, and **Delta (δ)**. Activation of the Mu receptor (the primary mediator of opioid effects) typically results in **Bradycardia**, not tachycardia. This occurs because opioids increase vagal (parasympathetic) tone and decrease sympathetic outflow from the vasomotor center. **Why other options are incorrect:** * **Miosis (B):** Mu and Kappa receptor activation stimulates the **Edinger-Westphal nucleus** of the oculomotor nerve, leading to pupillary constriction (pinpoint pupils). This is a classic sign of opioid overdose and, unlike many other effects, tolerance does not develop to miosis. * **Sedation (C):** Opioids produce a dose-dependent depression of the Central Nervous System (CNS), leading to drowsiness and mental clouding. * **Euphoria (D):** Mu receptor activation in the ventral tegmental area leads to dopamine release in the nucleus accumbens, producing a powerful sense of well-being and pleasure, which contributes to the high addiction potential of these drugs. **High-Yield Clinical Pearls for NEET-PG:** * **The "Miosis Exception":** Meperidine (Pethidine) is an opioid that causes **mydriasis** (dilation) rather than miosis due to its atropine-like (antimuscarinic) properties. * **Tolerance:** Tolerance develops to most opioid effects *except* **Miosis** and **Constipation**. * **Triad of Opioid Overdose:** Coma, Pinpoint pupils, and Respiratory depression. * **Antidote:** Naloxone is the competitive antagonist used to reverse Mu-receptor-mediated respiratory depression.

Question 42: What process is inhibited by COX-2?

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

Explanation: **Explanation:** Cyclooxygenase-2 (COX-2) is an inducible enzyme primarily expressed during inflammation and neoplasia. While COX-1 is "constitutive" (maintaining homeostatic functions like gastric protection), COX-2 is upregulated by growth factors, cytokines, and tumor promoters. **Why Cell Proliferation is the correct answer:** COX-2 plays a pivotal role in the cell cycle. It catalyzes the synthesis of Prostaglandin E2 (PGE2), which activates signaling pathways (like Wnt/β-catenin and MAPK) that stimulate **cell proliferation** and inhibit apoptosis. Consequently, the inhibition of COX-2 leads to a decrease in cell division. This is the pharmacological basis for using NSAIDs (like Celecoxib or Aspirin) in the chemoprevention of colorectal adenomas and other malignancies where COX-2 is overexpressed. **Analysis of Incorrect Options:** * **A & C (Cell Adhesion and Migration):** While COX-2 can indirectly influence the metastatic potential of cancer cells, its primary and most direct regulatory effect is on the mitotic rate and survival of the cell itself. * **B (Cell Differentiation):** COX-2 activity is generally associated with maintaining an undifferentiated, proliferative state in stem cells and cancer cells. Inhibition usually promotes or restores differentiation rather than inhibiting it. **NEET-PG High-Yield Pearls:** * **Selective COX-2 Inhibitors (Coxibs):** These lack anti-platelet effects (as platelets only express COX-1) but increase cardiovascular risk due to an imbalance between Thromboxane A2 and Prostacyclin (PGI2). * **Clinical Application:** Celecoxib is FDA-approved for reducing the number of polyps in **Familial Adenomatous Polyposis (FAP)**. * **Expression:** COX-2 is constitutively expressed in only a few sites: the **Kidney, Brain, and Spinal Cord.**

Question 43: A 25-year-old woman develops a sore, red, hot, swollen left knee. She has no history of trauma and no familial history of joint disease. Aspirin is effective in relieving symptoms of acute inflammation in this patient because it inhibits which of the following enzymes?

