Pharmacogenomic Testing — MCQs
Drug of choice for familial hypercholesterolemia?
Which of the following drugs shows nephrotoxicity during administration?
Prader-Willi syndrome and Angelman syndrome are examples of what genetic phenomenon?
A patient on warfarin has a high INR. Which drug likely caused this?
Which of the following is used to detect abnormal gene sequences EXCEPT?
A patient with history of ischemic stroke was started on clopidogrel. However, she had another attack of stroke after 6 months. Which of the following is likely to be responsible for the failure of clopidogrel in this patient?
Which of the following best describes a Type B adverse drug reaction?
Which of the following drugs is metabolized by CYP2D6?
Which of the following combinations can result in severe toxicity due to inhibition of cytochrome P450 enzymes?
All of the following are hormonal agents used in treatment of cancer EXCEPT:
Pharmacogenomic Testing Indian Medical PG Practice Questions and MCQs
Question 1: Drug of choice for familial hypercholesterolemia?
- A. Nicotinic acid
- B. Lovastatin (Correct Answer)
- C. Cholestyramine
- D. Gemfibrozil
Explanation: ***Lovastatin*** - **Statins** (HMG-CoA reductase inhibitors) are the **first-line therapy** for familial hypercholesterolemia as they effectively lower **LDL cholesterol** levels by inhibiting cholesterol synthesis [1]. - While other agents can be used adjunctively, statins like lovastatin are the cornerstone for managing this genetic condition [2]. *Nicotinic acid* - **Nicotinic acid** (niacin) primarily lowers **triglycerides** and increases **HDL cholesterol**, but it is less potent than statins for reducing LDL-C, especially in familial hypercholesterolemia [1]. - Its use is often limited by significant **side effects** like flushing. *Cholestyramine* - **Cholestyramine** is a **bile acid sequestrant** that binds to bile acids in the intestine, preventing their reabsorption and mildly lowering LDL cholesterol. - It is less effective than statins and often causes **gastrointestinal side effects** such as constipation and bloating. *Gemfibrozil* - **Gemfibrozil** is a **fibrate**, primarily used to lower **triglyceride levels** and increase HDL cholesterol. - It has minimal impact on LDL cholesterol compared to statins and is not the primary treatment for familial hypercholesterolemia [2].
Question 2: Which of the following drugs shows nephrotoxicity during administration?
- A. Azathioprine
- B. Tacrolimus (Correct Answer)
- C. Mycophenolate mofetil
- D. Leflunomide
Explanation: ***Tacrolimus*** - **Tacrolimus** is a calcineurin inhibitor and a well-known cause of **nephrotoxicity**, which can manifest as acute kidney injury or chronic renal dysfunction [1], [4]. - Its mechanism involves vasoconstriction of afferent arterioles and direct tubular toxicity, leading to reduced glomerular filtration. *Azathioprine* - **Azathioprine** is an immunosuppressant primarily associated with **bone marrow suppression** (leukopenia, thrombocytopenia) and **hepatotoxicity**, not typically nephrotoxicity [2]. - While it can cause renal impairment in rare cases, it is not a primary mechanism of action. *Mycophenolate mofetil* - **Mycophenolate mofetil (MMF)** is an immunosuppressant that primarily causes **gastrointestinal side effects** (diarrhea, nausea) and **myelosuppression**. - It is generally considered **renal-sparing** and is often used in situations where calcineurin inhibitors are contraindicated due to nephrotoxicity. *Leflunomide* - **Leflunomide** is an immunosuppressant used in rheumatoid arthritis, known for causing **hepatotoxicity**, **hypertension**, and **teratogenicity** [3]. - While it can affect various organ systems, direct and significant nephrotoxicity is not a prominent adverse effect.
Question 3: Prader-Willi syndrome and Angelman syndrome are examples of what genetic phenomenon?
- A. Gene Knockout
- B. Impaired DNA repair
- C. Genomic Imprinting (Correct Answer)
- D. RNA interference
Explanation: ***Genomic Imprinting*** - **Genomic imprinting** is an epigenetic phenomenon where certain genes are expressed in a **parent-of-origin-specific manner**. - In Prader-Willi syndrome, the disease results from the loss of function of specific genes on chromosome 15 (15q11-q13) inherited from the father, while Angelman syndrome results from the loss of function of a different gene (UBE3A) in the same region, but inherited from the mother. *RNA interference* - **RNA interference** is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. - This process is not directly responsible for the parent-of-origin-specific expression patterns observed in these syndromes. *Gene Knockout* - A **gene knockout** is a genetic technique in which an organism's genes are made inoperative. - While it involves modifying gene function, it does not explain the differential expression based on parental origin. *Impaired DNA repair* - **Impaired DNA repair** refers to defects in the mechanisms that correct DNA damage. - This can lead to increased mutations and conditions like cancer, but it is not the underlying mechanism for Prader-Willi or Angelman syndromes.
Question 4: A patient on warfarin has a high INR. Which drug likely caused this?
