COX-2 Selective Inhibitors — MCQs
All of the following occurs because of prostaglandin use except?
What is the MOA of thalidomide?
Which gene is responsible for the production of COX type 3?
Which of the following medications does not interact with warfarin?
Which of the following is an absolute contraindication to the use of nonsteroidal anti-inflammatory drugs (NSAIDs)?
Which of the following is a false statement?
A drug that is effective for rheumatoid arthritis but is not appropriate for osteoarthritis is :
Which enzyme is irreversibly inhibited by aspirin?
All are used in the treatment of acute gout except:
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?
COX-2 Selective Inhibitors Indian Medical PG Practice Questions and MCQs
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
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.
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)
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**.
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)
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.
Question 4: Which of the following medications does not interact with warfarin?
- A. Barbiturate
- B. Oral contraceptive
- C. Cephalosporins
- D. Benzodiazepines (Correct Answer)
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.
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)
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.
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
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.
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
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.
Question 8: Which enzyme is irreversibly inhibited by aspirin?
- A. Lipooxygenase
- B. Cyclooxygenase (Correct Answer)
- C. Thromboxane synthase
- D. Phospholipase
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.
Question 9: All are used in the treatment of acute gout except:
- A. Naproxen
- B. Indomethacin
- C. Colchicine
- D. Allopurinol (Correct Answer)
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.
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
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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