COX-2 Selective Inhibitors Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for COX-2 Selective Inhibitors. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
COX-2 Selective Inhibitors Indian Medical PG Question 1: All of the following occurs because of prostaglandin use except?
- A. Increased motility of bowel
- B. Nausea
- C. Excess water retention (Correct Answer)
- D. Flushes
COX-2 Selective Inhibitors Explanation: ***Excess water retention***
- **Prostaglandins** generally promote **diuresis** and natriuresis, meaning they help the body excrete water and sodium, rather than retain them [2].
- While some prostaglandins can affect renal blood flow, direct causation of **excess water retention** as a primary side effect is not typical.
*Flushes*
- **Prostaglandins**, particularly **PGE1** and **PGE2**, are potent **vasodilators** and can cause cutaneous vasodilation, leading to **flushing** and a sensation of warmth [3].
- This effect is often mediated by the relaxation of vascular smooth muscle.
*Increased motility of bowel*
- Many **prostaglandins**, especially **PGE** and **PGF** series, stimulate **smooth muscle contraction**, including in the gastrointestinal tract [1].
- This increased contraction can lead to **enhanced bowel motility**, sometimes causing diarrhea or abdominal cramping [1].
*Nausea*
- **Prostaglandins** can have various systemic effects, and activation of pathways in the central nervous system or direct irritation of the GI tract can lead to symptoms like **nausea** and vomiting [1].
- This is a common side effect, especially with systemic administration.
COX-2 Selective Inhibitors Indian Medical PG Question 2: What is the MOA of thalidomide?
- A. Inhibits factor Xa
- B. Prevents folic acid synthesis in bacteria
- C. Inhibits leukotrienes
- D. Angiogenesis inhibitor (Correct Answer)
COX-2 Selective Inhibitors Explanation: ***Angiogenesis inhibitor***
- Thalidomide is known to **inhibit angiogenesis** [1] by blocking the formation of new blood vessels, a key mechanism in its anti-cancer effects.
- It also has **immunomodulatory** [1], [2], [3] and **anti-inflammatory** properties, affecting cytokine production and immune cell function [1], [3].
*Inhibits factor Xa*
- This is the mechanism of action for **direct oral anticoagulants (DOACs)** like rivaroxaban and apixaban, used to prevent blood clot formation.
- Thalidomide does not primarily act on the **coagulation cascade** at this step.
*Prevents folic acid synthesis in bacteria*
- This is the classic mechanism of action for **sulfonamide antibiotics**, which target bacterial enzymes involved in folate metabolism.
- Thalidomide is an **immunomodulatory drug** [2], [3], not an antibiotic that interferes with bacterial folic acid synthesis.
*Inhibits leukotrienes*
- **Leukotriene inhibitors**, such as montelukast and zafirlukast, are used to treat asthma and allergies by blocking inflammatory pathways.
- Thalidomide's primary mechanism is not the direct inhibition of **leukotriene synthesis or receptor binding**.
COX-2 Selective Inhibitors Indian Medical PG Question 3: Which gene is responsible for the production of COX type 3?
- A. COX 3 gene
- B. COX 2 gene
- C. None of the above
- D. COX I gene (Correct Answer)
COX-2 Selective Inhibitors Explanation: ***COX I gene***
- COX-3 is an **alternatively spliced variant** of the **COX-1 gene** (specifically, a splice variant of the COX-1 mRNA that retains intron 1).
- While it was initially thought to be a distinct gene, research has shown that it arises from the same genetic locus as COX-1.
*COX 2 gene*
- The COX-2 gene encodes for the **inducible cyclooxygenase enzyme**, which is responsible for prostaglandin synthesis during inflammation.
- It is a separate gene from COX-1 and has distinct regulatory mechanisms and physiological roles.
*COX 3 gene*
- There is currently **no distinct gene in humans** specifically identified as "COX-3".
- COX-3 refers to a protein isoform derived from the COX-1 gene, not a separate genetic locus.