A. Cyclooxygenase (Correct Answer)
B. Myeloperoxidase
C. Phospholipase A2
D. Superoxide dismutase

Explanation: ### Explanation **Correct Option: A. Cyclooxygenase** Aspirin (Acetylsalicylic acid) is a Non-Steroidal Anti-Inflammatory Drug (NSAID) that exerts its anti-inflammatory, analgesic, and antipyretic effects by **irreversibly inhibiting the enzyme Cyclooxygenase (COX-1 and COX-2)**. This inhibition prevents the conversion of arachidonic acid into **prostaglandins (PGs)** and thromboxanes. Prostaglandins (specifically PGE2 and PGI2) are the primary mediators of the cardinal signs of inflammation—vasodilation (redness/heat), increased vascular permeability (swelling), and sensitization of pain receptors (soreness). **Why Incorrect Options are Wrong:** * **B. Myeloperoxidase:** This enzyme is found in neutrophil granules and is involved in the production of hypochlorous acid to kill bacteria; it is not the target of aspirin. * **C. Phospholipase A2:** This enzyme releases arachidonic acid from membrane phospholipids. It is inhibited by **Corticosteroids** (via lipocortin/annexin A1), not by NSAIDs. * **D. Superoxide dismutase:** This is an antioxidant enzyme that neutralizes superoxide radicals; it is not involved in the mechanism of action of common analgesics. **High-Yield NEET-PG Pearls:** * **Irreversible Binding:** Aspirin is unique among NSAIDs because it **acetylates** the serine residue of COX, leading to irreversible inhibition. Other NSAIDs (like Ibuprofen) are reversible inhibitors. * **Antiplatelet Effect:** At low doses (75–150 mg), aspirin selectively inhibits COX-1 in platelets, preventing Thromboxane A2 (TXA2) synthesis for the lifetime of the platelet (8–11 days). * **Zero-Order Kinetics:** At high/toxic doses, aspirin metabolism shifts from first-order to zero-order kinetics. * **Reye’s Syndrome:** Aspirin is contraindicated in children with viral infections (flu/chickenpox) due to the risk of fulminant hepatic failure and encephalopathy.

Question 44: All of the following are TNF alpha inhibitors except?

A. Infliximab
B. Adalimumab
C. Omalizumab (Correct Answer)
D. Etanercept

Explanation: **Explanation:** The question tests your ability to distinguish between different classes of monoclonal antibodies used in immunological disorders. **Why Omalizumab is the correct answer:** **Omalizumab** is a recombinant DNA-derived humanized monoclonal antibody that selectively binds to **free human Immunoglobulin E (IgE)**. By binding to IgE, it prevents the binding of IgE to the high-affinity receptor (FcεRI) on the surface of mast cells and basophils, thereby inhibiting the allergic cascade. It is clinically indicated for **moderate-to-severe persistent asthma** and chronic idiopathic urticaria, not for conditions requiring TNF-α inhibition. **Analysis of Incorrect Options (TNF-α Inhibitors):** * **Infliximab (Option A):** A chimeric monoclonal antibody that binds to both soluble and transmembrane forms of TNF-α. It is widely used in Crohn’s disease and Rheumatoid Arthritis (RA). * **Adalimumab (Option B):** A fully human monoclonal antibody against TNF-α. It has a lower risk of neutralizing antibody formation compared to Infliximab. * **Etanercept (Option D):** A soluble **decoy receptor** (fusion protein) that binds to TNF molecules in the circulation, preventing them from interacting with cell surface receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Screening:** Before starting any TNF-α inhibitor, patients **must be screened for Latent Tuberculosis** (via TST or IGRA) because these drugs can cause reactivation of TB. * **Suffix Clues:** * *-ximab:* Chimeric (e.g., Infliximab) * *-zumab:* Humanized (e.g., Omalizumab) * *-mumab:* Fully Human (e.g., Adalimumab) * *-cept:* Receptor fusion protein (e.g., Etanercept) * **Other TNF Inhibitors:** Certolizumab (pegylated) and Golimumab.

Question 45: Which intra-articular steroid is least preferred in osteoarthritis?

