Nokea
A 59-year-old Japanese man with atrial fibrillation presented to his physician complaining of red urine. The man had been receiving a standard dose of warfarin, which is an anticoagulant drug biotransformed by CYP2C9 isozyme. Which of the following was the most likely cause of the patient's disorder?
- A. Increased protein binding of warfarin
- B. Decreased renal excretion of warfarin
- C. Genetic polymorphism of CYP2C9
- D. Decreased metabolism of CYP2C9
Correct Answer: C
Rationale: The most likely cause of the patient's disorder is a genetic polymorphism of CYP2C9. Genetic polymorphisms can affect the metabolism of drugs, including warfarin, leading to variations in drug response and potential adverse effects. In this case, the patient's red urine may be a result of altered metabolism of warfarin due to genetic variations in the CYP2C9 isozyme, which plays a key role in the biotransformation of the drug. This can result in increased levels of unmetabolized warfarin in the body, potentially leading to adverse effects such as red urine.
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A new drug was tested in an in vitro system. It was found that only one enantiomer of the racemic pair bound substantially to a specific receptor, whereas the other enantiomer showed negligible binding. Which of the following terms best defines this property?
- A. Stereoselectivity
- B. Intrinsic activity
- C. Affinity
- D. Potency
Correct Answer: A
Rationale: Stereoselectivity refers to the phenomenon where one enantiomer of a racemic pair exhibits a significantly different interaction compared to the other enantiomer. In this case, the enantiomer that binds substantially to the receptor while the other does not demonstrates stereoselectivity. The term "intrinsic activity" refers to the ability of a drug to activate a receptor, "affinity" refers to the strength of binding between a drug and its receptor, and "potency" refers to the concentration of a drug required to produce a specific effect. Therefore, the correct answer is A.
The nurse is explaining drug action to a nursing student. Which statement made by the nurse is correct?
- A. Water-soluble and ionized drugs are quickly absorbed
- B. A drug not bound to protein is an active drug.
- C. Most receptors are found under the cell membran
- D. Toxic effects can result if the trough level is low.
Correct Answer: B
Rationale: B: A drug not bound to protein is an active drug.
Rationale: Protein-bound drugs are inactive as they cannot reach target sites. When unbound, drugs can exert pharmacological effects. This is known as the free drug hypothesis. The statement correctly highlights the importance of drug binding to proteins in affecting drug action.
Summary:
A: Water-soluble and ionized drugs are slow to be absorbed due to their inability to cross membranes easily.
C: Receptors are found on the cell membrane, not under it. This statement is inaccurate.
D: Toxic effects are more likely to occur with high trough levels, not low levels.
An agonist activates a receptor and stimulates a response. When given frequently over time the body may:
- A. Up-regulate the total number of receptors
- B. Block the receptor with a partial agonist
- C. Alter the drug’s metabolism
- D. Down-regulate the numbers of that specific receptor
Correct Answer: D
Rationale: The correct answer is D: Down-regulate the numbers of that specific receptor.
Step 1: When an agonist continuously activates a receptor, the body may reduce the number of receptors to maintain homeostasis.
Step 2: Down-regulation is a feedback mechanism to decrease receptor sensitivity due to excessive stimulation.
Step 3: This helps prevent overstimulation and desensitization of the receptor.
Summary:
A: Up-regulating the total number of receptors is unlikely as the body typically down-regulates in response to prolonged agonist exposure.
B: Blocking the receptor with a partial agonist is not a typical response to repeated agonist exposure.
C: Altering the drug's metabolism is not directly related to receptor down-regulation in response to agonist stimulation.
The nurse educator on the unit receives a list of high- alert drugs. Which strategy is recommended to decrease the risk of errors? (Select all that apply.)
- A. Store drugs on a shelf for quick retrieval.
- B. Limit access to high-alert drugs.
- C. Use special labels for high-alert drugs.
- D. Provide increased training to staff.
Correct Answer: B
Rationale: The correct answer is B: Limit access to high-alert drugs. This strategy is recommended to decrease the risk of errors because it restricts the availability of high-risk medications to only authorized personnel, reducing the likelihood of medication errors. By limiting access, only trained and qualified staff members will handle these drugs, minimizing the potential for mistakes.
Explanation for other choices:
A: Storing drugs on a shelf for quick retrieval may increase the risk of errors as it allows easier access to high-alert drugs, potentially leading to misuse or incorrect administration.
C: Using special labels for high-alert drugs can be helpful but may not be as effective as limiting access in preventing errors.
D: Providing increased training to staff is beneficial, but alone may not be sufficient to reduce errors if access to high-alert drugs is not restricted.
This patient's disease was most likely mediated by genetic polymorphism of which of the following enzymes?
- A. N-acetyltransferase
- B. Glucose-6-phosphate dehydrogenase
- C. Reduced form of nicotinamide adenine dinucleotide (NADH)-methemoglobin reductase
- D. Pseudocholinesterase
Correct Answer: B
Rationale: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is associated with hemolytic anemia triggered by certain drugs like chloroquine. The patient's presentation with hemolytic anemia after chloroquine treatment suggests a G6PD deficiency, making it the most likely enzyme involved in this patient's disease.