*None of the above*
- This option is incorrect because COX-3 is indeed derived from the **COX-1 gene** through alternative splicing.
- The existence of COX-3 as a distinct protein product has been demonstrated, although its precise physiological role in humans is still under investigation.
COX-2 Selective Inhibitors Indian Medical PG Question 4: Which of the following medications does not interact with warfarin?
- A. Barbiturate
- B. Oral contraceptive
- C. Cephalosporins
- D. Benzodiazepines (Correct Answer)
COX-2 Selective Inhibitors Explanation: ***Benzodiazepines***
- **Benzodiazepines** are generally considered safe to use with warfarin as they are extensively metabolized in the liver, but they do not typically alter the **cytochrome P450 enzymes** responsible for warfarin metabolism.
- They also do not interfere with **vitamin K recycling** or **platelet function**, which are key mechanisms through which other drugs interact with warfarin.
*Barbiturate*
- **Barbiturates** are **potent inducers of hepatic enzymes**, particularly CYP2C9, which is responsible for metabolizing warfarin.
- This enzyme induction leads to **increased warfarin metabolism**, reducing its anticoagulant effect and necessitating higher warfarin doses.
*Oral contraceptive*
- **Oral contraceptives** can **reduce the anticoagulant effect of warfarin** by inducing clotting factors or inhibiting warfarin metabolism.
- This interaction can increase the risk of **thromboembolic events** in patients on warfarin.
*Cephalosporins*
- Certain **cephalosporins**, especially those with a **methylthiotetrazole (MTT) side chain** (e.g., Cefamandole, Cefoperazone, Moxalactam), can **inhibit vitamin K epoxide reductase**.
- This inhibition leads to a **decrease in vitamin K-dependent clotting factors**, thus potentiating the anticoagulant effect of warfarin and increasing bleeding risk.
COX-2 Selective Inhibitors Indian Medical PG Question 5: Which of the following is an absolute contraindication to the use of nonsteroidal anti-inflammatory drugs (NSAIDs)?
- A. Asthma
- B. Rheumatoid arthritis
- C. Hypertension
- D. Active peptic ulcer disease (Correct Answer)
COX-2 Selective Inhibitors Explanation: ***Active peptic ulcer disease***
- NSAIDs **inhibit cyclooxygenase (COX)** enzymes, which are responsible for producing **prostaglandins** that protect the gastric mucosa.
- In patients with **active peptic ulcers**, this inhibition can lead to serious complications like **bleeding** or **perforation**, making it an **absolute contraindication**.
- A history of peptic ulcer disease is a relative contraindication, but active disease is an absolute contraindication.
*Asthma*
- While NSAIDs can exacerbate asthma in susceptible individuals (**NSAID-exacerbated respiratory disease or aspirin-exacerbated respiratory disease**), it is usually a **relative contraindication** rather than an absolute one.
- This reaction typically affects a specific subset of asthmatic patients (around 10-20%) with aspirin sensitivity and nasal polyps.
*Rheumatoid arthritis*
- NSAIDs are commonly used to **manage pain and inflammation** associated with rheumatoid arthritis.
- It is a condition where NSAIDs are **indicated** for symptom relief, not a contraindication.
*Hypertension*
- NSAIDs can contribute to **elevated blood pressure** due to their effects on renal prostaglandin synthesis, leading to sodium and water retention.
- Although NSAIDs should be used cautiously in hypertensive patients, it is considered a **relative contraindication**, requiring close monitoring rather than an absolute prohibition.
COX-2 Selective Inhibitors Indian Medical PG Question 6: Which of the following is a false statement?
- A. Gastric irritation is more severe with NSAIDs compared to aspirin (Correct Answer)
- B. Acetaminophen does not have anti-inflammatory action
- C. Selective COX-2 inhibitors are contraindicated in postoperative patients
- D. Naproxen has the least cardiovascular risk among NSAIDs
COX-2 Selective Inhibitors Explanation: ***Gastric irritation is more severe with NSAIDs compared to aspirin***
- This statement is **false**. While both NSAIDs and aspirin can cause gastric irritation, **aspirin generally causes more severe gastric irritation** than most NSAIDs.