A. Triamcinolone
B. Hydrocortisone
C. Prednisolone (Correct Answer)
D. Betamethasone

Explanation: **Explanation:** The goal of intra-articular (IA) corticosteroid injection in osteoarthritis is to provide localized anti-inflammatory relief with minimal systemic absorption and maximum duration of action within the joint space. **Why Prednisolone is the correct answer:** Prednisolone is a **highly soluble** corticosteroid. In the context of IA injections, high solubility is a disadvantage because the drug is rapidly absorbed into the systemic circulation from the synovial fluid. This results in a very short duration of local therapeutic effect (often less than 24 hours) and an increased risk of systemic side effects. Therefore, it is the least preferred agent for local joint infiltration. **Analysis of Incorrect Options:** * **Triamcinolone (Option A):** This is a **low-solubility ester** (e.g., Triamcinolone acetonide/hexacetonide). Its crystalline formulation allows it to remain in the joint space for several weeks, providing prolonged relief. It is often considered the "gold standard" for IA injections. * **Hydrocortisone (Option B):** While less potent than triamcinolone, it is frequently used in acetate form (insoluble) for smaller joints. However, it is still more appropriate than plain prednisolone due to its formulation. * **Betamethasone (Option C):** Often used as a combination of a soluble (rapid onset) and insoluble (long-acting) ester (e.g., Betamethasone sodium phosphate and acetate), making it highly effective for IA use. **High-Yield Clinical Pearls for NEET-PG:** * **Ideal IA Steroid:** Should be **insoluble/repository** (e.g., Triamcinolone hexacetonide) to ensure long-term local residence. * **Frequency:** IA injections should generally not be administered more than **3–4 times a year** in the same joint to prevent "steroid arthropathy" (cartilage damage). * **Post-injection Flare:** A common side effect where crystals cause temporary joint irritation (distinguish this from septic arthritis). * **Potency:** Dexamethasone and Betamethasone are the most potent, while Hydrocortisone is the least potent.

Question 46: A 45-year-old male presented with severe pain in the knee and shoulder joints. A diagnosis of rheumatoid arthritis was made and the patient was started on methotrexate 15mg weekly. However, even after 6 months of treatment, recurrent episodes of arthritis continued. The physician wanted to add another disease-modifying antirheumatic drug (DMARD) that inhibits pyrimidine synthesis by inhibiting the dihydroorotate dehydrogenase enzyme. Which of the following drugs is the physician considering?

A. Sulfasalazine
B. Infliximab
C. Leflunomide (Correct Answer)
D. Abatacept

Explanation: ### Explanation **Correct Option: C. Leflunomide** **Mechanism of Action:** Leflunomide is a prodrug that is converted into its active metabolite, **A77 1726 (malononitrilamide)**. This metabolite acts as a potent inhibitor of the mitochondrial enzyme **dihydroorotate dehydrogenase (DHODH)**. This enzyme is critical for the **de novo synthesis of pyrimidines** (specifically UMP). Since activated T-lymphocytes require rapid pyrimidine synthesis to proliferate, Leflunomide effectively arrests the cell cycle in the G1 phase, thereby exerting its immunosuppressive effect in Rheumatoid Arthritis. **Analysis of Incorrect Options:** * **A. Sulfasalazine:** It is a DMARD used in RA, but its exact mechanism is unclear. It is thought to inhibit NF-κB and reduce cytokine production, but it does not inhibit pyrimidine synthesis. * **B. Infliximab:** This is a biological DMARD that acts as a **chimeric monoclonal antibody against TNF-α**. It does not interfere with metabolic pathways like pyrimidine synthesis. * **D. Abatacept:** This is a biological agent that inhibits T-cell costimulation by binding to **CD80 and CD86** on antigen-presenting cells, preventing their interaction with CD28 on T-cells. **High-Yield Clinical Pearls for NEET-PG:** * **Loading Dose:** Leflunomide has a very long half-life (approx. 2 weeks); hence, a loading dose is often used to reach steady state quickly. * **Side Effects:** Hepatotoxicity (monitor LFTs) and diarrhea are common. It is also highly **teratogenic**. * **Washout Procedure:** Due to its long half-life, if a patient needs to stop the drug (e.g., for pregnancy), **Cholestyramine** is administered to enhance biliary excretion and "wash out" the drug. * **Comparison:** While Methotrexate inhibits *purine* synthesis (via dihydrofolate reductase), Leflunomide inhibits *pyrimidine* synthesis.

Question 47: What is the primary effect of morphine on the chemoreceptor trigger zone (CTZ) of the medulla?