- A. Amiodarone (Correct Answer)
- B. Phenytoin
- C. Carbamazepine
- D. Rifampicin
Explanation: ***Amiodarone*** - Amiodarone is a well-known inhibitor of **CYP2C9**, the primary enzyme responsible for the metabolism of **S-warfarin**, the more potent enantiomer of warfarin. - Inhibition of warfarin metabolism leads to increased warfarin levels, thereby enhancing its anticoagulant effect and causing a **higher INR**. *Phenytoin* - Phenytoin is an **enzyme inducer**, primarily of **CYP2C9** and **CYP3A4**. - Its interaction with warfarin typically leads to **decreased warfarin levels** and a **lower INR**, reducing the anticoagulant effect. *Carbamazepine* - Carbamazepine is a potent **enzyme inducer**, particularly of **CYP3A4** and **CYP2C9**. - Like phenytoin, it generally leads to **increased warfarin metabolism** and a **reduced INR**, thereby decreasing its anticoagulant efficacy. *Rifampicin* - Rifampicin is a strong **inducer of hepatic cytochrome P450 enzymes**, especially **CYP3A4** and **CYP2C9**. - Its co-administration with warfarin significantly **increases warfarin metabolism**, resulting in **lower warfarin concentrations** and a **decreased INR**.
Question 5: Which of the following is used to detect abnormal gene sequences EXCEPT?
- A. RFLP analysis
- B. Pyrosequencing
- C. Flow cytometry (Correct Answer)
- D. FISH
Explanation: ***Flow cytometry*** - **Flow cytometry** is primarily used to analyze **cell populations** based on their physical and biochemical characteristics (e.g., size, granularity, and protein expression) by passing them single file through a laser beam, not for direct gene sequencing. - It detects and quantifies cells labeled with **fluorescent antibodies**, making it useful for immunophenotyping, cell sorting, and DNA content analysis, but not for identifying specific gene sequences or mutations. *RFLP analysis* - **Restriction fragment length polymorphism (RFLP) analysis** detects variations in **DNA sequences** by using **restriction enzymes** to cut DNA at specific sites. - Differences in fragment lengths indicate **polymorphisms** or **mutations** within the recognition sites, thereby identifying abnormal gene sequences. *Pyrosequencing* - **Pyrosequencing** is a method of **DNA sequencing** that determines the sequence of nucleotides by detecting the release of pyrophosphate during DNA synthesis. - It is used to identify **single nucleotide polymorphisms (SNPs)** and **short genetic variations**, making it suitable for detecting abnormal gene sequences. *FISH* - **Fluorescence in situ hybridization (FISH)** uses **fluorescently labeled DNA probes** that bind to specific complementary **DNA sequences** on chromosomes. - It is a powerful cytogenetic technique for detecting **chromosomal abnormalities**, such as deletions, translocations, and amplifications, thereby identifying abnormal gene sequences.
Question 6: A patient with history of ischemic stroke was started on clopidogrel. However, she had another attack of stroke after 6 months. Which of the following is likely to be responsible for the failure of clopidogrel in this patient?
- A. Upregulation of CYP1A1
- B. Downregulation of CYP2E1
- C. Downregulation of CYP2C19 (Correct Answer)
- D. Downregulation of CYP2D6
Explanation: ***Reduced function/Loss of function of CYP2C19*** - **Clopidogrel** is a **prodrug** that requires activation by **hepatic cytochrome P450 (CYP) enzymes**, primarily **CYP2C19**, to its active metabolite. - **Genetic polymorphisms** causing **reduced function or loss of function of CYP2C19** (e.g., CYP2C19*2, *3 alleles) result in insufficient conversion of clopidogrel to its active form, leading to **clopidogrel resistance** and increased risk of thrombotic events like recurrent stroke. - These **poor metabolizers** have significantly reduced antiplatelet response to standard clopidogrel doses. *Upregulation of CYP1A1* - **CYP1A1** is involved in the metabolism of various xenobiotics but plays a **minimal role** in clopidogrel activation. - Upregulation of CYP1A1 would not be a primary factor in clopidogrel failure as it is not the main enzyme responsible for its bioactivation. *Downregulation of CYP2E1* - **CYP2E1** is primarily involved in the metabolism of small organic molecules, some drugs, and toxins, and has **no significant role** in the bioactivation of clopidogrel. - Therefore, changes in its expression would not impact clopidogrel's efficacy. *Downregulation of CYP2D6* - **CYP2D6** is a major enzyme involved in the metabolism of many psychoactive drugs, beta-blockers, and opioids, but plays only a **minor role** in clopidogrel activation compared to CYP2C19. - Downregulation of CYP2D6 would not be the primary cause of clopidogrel failure.
Question 7: Which of the following best describes a Type B adverse drug reaction?