- Aspirin causes significant GI toxicity due to its **direct irritant effect** on gastric mucosa and **irreversible inhibition of COX-1**, leading to reduced protective gastric mucus and bicarbonate secretion.
- While NSAIDs also inhibit COX-1 causing gastric side effects, their direct irritant effect is typically less pronounced than aspirin.
*Selective COX-2 inhibitors are contraindicated in postoperative patients*
- This statement is **true**. **Selective COX-2 inhibitors** (coxibs like celecoxib, rofecoxib) are contraindicated or used with extreme caution in postoperative patients.
- They increase risk of **cardiovascular thrombotic events** (MI, stroke) by disrupting the prostacyclin-thromboxane balance.
- Postoperative patients have elevated cardiovascular risk, making selective COX-2 inhibitors particularly problematic in this setting.
*Acetaminophen does not have anti-inflammatory action*
- This statement is **true**. Acetaminophen (paracetamol) is primarily an **analgesic** and **antipyretic** agent.
- It has **minimal to no anti-inflammatory effects** at therapeutic doses, unlike NSAIDs.
- Its mechanism of action is predominantly **central** (CNS-based), with weak peripheral COX inhibition that does not translate to clinically significant anti-inflammatory activity.
*Naproxen has the least cardiovascular risk among NSAIDs*
- This statement is **true**. Among traditional NSAIDs, **naproxen is associated with the lowest cardiovascular risk**.
- Studies suggest naproxen may have neutral or even slightly cardioprotective effects compared to other NSAIDs.
- This is attributed to its relatively balanced and sustained COX-1/COX-2 inhibition, causing less disruption of the prostacyclin-thromboxane balance.
COX-2 Selective Inhibitors Indian Medical PG Question 7: A drug that is effective for rheumatoid arthritis but is not appropriate for osteoarthritis is :
- A. Infliximab (Correct Answer)
- B. Rofecoxib
- C. Acetaminophen
- D. Ketorolac
COX-2 Selective Inhibitors Explanation: ***Infliximab***
- **Infliximab** is a **biologic disease-modifying antirheumatic drug (DMARD)**, specifically a TNF-alpha inhibitor, used to treat **autoimmune inflammatory conditions** like rheumatoid arthritis.
- Its mechanism involves modulating the immune system to reduce inflammation, which is not applicable to the **degenerative process** seen in osteoarthritis.
*Rofecoxib*
- **Rofecoxib** was a **COX-2 selective NSAID** used for pain and inflammation in both rheumatoid arthritis and osteoarthritis.
- It was withdrawn from the market due to increased cardiovascular risk, but its initial indication covered both conditions for symptomatic relief.
*Acetaminophen*
- **Acetaminophen** (paracetamol) is an **analgesic** and **antipyretic** primarily used for pain relief in both osteoarthritis and rheumatoid arthritis.
- It does not have significant anti-inflammatory properties and therefore is not a disease-modifying agent for rheumatoid arthritis.
*Ketorolac*
- **Ketorolac** is a potent **non-selective NSAID** commonly used for **acute pain** of moderate to severe intensity.
- It provides symptomatic relief for pain and inflammation in both osteoarthritis and rheumatoid arthritis but does not alter the disease course in either condition.
COX-2 Selective Inhibitors Indian Medical PG Question 8: Which enzyme is irreversibly inhibited by aspirin?
- A. Lipooxygenase
- B. Cyclooxygenase (Correct Answer)
- C. Thromboxane synthase
- D. Phospholipase
COX-2 Selective Inhibitors Explanation: ***Cyclooxygenase***
- **Aspirin** irreversibly inhibits **cyclooxygenase (COX-1 and COX-2)** by acetylating a serine residue in the enzyme's active site.
- This irreversible inhibition prevents the production of **prostaglandins, thromboxane**, and **prostacyclin**, thereby reducing inflammation, pain, fever, and platelet aggregation.
