Pharmacogenomics of Drug Transporters — MCQs
Pharmacodynamics deals with:-
Which among the following is the false statement regarding statins?
Which drug is metabolized by glutathionation?
Which of the following is not considered a pharmacogenetic condition?
Which statin is considered most potent based on mg-to-mg LDL reduction capability?
Choose the correct options regarding the route of administration and bioavailability. A- Intravenous =1 B- 0.75< Oral <1 C-0.75 <IM ≤ 1 D- 0.75<SC ≤ 1 IM - Intramuscular SC- Subcutaneous
A patient on atorvastatin presents with myalgia; which test is recommended?
Major mechanism of transport of drugs across biological membranes is:
Which of the following is the platinum-based chemotherapeutic agent used as first-line treatment for ovarian carcinoma?
Mechanism of action of allopurinol is
Pharmacogenomics of Drug Transporters Indian Medical PG Practice Questions and MCQs
Question 1: Pharmacodynamics deals with:-
- A. Latency of onset
- B. Mechanism of action of a drug (Correct Answer)
- C. Transport of drug across the biological membranes
- D. Mode of excretion of a drug
Explanation: Detailed study of the **Mechanism of action of a drug** [1][2] - **Pharmacodynamics** describes what the **drug does to the body**, including its **molecular targets** and biochemical effects [3]. - This involves the study of the drug's mechanisms to produce its therapeutic or toxic effects [2]. *Latency of onset* - **Latency of onset** refers to the time it takes for a drug to start producing its effects, which is a pharmacokinetic rather than a pharmacodynamic parameter. - It deals with the drug's absorption and distribution rather than its interaction with the body once it reaches its site of action. *Transport of drug across the biological membranes* - The **transport of drugs across biological membranes** is a key aspect of **pharmacokinetics**, specifically absorption and distribution [1]. - This process determines how much drug reaches its target site, not how it interacts with the target. *Mode of excretion of a drug* - The **mode of excretion** of a drug (e.g., renal, hepatic) falls under **pharmacokinetics**, addressing how the body gets rid of the drug. - This process influences the drug's duration of action and elimination half-life, not its mechanism of action.
Question 2: Which among the following is the false statement regarding statins?
- A. These drugs should not be stopped even in severe conditions like injury, surgery etc.
- B. Although HMG-CoA reductase inhibitors substantially reduce the risk of cardiovascular events, there is mild increase in lipoprotein a (Lpa) levels.
- C. With the long term use, there is slight increase in the incidence of type 2 diabetes mellitus.
- D. They can be given with verapamil and other enzyme inhibitors (Correct Answer)
Explanation: ***They can be given with verapamil and other enzyme inhibitors*** - This statement is **FALSE** and is the correct answer because **verapamil** (a moderate CYP3A4 inhibitor) and other potent CYP3A4 inhibitors like **clarithromycin** or **azole antifungals** can significantly increase statin concentrations, raising the risk of adverse effects like **myopathy** and **rhabdomyolysis**. - **Co-administration** of statins with these inhibitors generally requires careful dose adjustments or avoidance, as they increase the systemic exposure to most statins (especially **simvastatin**, **atorvastatin**, and **lovastatin**). *These drugs should not be stopped even in severe conditions like injury, surgery etc.* - This statement could be considered false in certain contexts, as statins **can be temporarily held** in acute, severe conditions like sepsis, major trauma, or complex surgery, especially if there's a concern for **acute kidney injury** or **rhabdomyolysis** [1]. - However, in most routine surgical situations, statins are typically continued due to their cardiovascular protective effects. *Although HMG-CoA reductase inhibitors substantially reduce the risk of cardiovascular events, there is mild increase in lipoprotein a (Lpa) levels.* - This statement is **TRUE**. Statins are associated with a **modest increase in Lp(a) levels** (approximately 10-20%), which has been consistently demonstrated in clinical studies [2]. - While statins effectively lower **LDL cholesterol**, Lp(a) levels are largely **genetically determined** and may paradoxically increase with statin therapy, though this effect is generally considered clinically insignificant compared to the overall cardiovascular benefits [2]. *With the long term use, there is slight increase in the incidence of type 2 diabetes mellitus.* - This statement is **TRUE**. Long-term statin use is associated with a **small but statistically significant increase** in the risk of developing **type 2 diabetes mellitus** (approximately 9-12% increased risk), particularly in individuals with pre-existing risk factors like **metabolic syndrome**. - This risk, however, is generally **outweighed by the cardiovascular benefits** of statin therapy in at-risk patients, making it an acceptable trade-off.
Question 3: Which drug is metabolized by glutathionation?
