Pharmacogenomics Practice Questions

Q: In pseudocholinesterase deficiency, which drug should be used cautiously?

Succinylcholine. ***Succinylcholine*** - **Succinylcholine** is primarily metabolized by **pseudocholinesterase** (also known as butyrylcholinesterase). - In individuals with **pseudocholinesterase deficiency**, the metabolism of succinylcholine is significantly delayed, leading to **prolonged neuromuscular blockade** and extended paralysis. *Barbiturates* - **Barbiturates** are mainly metabolized by the **hepatic cytochrome P450 system** and do not depend on pseudocholinesterase for their breakdown. - Their metabolism would not be significantly affected by pseudocholinesterase deficiency. *Halothane (an inhalational anesthetic)* - **Halothane** is primarily metabolized by the **hepatic cytochrome P450 system** and excreted via the lungs. - Its metabolism is unrelated to **pseudocholinesterase activity**. *Gallamine (a neuromuscular blocker)* - **Gallamine** is a **nondepolarizing neuromuscular blocker** that is primarily eliminated by **renal excretion** as an unchanged drug. - Its metabolism and elimination are independent of **pseudocholinesterase**.

Q: HLA-B*5701 is an allele associated with hypersensitivity to abacavir. Which of the following is the parent allele of HLA-B*5701?

HLA-B*57. ***HLA-B\*57*** - **HLA-B*57** is the parent allele for **HLA-B*5701**, indicating it is the broader serotype under which specific alleles like *5701 are classified [1]. - The notation **HLA-B\*57** signifies a specific **HLA class I** allele group [1]. *HLA-B\*5* - This option is **incomplete** as an HLA allele notation; it lacks the specific group designation often indicated by two or three digits following the asterisk. - While "B5" exists as a serotype, **"HLA-B*5"** itself is not a standard, complete allele designation reflecting a specific gene variant. *HLA-B\*51* - **HLA-B\*51** is a specific **HLA class I** allele, but it is not directly related to or the parent group of **HLA-B\*5701**. - It is known to be associated with Behcet's disease, a different clinical condition not related to abacavir hypersensitivity. *HLA-DQ2* - **HLA-DQ2** is an allele of **HLA class II**, while **HLA-B\*5701** is an **HLA class I** allele. - Though both are HLA alleles, they belong to different classes and are associated with different disease contexts, with **HLA-DQ2 typically linked to celiac disease**.

Q: Hemolysis in G6PD deficiency is precipitated by all of the following except:

Penicillin. ***Penicillin*** - **Penicillin** is generally considered safe in individuals with G6PD deficiency and typically does not precipitate **hemolysis**. - Its mechanism of action does not involve the generation of **oxidative stress** that would overwhelm the deficient G6PD pathway. *Dapsone* - **Dapsone** is known to cause **oxidative stress** in red blood cells, making it a strong precipitating agent for hemolysis in G6PD deficient individuals. - It is an **antimicrobial** agent often used in conditions like leprosy. *Cotrimoxazole* - **Cotrimoxazole**, a combination of **trimethoprim** and **sulfamethoxazole**, is a potent oxidizing agent. - It can induce significant **hemolysis** in patients with G6PD deficiency due to its oxidative properties. *Quinine* - **Quinine**, an **antimalarial** drug, is another agent that can cause oxidative stress in red blood cells. - It is recognized as a drug that can precipitate **hemolytic crises** in G6PD deficient individuals.

Q: The risk of carbamazepine-induced Stevens-Johnson syndrome is increased in the presence of which of the following genes?

HLA-B* 1502. ***HLA-B\* 1502*** - The **HLA-B\*1502** allele is strongly associated with an increased risk of **carbamazepine-induced Stevens-Johnson syndrome (SJS)** and **toxic epidermal necrolysis (TEN)**, particularly in individuals of Asian ancestry. - Screening for this allele is often recommended before initiating **carbamazepine** in at-risk populations. *HLA-B\* 5801* - The **HLA-B\*5801** allele is associated with an increased risk of **allopurinol-induced severe cutaneous adverse reactions (SCARs)**, including SJS and TEN. - It is not directly linked to carbamazepine-induced SJS. *HLA-B\* 5701* - The **HLA-B\*5701** allele is strongly associated with a higher risk of **abacavir hypersensitivity reaction** [1]. - It is recommended to screen for this allele before starting abacavir therapy. *HLA-B 27* - **HLA-B27** is primarily associated with **seronegative spondyloarthropathies**, such as **ankylosing spondylitis** and **reactive arthritis**. - It does not have a known association with carbamazepine-induced SJS.

Q: Which of the following is not considered a pharmacogenetic condition?

Adenosine deaminase deficiency. ***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 1

In pseudocholinesterase deficiency, which drug should be used cautiously?

Accepted Answer

Succinylcholine

Answer

Barbiturates

Answer

Gallamine

Answer

Halothane

Question 2

What does the Dibucaine number indicate in clinical practice?

Accepted Answer

Indicates the percentage inhibition of pseudocholinesterase activity by dibucaine

Answer

Gives percentage of lignocaine levels in blood

Answer

Gives percentage of metabolised lignocaine levels

Answer

Gives percentage of succinylcholine in blood

Question 3

HLA-B*5701 is an allele associated with hypersensitivity to abacavir. Which of the following is the parent allele of HLA-B*5701?

Accepted Answer

HLA-B*57

Answer

HLA-B*5

Answer

HLA-B*51

Answer

HLA-DQ2

Question 4

Hemolysis in G6PD deficiency is precipitated by all of the following except:

Accepted Answer

Penicillin

Answer

Cotrimoxazole

Answer

Quinine

Answer

Dapsone

Question 5

The risk of carbamazepine-induced Stevens-Johnson syndrome is increased in the presence of which of the following genes?

Accepted Answer

HLA-B* 1502

Answer

HLA-B* 5801

Answer

HLA-B* 5701

Answer

HLA-B*27

Question 6

Which of the following is not considered a pharmacogenetic condition?

Accepted Answer

Adenosine deaminase deficiency

Answer

Coumarin insensitivity

Answer

G6PD deficiency

Answer

Malignant hyperthermia

Pharmacogenomics — MCQs

Pharmacogenomics — MCQs

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