Which of the following statements best describes the first-pass effect?
Medication that crosses the blood brain barrier.
Hepatocytes in the liver metabolize medication after absorption.
The bloodstream distributes medications throughout the body.
The kidneys excrete medications by way of urine production.
The Correct Answer is B
A. Medication that crosses the blood-brain barrier: The ability of a drug to cross the blood-brain barrier depends on its lipid solubility and molecular size, but this process is unrelated. The first-pass effect specifically involves hepatic metabolism, not central nervous system entry.
B. Hepatocytes in the liver metabolize medication after absorption: The first-pass effect occurs when orally administered drugs are absorbed through the gastrointestinal tract and transported to the liver via the portal vein. Hepatocytes metabolize part of the drug before it reaches systemic circulation, reducing its active concentration.
C. The bloodstream distributes medications throughout the body: Distribution refers to how a drug moves from systemic circulation into tissues and organs. This process occurs after the first-pass effect and is distinct from hepatic metabolism.
D. The kidneys excrete medications by way of urine production: Renal excretion is the primary mechanism of drug elimination, not metabolism. While important for drug clearance, it occurs after systemic circulation and is unrelated to the hepatic first-pass process.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. 8 hours: In 8 hours, four half-lives would have passed. Starting at 400 mg, the drug would decrease to 200 mg (2 hrs), 100 mg (4 hrs), 50 mg (6 hrs), and then 25 mg (8 hrs). At 8 hours, the level would be below 50 mg, not exactly 50 mg.
B. 4 hours: At 4 hours, two half-lives have passed. The concentration would decrease from 400 mg to 200 mg (2 hrs) and then to 100 mg (4 hrs). This is higher than the target concentration of 50 mg.
C. 6 hours: At 6 hours, three half-lives have passed. The drug concentration decreases from 400 mg to 200 mg (2 hrs), then to 100 mg (4 hrs), and finally to 50 mg (6 hrs). This matches the target level exactly.
D. 2 hours: After only one half-life, the concentration decreases from 400 mg to 200 mg. This is still much higher than 50 mg and does not reflect the correct timing for the required reduction.
Correct Answer is A
Explanation
A. The ability of a drug to produce a therapeutic effect: Efficacy refers to the maximum therapeutic response a drug can achieve, regardless of dose. It reflects the drug’s intrinsic ability to activate receptors or physiological pathways to produce the desired effect.
B. The time it takes to reach a therapeutic effect: This describes the onset of action, not efficacy. Onset refers to how quickly a drug begins to work after administration, which depends on absorption rate and route, not the drug’s inherent effectiveness.
C. The amount of drug required to produce an effect: This defines potency, not efficacy. Potency compares the dose needed to achieve a given effect, whereas efficacy focuses on the maximum effect achievable once all receptors are activated.
D. The highest serum concentration of a drug: This represents peak concentration, the point when the drug level in plasma is at its maximum. It does not indicate the magnitude of therapeutic response, which is the focus of efficacy.
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