- A. Nicotinic acid
- B. Fosfomycin
- C. Benzodiazepines
- D. Dapsone (Correct Answer)
Explanation: ***Dapsone***- **Dapsone** undergoes hepatic metabolism via **N-hydroxylation** by CYP450 enzymes (particularly CYP2E1 and CYP3A4), forming reactive **hydroxylamine metabolites**.- These reactive metabolites are toxic and can cause **methemoglobinemia** and **hemolysis**.- **Glutathione conjugation (glutathionation)** serves as an important **detoxification pathway** for these reactive dapsone metabolites [1].- Individuals with **glutathione deficiency** (such as G6PD deficiency) are at increased risk of dapsone-induced hemolytic anemia [2].*Fosfomycin*- **Fosfomycin** is primarily eliminated by the kidneys as an **unchanged drug** (up to 90% excreted unchanged in urine).- It undergoes **minimal hepatic metabolism** and does NOT undergo significant glutathionation.- Its primary route of elimination is **renal excretion** via glomerular filtration.*Benzodiazepines*- **Benzodiazepines** are primarily metabolized in the liver via **CYP450 enzymes** (Phase I oxidation) followed by **glucuronidation** (Phase II conjugation).- They do NOT undergo glutathionation as a significant metabolic pathway.*Nicotinic acid*- **Nicotinic acid** (niacin) undergoes conjugation with **glycine** to form nicotinuric acid and **methylation** to form N-methylnicotinamide.- It does NOT undergo glutathione conjugation.
Question 4: Which of the following is not considered a pharmacogenetic condition?
- A. Adenosine deaminase deficiency (Correct Answer)
- B. Coumarin insensitivity
- C. G6PD deficiency
- D. Malignant hyperthermia
Explanation: ***Adenosine deaminase deficiency*** - **Adenosine deaminase deficiency** (ADA deficiency) is an **autosomal recessive** metabolic disorder causing severe immunodeficiency, primarily affecting gene function rather than drug response. - While it can be treated with enzyme replacement therapies or gene therapy, it is not primarily characterized by an altered response to standard therapeutic drugs. *Coumarin insensitivity* - **Coumarin insensitivity** refers to an individual's reduced response to **warfarin (a coumarin derivative)**, requiring higher doses to achieve effective anticoagulation. - This is a well-documented **pharmacogenetic condition**, often linked to variations in genes like *CYP2C9* and *VKORC1*. *G6PD deficiency* - **Glucose-6-phosphate dehydrogenase (G6PD) deficiency** is an X-linked genetic disorder that can lead to **hemolytic anemia** upon exposure to certain drugs (e.g., antimalarials, sulfonamides, aspirin) and fava beans [1]. - It is a classic example of a **pharmacogenetic condition** where genetic variations dictate drug-induced adverse reactions [1]. *Malignant hyperthermia* - **Malignant hyperthermia** is a life-threatening, inherited disorder triggered by certain **inhalation anesthetics** (e.g., halothane, isoflurane) and the **depolarizing muscle relaxant succinylcholine**. - This condition is caused by mutations in genes involved in calcium regulation in muscle cells (e.g., *RYR1*) and is a critical **pharmacogenetic response**.
Question 5: Which statin is considered most potent based on mg-to-mg LDL reduction capability?
- A. Simvastatin
- B. Pravastatin
- C. Rosuvastatin (Correct Answer)
- D. Atorvastatin
Explanation: ***Rosuvastatin*** - **Rosuvastatin** is known for its high potency, achieving significant **LDL-C reduction** at relatively low doses. - It is often considered the most potent statin on a **milligram-to-milligram basis**. *Simvastatin* - **Simvastatin** is a moderate-intensity statin, not as potent as rosuvastatin or atorvastatin in reducing LDL-C. - While effective, it typically requires higher doses to achieve comparable **LDL-C reductions** seen with high-potency statins. *Pravastatin* - **Pravastatin** is a hydrophilic statin, generally considered to be of lower potency compared to other statins like rosuvastatin and atorvastatin. - It is often used in patients with **hepatic dysfunction** due to its different metabolic profile but offers less aggressive **LDL-C reduction**. *Atorvastatin* - **Atorvastatin** is a high-intensity statin, very effective in reducing LDL-C, and often used for aggressive lipid lowering. - While highly potent, **atorvastatin** is generally considered slightly less potent than **rosuvastatin** on a mg-to-mg basis, though both are used for high-intensity lipid therapy.