*Lipooxygenase*
- **Lipooxygenase** is involved in the synthesis of **leukotrienes**, which are mediators of inflammation and allergic responses.
- Aspirin does not directly inhibit lipooxygenase; rather, it primarily targets the COX pathway.
*Thromboxane synthase*
- **Thromboxane synthase** is an enzyme downstream of COX, responsible for converting prostaglandin H2 into **thromboxane A2**.
- While aspirin's effect on platelet aggregation is due to reduced thromboxane A2 synthesis via COX inhibition, it does not directly inhibit thromboxane synthase itself.
*Phospholipase*
- **Phospholipase A2** is responsible for releasing **arachidonic acid** from cell membrane phospholipids, which is the initial step in both the cyclooxygenase and lipooxygenase pathways.
- Aspirin does not directly inhibit phospholipase A2; its action occurs later in the cascade.
COX-2 Selective Inhibitors Indian Medical PG Question 9: All are used in the treatment of acute gout except:
- A. Naproxen
- B. Indomethacin
- C. Colchicine
- D. Allopurinol (Correct Answer)
COX-2 Selective Inhibitors Explanation: ***Allopurinol***
- **Allopurinol** is a **xanthine oxidase inhibitor** used for the **long-term prevention** of gout attacks by reducing uric acid levels.
- It is **not used to treat acute gout attacks** because it can paradoxically worsen the acute inflammation by mobilizing urate crystals during a flare.
- Should not be started during an acute attack; if already on therapy, it should be continued.
*Indomethacin*
- **Indomethacin** is a **non-steroidal anti-inflammatory drug (NSAID)** that is highly effective in reducing the inflammation and pain of an acute gout attack.
- It is one of the **most commonly used NSAIDs** for acute gout management.
- Works by inhibiting cyclooxygenase enzymes, thereby reducing **prostaglandin synthesis**, which mediates inflammation.
*Naproxen*
- **Naproxen** is another **NSAID** that is effective in managing acute gout attacks.
- It provides anti-inflammatory and analgesic effects similar to indomethacin but with a longer half-life.
*Colchicine*
- **Colchicine** is an **anti-inflammatory agent** specifically used for both the treatment and prevention of acute gout attacks.
- It works by inhibiting **microtubule polymerization** and reducing the migration of neutrophils to the site of inflammation.
- Most effective when started within **24 hours** of symptom onset.
COX-2 Selective Inhibitors Indian Medical PG Question 10: A patient presents with swelling in MCP joints, and his serum uric acid levels were found to be elevated. His physician prescribed a drug which is considered as the first line agent in the management of this condition. What is the mechanism of this drug?
- A. Uricosuric drug
- B. Pyrimidine antimetabolite
- C. Xanthine oxidase inhibitor (Correct Answer)
- D. Inhibitor of neutrophil recruitment
COX-2 Selective Inhibitors Explanation: ***Xanthine oxidase inhibitor***
- The presentation of **swollen MCP joints** and **elevated uric acid** is highly suggestive of **gout**.
- **Allopurinol**, a **xanthine oxidase inhibitor**, is the **first-line drug** for chronic gout management, reducing uric acid production.
*Uricosuric drug*
- **Uricosuric agents** like **probenecid** increase uric acid excretion, but they are generally **second-line** or used in specific cases, not first-line for most patients.
- These drugs are typically only effective if there is **sufficient renal function** and are contraindicated in patients with a history of **kidney stones**.
*Pyrimidine antimetabolite*
- **Pyrimidine antimetabolites** like **5-fluorouracil** are primarily used in **chemotherapy** for certain cancers by interfering with DNA and RNA synthesis.
- They have **no role** in the treatment of gout or hyperuricemia.
*Inhibitor of neutrophil recruitment*
- **Colchicine**, which inhibits neutrophil migration, is used to treat **acute gout flares** by reducing inflammation, but it's not the first-line agent for **long-term management** of hyperuricemia.
- This mechanism targets the inflammatory response rather than the underlying **uric acid production** or excretion.
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