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Questions and Answers
What do genetic polymorphisms in Phase I enzymes result in?
What do genetic polymorphisms in Phase I enzymes result in?
- Altered drug efficacy and safety
- Patients who biotransform many drugs at different rates (correct)
- Increased enzyme activity for all drugs
- Universal drug response among all patients
What drug does the CYP 2D6 enzyme convert codeine into?
What drug does the CYP 2D6 enzyme convert codeine into?
- Heroin
- Morphine (correct)
- Oxycodone
- Fentanyl
What is codeine?
What is codeine?
- An opioid analgesic
- A stimulant
- An anti-inflammatory drug
- A prodrug (correct)
What is the most common form of genetic polymorphism?
What is the most common form of genetic polymorphism?
Which polymorphisms receive the least benefit from codeine?
Which polymorphisms receive the least benefit from codeine?
Is Thiopurine-S-methyltransferase (TPMT) a Phase I or Phase II enzyme?
Is Thiopurine-S-methyltransferase (TPMT) a Phase I or Phase II enzyme?
What drugs does Thiopurine-S-methyltransferase (TPMT) deactivate?
What drugs does Thiopurine-S-methyltransferase (TPMT) deactivate?
Which of the following is a thiopurine drug used to suppress the immune system that may result in bone marrow suppression and loss of blood cell production?
Which of the following is a thiopurine drug used to suppress the immune system that may result in bone marrow suppression and loss of blood cell production?
What percentage of Europeans are intermediate metabolizers (IMs) for TPMT?
What percentage of Europeans are intermediate metabolizers (IMs) for TPMT?
What percentage of Europeans have low to no TPMT activity?
What percentage of Europeans have low to no TPMT activity?
What should be done when someone is an intermediate metabolizer (IM) for thiopurine methyltransferase (TPMT)?
What should be done when someone is an intermediate metabolizer (IM) for thiopurine methyltransferase (TPMT)?
What can happen to patients who have low or no TPMT activity?
What can happen to patients who have low or no TPMT activity?
Match each enzyme/ system to its associated drug
Match each enzyme/ system to its associated drug
What can sulfamethoxazole cause in people who have decreased G6P?
What can sulfamethoxazole cause in people who have decreased G6P?
Why can succinylcholine be problematic?
Why can succinylcholine be problematic?
Why does abacavir cause adverse drug reactions in HIV patients?
Why does abacavir cause adverse drug reactions in HIV patients?
For which drug were ADRs considered idiosyncratic before further discoveries?
For which drug were ADRs considered idiosyncratic before further discoveries?
What is the role of Vitamin K Epoxidase reductase (VKORC1)?
What is the role of Vitamin K Epoxidase reductase (VKORC1)?
What happens with a polymorphism in Vitamin K Epoxidase reductase (VKORC1)?
What happens with a polymorphism in Vitamin K Epoxidase reductase (VKORC1)?
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Study Notes
Genetic Polymorphisms in Phase I Enzymes
- Genetic polymorphisms in Phase I enzymes can result in altered drug metabolism, leading to variations in drug efficacy and adverse drug reactions (ADRs).
CYP 2D6 Enzyme
- The CYP 2D6 enzyme converts codeine into morphine.
- Codeine is an opioid analgesic often used for pain relief.
Common Forms of Genetic Polymorphism
- The most common form of genetic polymorphism is single nucleotide polymorphisms (SNPs).
Polymorphisms and Codeine Benefit
- Individuals with certain polymorphisms in CYP2D6 may receive less benefit from codeine.
Thiopurine-S-methyltransferase (TPMT)
- Thiopurine-S-methyltransferase (TPMT) is a Phase II enzyme involved in the detoxification of thiopurine drugs.
- TPMT deactivates thiopurine drugs like azathioprine and 6-mercaptopurine.
Thiopurine Drugs
- Azathioprine is a thiopurine drug used to suppress the immune system.
- Azathioprine may cause bone marrow suppression and loss of blood cell production.
Intermediate Metabolizers (IMs) for TPMT
- Approximately 10% of Europeans are intermediate metabolizers (IMs) for TPMT.
- About 0.3% of Europeans have low to no TPMT activity.
TPMT Intermediate Metabolizer Recommendations
- Individuals who are intermediate metabolizers (IMs) for thiopurine methyltransferase (TPMT) require reduced doses of thiopurine drugs to prevent toxicity.
TPMT Deficiency
- Individuals with low or no TPMT activity may experience severe toxicity from thiopurine drugs.
Enzyme/System and Associated Drug Matches
- CYP2D6 - codeine
- TPMT - azathioprine
- Glucose-6-Phosphate Dehydrogenase (G6PD) - sulfamethoxazole
- Butyrylcholinesterase - succinylcholine
- HLA-B*5701 - abacavir
- Vitamin K Epoxidase Reductase (VKORC1) - warfarin
Adverse Drug Reactions (ADRs)
- Sulfamethoxazole can cause hemolytic anemia in individuals with decreased G6PD activity.
- Succinylcholine can cause prolonged muscle paralysis in individuals with genetic variations in butyrylcholinesterase.
- Abacavir causes adverse drug reactions in HIV patients with the HLA-B*5701 gene.
- ADRs associated with abacavir were initially considered idiosyncratic before further discoveries.
Vitamin K Epoxidase Reductase (VKORC1)
- Vitamin K Epoxidase reductase (VKORC1) plays a key role in the metabolism of warfarin.
- Polymorphisms in VKORC1 can lead to variations in warfarin responsiveness, necessitating precise dose adjustments.
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