A. Stimulates the CTZ zone of the medulla (Correct Answer)
B. Stimulates the respiratory center of the medulla
C. Depresses the CTZ zone of the medulla
D. None of the above

Explanation: **Explanation:** **1. Why Option A is Correct:** Morphine and other opioids induce nausea and vomiting primarily by **direct stimulation of the Chemoreceptor Trigger Zone (CTZ)** located in the *area postrema* on the floor of the fourth ventricle [2]. The CTZ is rich in $\mu$ and $\kappa$ opioid receptors. Stimulation of these receptors triggers the vomiting center. Interestingly, while morphine stimulates the CTZ, it simultaneously **depresses the vomiting center** in the medulla. This is why, at higher or repeated doses, morphine may actually exert an anti-emetic effect. **2. Why Other Options are Incorrect:** * **Option B:** Morphine is a potent **respiratory depressant** [1]. It acts directly on the brainstem respiratory centers to reduce their responsiveness to carbon dioxide ($CO_2$) [3]. It does not stimulate the respiratory center; rather, respiratory depression is the most common cause of death in opioid overdose. * **Option C:** As established, the initial effect of morphine on the CTZ is excitatory (stimulation), not inhibitory (depression). Depression occurs at the level of the vomiting center, not the CTZ. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vestibular Component:** Morphine also increases the sensitivity of the vestibular apparatus; hence, opioid-induced nausea is often worse in ambulatory patients than in those lying still [2]. * **Miosis:** Morphine causes "pinpoint pupils" via stimulation of the **Edinger-Westphal nucleus** (oculomotor nerve). This is a classic sign of opioid overdose where tolerance does not develop [1]. * **Biliary Colic:** Morphine causes constriction of the **Sphincter of Oddi**, leading to increased intrabiliary pressure. * **Antidote:** **Naloxone** is the drug of choice for reversing morphine-induced respiratory depression and CTZ stimulation.

Question 48: Which component of sulfasalazine is responsible for the therapeutic effect in rheumatoid arthritis?

A. Intact sulfasalazine molecule
B. Sulfapyridine (Correct Answer)
C. 5-aminosalicylic acid
D. Both sulfapyridine and 5-aminosalicylic acid

Explanation: **Explanation:** Sulfasalazine is a prodrug composed of **Sulfapyridine** and **5-aminosalicylic acid (5-ASA)** linked by a covalent azo bond. This bond is cleaved by bacterial enzymes (azoreductases) in the colon. **1. Why Sulfapyridine is correct:** In **Rheumatoid Arthritis (RA)**, sulfasalazine acts as a Disease-Modifying Antirheumatic Drug (DMARD). The **sulfapyridine** moiety is absorbed systemically from the colon and is responsible for the anti-inflammatory and immunomodulatory effects in the joints. It inhibits the release of inflammatory cytokines (like IL-1 and TNF-α) and may suppress B-cell activity. **2. Why other options are incorrect:** * **5-aminosalicylic acid (5-ASA):** This component remains largely unabsorbed and stays in the colon. It is the active moiety for **Ulcerative Colitis** and Crohn’s disease due to its local anti-inflammatory effect on the bowel mucosa. It has no role in treating systemic joint disease. * **Intact sulfasalazine molecule:** The intact molecule is poorly absorbed from the gut and serves primarily as a vehicle to deliver the two active components to the distal bowel. **High-Yield Clinical Pearls for NEET-PG:** * **Adverse Effects:** Most side effects (nausea, rashes, agranulocytosis, and reversible oligospermia) are attributed to the **sulfapyridine** component. * **Monitoring:** Due to the risk of bone marrow suppression, CBC and LFTs should be monitored. * **Metabolism:** Sulfapyridine is metabolized via **acetylation** in the liver. "Slow acetylators" are at a higher risk of toxicity. * **Safe in Pregnancy:** Sulfasalazine is generally considered one of the safer DMARDs during pregnancy (Category B).

Question 49: Which of the following analgesic combinations should be avoided?