- A. Augmented effect of drug
- B. Effect seen on chronic use of drug
- C. Delayed effect of drug
- D. Unpredictable bizarre reaction (Correct Answer)
Explanation: ***Unpredictable bizarre reaction*** - Type B reactions are **unpredictable**, **bizarre**, and not directly related to the drug's known pharmacological actions. - They often involve **immunological reactions** or genetic predispositions, such as allergies or idiosyncratic responses. *Augmented effect of drug* - This describes a **Type A** adverse drug reaction, which is predictable and results from an **exaggerated pharmacological effect** of the drug. - It is typically dose-dependent and can be managed by adjusting the dosage. *Effect seen on chronic use of drug* - This description can apply to several types of adverse reactions, but it commonly relates to **Type C (chronic) reactions**, where effects occur only after prolonged exposure. - These reactions might be due to **cumulative toxicity** or adaptive changes in the body. *Delayed effect of drug* - This aligns with **Type D (delayed) adverse drug reactions**, which manifest long after the drug exposure has ended or after a period of latency. - Examples include **carcinogenesis** or teratogenesis, occurring months or years later.
Question 8: Which of the following drugs is metabolized by CYP2D6?
- A. Propranolol (Correct Answer)
- B. Warfarin
- C. Statins
- D. Amiodarone
Explanation: ***Correct Answer: Propranolol*** - **Propranolol** is a non-selective beta-blocker that undergoes extensive **first-pass metabolism**, primarily via the **CYP2D6** and CYP1A2 enzymes. - Genetic variations in **CYP2D6** can significantly affect propranolol's metabolism, leading to altered drug levels and therapeutic responses. *Incorrect: Warfarin* - **Warfarin** is predominantly metabolized by **CYP2C9**, with minor contributions from other CYP enzymes. - Genetic polymorphisms in **CYP2C9** are a major factor in determining individual warfarin dose requirements. *Incorrect: Statins* - Most **statins** (e.g., simvastatin, lovastatin, atorvastatin) are primarily metabolized by **CYP3A4**. - **Fluvastatin** is an exception, being mainly metabolized by CYP2C9, while **rosuvastatin** is largely unmetabolized. *Incorrect: Amiodarone* - **Amiodarone** is primarily metabolized by **CYP3A4** and to a lesser extent by CYP2C8. - Due to its **long half-life** and extensive metabolism, amiodarone has numerous drug interactions, often involving CYP3A4 inhibition.
Question 9: Which of the following combinations can result in severe toxicity due to inhibition of cytochrome P450 enzymes?
- A. Amiodarone + Atorvastatin
- B. Carbamazepine + Atorvastatin
- C. Atorvastatin + Itraconazole (Correct Answer)
- D. Phenytoin + Atorvastatin
Explanation: ***Atorvastatin + Itraconazole*** - **Itraconazole** is a potent inhibitor of **CYP3A4**, the primary enzyme responsible for atorvastatin's metabolism. - Co-administration leads to significantly increased **atorvastatin plasma concentrations**, raising the risk of severe side effects like **rhabdomyolysis** and **hepatotoxicity**. *Amiodarone + Atorvastatin* - **Amiodarone** is a moderate **CYP3A4 inhibitor** and can increase atorvastatin levels, but the inhibition is **less potent** than itraconazole. - While this combination does carry a risk and requires dose adjustment, the interaction is **less severe** compared to the potent inhibition seen with itraconazole. - The direct CYP inhibition leading to severe atorvastatin toxicity is less pronounced than with itraconazole. *Carbamazepine + Atorvastatin* - **Carbamazepine** is a potent **CYP3A4 inducer**, meaning it would increase the metabolism of atorvastatin, potentially *decreasing* its efficacy rather than causing toxicity through inhibition. - This interaction would typically lead to subtherapeutic atorvastatin levels, rather than severe toxicity. *Phenytoin + Atorvastatin* - **Phenytoin** is also a potent **CYP3A4 inducer**, similar to carbamazepine. - Concurrent use would likely lead to enhanced metabolism and **reduced efficacy of atorvastatin**, not increased toxicity due to enzyme inhibition.
Question 10: All of the following are hormonal agents used in treatment of cancer EXCEPT:
- A. Cabergoline
- B. Leuprolide
- C. Irinotecan (Correct Answer)
- D. Anastrozole
Explanation: ***Irinotecan*** - **Irinotecan** is a **chemotherapeutic agent** that acts as a **topoisomerase I inhibitor**, interfering with DNA replication and repair. - It works through a **cytotoxic mechanism** directly killing cancer cells, rather than modulating hormonal pathways. *Cabergoline* - **Cabergoline** is a **dopamine agonist** primarily used to treat **prolactinomas**, which are prolactin-producing pituitary tumors. - While it treats a tumor, its mechanism is **hormonal modulation** by reducing prolactin secretion, not direct cytotoxicity. *Anastrozole* - **Anastrozole** is an **aromatase inhibitor** used in estrogen receptor-positive breast cancer. - It works by **blocking the conversion of androgens to estrogens**, thereby reducing estrogen levels that fuel cancer growth. *Leuprolide* - **Leuprolide** is a **GnRH agonist** used in prostate cancer, breast cancer, and other hormone-sensitive conditions. - It initially stimulates, then continuously downregulates, the **pituitary gland's production of LH and FSH**, leading to reduced testosterone or estrogen levels.
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