Drug Interactions Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Drug Interactions. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Drug Interactions Indian Medical PG Question 1: Match List-I with List-II and select the correct answer using the code given below the Lists:
- A. A→4 B→3 C→1 D→2
- B. A→4 B→2 C→3 D→1
- C. A→3 B→4 C→1 D→2
- D. A→4 B→1 C→3 D→2 (Correct Answer)
Drug Interactions Explanation: **A→4 B→1 C→3 D→2**
- This option correctly matches each endocrine gland with its primary hormone: the **pineal gland** produces **melatonin**, the **testis** produces **testosterone**, the **adrenal gland** produces **cortisol**, and the **ovary** produces **estrogen**.
- These pairings are fundamental to understanding the basic functions of the endocrine system.
*A→4 B→3 C→1 D→2*
- This option incorrectly matches the **testis** with **cortisol** (should be testosterone) and the **adrenal gland** with **melatonin** (should be cortisol).
- Cortisol is a steroid hormone produced by the adrenal cortex, while melatonin from the pineal gland regulates sleep-wake cycles.
*A→4 B→2 C→3 D→1*
- This option incorrectly matches the **testis** with **estrogen** (should be testosterone) and the **ovary** with **melatonin** (should be estrogen).
- Estrogen is the primary female sex hormone, while testosterone is the primary male sex hormone.
*A→3 B→4 C→1 D→2*
- This option incorrectly matches the **pineal gland** with **cortisol** (should be melatonin) and the **testis** with **estrogen** (should be testosterone).
- The pineal gland is known for its role in circadian rhythms through melatonin production, not stress response hormones like cortisol.
Drug Interactions Indian Medical PG Question 2: Warfarin's mechanism of action is
- A. Inhibiting Vitamin K dependent carboxylation (Correct Answer)
- B. Chelating calcium ions
- C. Inhibiting antithrombin III activity
- D. Inhibiting thrombin activity
Drug Interactions Explanation: ***Inhibiting Vitamin K dependent carboxylation***
- **Warfarin** acts as an antagonist to **vitamin K**, competitively inhibiting the enzyme **vitamin K epoxide reductase**.
- This prevents the **gamma-carboxylation** of vitamin K-dependent clotting factors (II, VII, IX, X, and proteins C and S), rendering them biologically inactive.
*Chelating calcium ions*
- **Calcium ions** are essential cofactors in the coagulation cascade, but warfarin does not directly affect their concentration or chelate them.
- Anticoagulants that chelate calcium, such as **citrate**, are typically used *in vitro* (e.g., in blood collection tubes), not systemically.
*Inhibiting antithrombin III activity*
- This mechanism describes the action of **heparin** and its derivatives, which enhance the natural anticoagulant activity of **antithrombin III**.
- Warfarin's primary action is on vitamin K metabolism, not on antithrombin III potentiation.
*Inhibiting thrombin activity*
- Direct thrombin inhibitors (**DTIs**), such as dabigatran and argatroban, directly bind to and inhibit the activity of **thrombin (factor IIa)**.
- Warfarin's action is upstream in the coagulation cascade, affecting the synthesis of multiple clotting factors, including prothrombin (the precursor to thrombin).
Drug Interactions Indian Medical PG Question 3: Which of the following medications does not interact with warfarin?
- A. Barbiturate
- B. Oral contraceptive
- C. Cephalosporins
- D. Benzodiazepines (Correct Answer)
Drug Interactions 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.
Drug Interactions Indian Medical PG Question 4: Which of the following is the platinum-based chemotherapeutic agent used as first-line treatment for ovarian carcinoma?
- A. Cyclophosphamide
- B. Methotrexate
- C. Cisplatin (Correct Answer)
- D. Dacarbazine
Drug Interactions Explanation: ***Cisplatin***
- **Cisplatin** is a platinum-based chemotherapy drug that forms **DNA cross-links**, inhibiting DNA synthesis and leading to the death of rapidly dividing cells, making it highly effective against **ovarian carcinoma**.
- It is a cornerstone of chemotherapy regimens for ovarian cancer, often used in combination with other agents such as paclitaxel.
*Methotrexate*
- **Methotrexate** is an **antimetabolite** that inhibits dihydrofolate reductase, thereby interfering with DNA synthesis.
- While it is used in various cancers like leukemia, lymphoma, and some solid tumors (e.g., breast cancer, gestational trophoblastic disease), it is **not a primary recommended drug for ovarian carcinoma**.
*Cyclophosphamide*
- **Cyclophosphamide** is an **alkylating agent** that causes DNA damage, leading to cell death.
- It is used in many cancers, including lymphoma, breast cancer, and some leukemias, but it is **not a first-line or primary agent for ovarian carcinoma** in contemporary treatment guidelines.
*Dacarbazine*
- **Dacarbazine** is an **alkylating agent** primarily used in the treatment of **malignant melanoma** and Hodgkin lymphoma.
- It is **not indicated for the treatment of ovarian carcinoma**.
Drug Interactions Indian Medical PG Question 5: Which of the following statements represents the most clinically significant aspect of drug metabolism?
- A. Most common enzyme involved is CYP 3A4/5 (Correct Answer)
- B. Glucuronidation is a phase II reaction
- C. Reduction is a phase I reaction
- D. Cytochrome P450 is involved in phase I reactions
Drug Interactions Explanation: ***Most common enzyme involved is Cyp 3A4/5***
- CYP3A4/5 is the **most abundant and clinically significant** cytochrome P450 enzyme, responsible for metabolizing approximately **50% of all clinically used drugs**.
- Its widespread involvement means variations in its activity (due to **genetics, drug interactions, or disease**) have a major impact on drug efficacy and toxicity.
*Glucuronidation is a phase II reaction*
- While correct that glucuronidation is a **Phase II metabolic reaction**, this statement describes a biochemical classification rather than a clinically significant aspect compared to the involvement of CYP3A4/5.
- Phase II reactions generally involve **conjugation** to increase water solubility and facilitate excretion, but they do not collectively account for as many drug interactions as CYP3A4/5 alone.
*Reduction is a phase I reaction*
- This statement is factually correct as **reduction** is indeed a **Phase I metabolic reaction**.
- However, it represents a generic classification of a metabolic pathway and doesn't highlight the specific clinical importance or prevalence of a particular enzyme or reaction in drug metabolism.
*Cytochrome P450 is involved in phase I reactions*
- This is true; the **cytochrome P450 system** is the primary enzyme system for **Phase I metabolism**, which introduces or exposes polar groups to make drugs more reactive.
- While fundamentally important, this statement is too broad; it does not specify the most clinically significant *aspect* or *enzyme* within the P450 system compared to directly identifying CYP3A4/5.
More Drug Interactions Indian Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