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

Explanation: ### Explanation **Correct Option: D. Ibuprofen and Diclofenac** The combination of **Ibuprofen and Diclofenac** should be avoided because both drugs belong to the same pharmacological class: **Non-Steroidal Anti-inflammatory Drugs (NSAIDs)**. 1. **Mechanism of Action:** Both drugs work by non-selectively inhibiting the enzymes COX-1 and COX-2. 2. **Therapeutic Ceiling Effect:** Combining two NSAIDs does not provide additive analgesic efficacy; instead, it reaches a "ceiling effect" where no further pain relief is achieved. 3. **Increased Toxicity:** The simultaneous use of two NSAIDs significantly increases the risk of serious adverse effects, particularly **gastrointestinal bleeding, peptic ulcers, and nephrotoxicity** (due to synergistic inhibition of protective prostaglandins). --- ### Analysis of Incorrect Options: * **A. Aspirin and Codeine:** This is a rational combination of a peripheral analgesic (NSAID) and a central opioid analgesic. They have different mechanisms of action, providing additive pain relief. * **B. Paracetamol and Dextropropoxyphene:** This combination (often found in formulations like Proxvon) pairs a non-opioid with a mild opioid. While Dextropropoxyphene is being phased out in many regions due to cardiac concerns, the *combination* itself is pharmacologically synergistic. * **C. Ibuprofen and Paracetamol:** This is a very common and effective combination. Paracetamol acts primarily on the CNS (COX-3/POX), while Ibuprofen acts peripherally. They have different safety profiles and are often used together for superior analgesia with lower doses of each. --- ### High-Yield Clinical Pearls for NEET-PG: * **Rule of Thumb:** Never combine two traditional NSAIDs (e.g., Naproxen + Ketorolac) or an NSAID with a Selective COX-2 inhibitor (e.g., Diclofenac + Celecoxib). * **Aspirin Interaction:** If a patient is on low-dose Aspirin for cardioprotection, Ibuprofen should be taken **at least 30 minutes after or 8 hours before** Aspirin, as Ibuprofen can competitively block Aspirin’s binding site on COX-1, neutralizing its antiplatelet effect. * **Drug of Choice:** For closure of Patent Ductus Arteriosus (PDA), the preferred NSAID is **Indomethacin** or **Ibuprofen**.

Question 50: Which NSAID is proposed to act by inhibition of COX-3?

A. Nimesulide
B. Paracetamol (Correct Answer)
C. Ketorolac
D. Rofecoxib

Explanation: **Explanation:** **Correct Answer: B. Paracetamol** Paracetamol (Acetaminophen) is unique among common analgesics because it possesses potent analgesic and antipyretic properties but lacks significant peripheral anti-inflammatory activity. This clinical profile is attributed to its mechanism of action: it primarily inhibits prostaglandin synthesis in the **Central Nervous System (CNS)**. It is proposed that Paracetamol acts by inhibiting **COX-3**, a splice variant of the COX-1 enzyme found predominantly in the cerebral cortex and heart. By inhibiting COX-3, Paracetamol reduces pain and fever without affecting peripheral COX-1 or COX-2, which explains why it does not cause gastric ulcers or anti-platelet effects. **Analysis of Incorrect Options:** * **A. Nimesulide:** A **preferential COX-2 inhibitor**. It is known for its rapid onset of action but is associated with a risk of hepatotoxicity. * **C. Ketorolac:** A **non-selective COX inhibitor** with exceptionally potent analgesic activity. It is primarily used for short-term management of severe acute pain (e.g., post-operative) but has a high risk of GI side effects. * **D. Rofecoxib:** A **selective COX-2 inhibitor**. Most drugs in this class (Coxibs) were withdrawn or restricted due to an increased risk of cardiovascular events (thrombotic strokes and MI). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Paracetamol is the DOC for fever in children (to avoid Reye’s syndrome associated with Aspirin) and during pregnancy. * **Antidote:** In Paracetamol toxicity (NAPQI accumulation), the antidote is **N-acetylcysteine (NAC)**, which replenishes glutathione stores. * **Key Limitation:** Paracetamol is **not** an NSAID in the functional sense because it lacks anti-inflammatory activity at therapeutic doses.

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

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Glucocorticoids as Anti-inflammatory Agents

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Migraine Therapeutics

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Neuropathic Pain Management

Practice Questions

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