Question 6: Choose the correct options regarding the route of administration and bioavailability. A- Intravenous =1 B- 0.75< Oral <1 C-0.75 <IM ≤ 1 D- 0.75<SC ≤ 1 IM - Intramuscular SC- Subcutaneous
- A. A and D
- B. A and C
- C. A, C, D (Correct Answer)
- D. A, B, D
Explanation: ***A, C, D*** - Intravenous (IV) administration has **100% bioavailability** because the drug enters the systemic circulation directly, bypassing any absorption barriers. - Intramuscular (IM) and subcutaneous (SC) routes generally have **high bioavailability**, often between 75% and 100%, as drugs are absorbed directly into the bloodstream without first-pass metabolism. *A and D* - While options A and D are correct, this choice is incomplete as option C is also a correct statement regarding bioavailability. - IM administration typically results in high systemic bioavailability, similar to SC, making its exclusion here incorrect. *A and C* - While options A and C are correct, this choice is incomplete as option D is also a correct statement regarding bioavailability. - Subcutaneous administration also generally results in high bioavailability, as absorption tends to be complete. *A, B, D* - While options A and D are correct, option B is typically incorrect for oral bioavailability. - Oral bioavailability of many drugs is often less than 0.75 (75%) due to factors like **first-pass metabolism** and incomplete absorption in the gastrointestinal tract.
Question 7: A patient on atorvastatin presents with myalgia; which test is recommended?
- A. Liver function test
- B. Blood urea nitrogen
- C. Serum potassium
- D. Creatine kinase (Correct Answer)
Explanation: ***Creatine kinase*** - **Myalgia** in a patient on **atorvastatin** raises concern for **statin-induced myopathy**, which can range from mild muscle aches to severe **rhabdomyolysis** [1]. - **Creatine kinase (CK)** levels are commonly used to assess muscle damage, with significantly elevated levels (e.g., >10 times normal) indicating rhabdomyolysis [1]. *Liver function test* - While atorvastatin can cause **hepatic dysfunction**, **myalgia** is not a primary symptom of liver injury [1]. - **Liver function tests (LFTs)** would be more relevant if the patient presented with jaundice, dark urine, or other signs of liver damage [1]. *Blood urea nitrogen* - **Blood urea nitrogen (BUN)** is a marker of **kidney function**, not directly related to muscle pain or statin-induced myopathy. - While severe **rhabdomyolysis** can lead to **acute kidney injury (AKI)**, BUN would be checked *after* CK levels indicate significant muscle breakdown. *Serum potassium* - **Serum potassium** levels are important for **cardiac and muscle function**, but myalgia itself does not directly indicate a potassium imbalance. - **Hyperkalemia** can occur secondary to severe **rhabdomyolysis** due to the release of intracellular potassium from damaged muscle cells, but CK is the initial diagnostic test for muscle injury.
Question 8: Major mechanism of transport of drugs across biological membranes is:
- A. Passive diffusion (Correct Answer)
- B. Facilitated diffusion
- C. Active transport
- D. Endocytosis
Explanation: ***Passive diffusion*** - This is the **most common mechanism** for drug transport across biological membranes, especially for **lipid-soluble** drugs. - It occurs down a **concentration gradient** and does not require energy or carrier proteins. *Facilitated diffusion* - This process requires **carrier proteins** to move drugs across membranes, but it still occurs down a **concentration gradient** and does not consume energy directly. - It handles substances that are **too large or too polar** to cross by passive diffusion, but it is not the primary mechanism for most drugs. *Active transport* - This mechanism uses **carrier proteins** and **expends energy (ATP)** to move drugs against their **concentration gradient**. - It is important for the transport of specific drugs, but it is not the predominant mode for the majority of drug molecules. *Endocytosis* - This involves the **engulfment of large molecules** or particles by the cell membrane, forming vesicles. - It is a less common mechanism for drug absorption, primarily used for **very large molecules** like proteins or nanoparticles.
Question 9: 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
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**.
Question 10: Mechanism of action of allopurinol is
- A. Recombinant uricase
- B. Decrease chemotaxis
- C. Increase uric acid excretion
- D. Xanthine oxidase inhibition (Correct Answer)
Explanation: ***Xanthine oxidase inhibition*** - **Allopurinol** acts as a **structural analog of hypoxanthine** and competitively inhibits the enzyme **xanthine oxidase**. - By inhibiting **xanthine oxidase**, allopurinol prevents the conversion of hypoxanthine to xanthine and then to uric acid, thereby **decreasing uric acid production**. *Recombinant uricase* - **Recombinant uricase** (e.g., rasburicase, pegloticase) is an enzyme that catalyzes the breakdown of existing uric acid into allantoin, a more soluble compound. - This mechanism is distinct from allopurinol, which **prevents uric acid formation**. *Decrease chemotaxis* - Medications that **decrease chemotaxis**, such as **colchicine**, work by interfering with the migration of neutrophils to sites of inflammation, which is useful in acute gout flares. - This is an **anti-inflammatory mechanism**, not related to uric acid synthesis or excretion. *Increase uric acid excretion* - Drugs that **increase uric acid excretion** are known as **uricosurics** (e.g., probenecid, lesinurad). - These agents act on the renal tubules to **inhibit uric acid reabsorption**, thus promoting its elimination from the body.
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