Which phase of pharmacokinetics is affected by the first pass effect?
Excretion
Metabolism
Distribution
Absorption
The Correct Answer is D
Choice A: Excretion
Excretion is the process by which drugs and their metabolites are eliminated from the body, primarily through the kidneys (urine), but also via bile, sweat, saliva, and other routes. While excretion is a crucial phase of pharmacokinetics, it is not directly impacted by the first pass effect. The first pass effect primarily involves the metabolism of a drug before it reaches systemic circulation, which occurs prior to the excretion phase.
Choice B: Metabolism
The first pass effect, also known as first-pass metabolism or presystemic metabolism, significantly impacts the metabolism phase of pharmacokinetics. This phenomenon occurs when a drug is metabolized at a specific location in the body, such as the liver or gut wall, before it reaches systemic circulation. As a result, the concentration of the active drug is reduced, affecting its bioavailability. The liver is the primary site for this metabolic process, where enzymes break down the drug, potentially leading to a significant reduction in its therapeutic effect.
Choice C: Distribution
Distribution refers to the process by which a drug is transported from the bloodstream to various tissues and organs in the body. This phase is influenced by factors such as blood flow, tissue permeability, and binding to plasma proteins. However, the first pass effect does not directly alter the distribution phase. Instead, it affects the amount of drug that enters systemic circulation, which in turn can influence the extent of distribution.
Choice D: Absorption
Absorption is the process by which a drug enters the bloodstream from its site of administration. This phase is crucial for determining the onset of a drug’s action. While the first pass effect occurs after absorption, it does not directly change the absorption phase itself. Instead, it affects the drug’s concentration after it has been absorbed and before it reaches systemic circulation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A Reason:
Clinical trials to assess the teratogenic effects of medications during pregnancy are ethically challenging because they would involve exposing pregnant women and their fetuses to potential risks. The primary concern is the safety of the fetus, as many drugs can cross the placenta and potentially cause harm. Therefore, most of the data on teratogenic effects come from observational studies, case reports, and animal studies rather than controlled clinical trials.
Choice B Reason:
While the FDA has initiatives to improve the safety of medications during pregnancy, it is not accurate to say that a new study will allow testing of medications during pregnancy in the future. The ethical concerns surrounding the exposure of pregnant women to potential teratogens remain a significant barrier. Current efforts focus on improving post-marketing surveillance and encouraging the reporting of adverse effects to gather more data.
Choice C Reason:
Although some women may be reluctant to admit taking medications during pregnancy, this is not the primary reason for the lack of data on teratogenic effects. The main issue is the ethical and practical challenges of conducting clinical trials in pregnant women. Reluctance to report medication use can contribute to underreporting, but it is not the central factor.
Choice D Reason:
Recommending that pregnant women avoid medications is a general precaution, but it does not address the reason why more is not known about teratogenic effects. The avoidance of medications is advised to minimize potential risks, but the lack of data is primarily due to the ethical constraints of conducting clinical trials in this population.
Correct Answer is B
Explanation
Choice A: Oncogene Activation
Oncogene activation refers to the process by which normal genes (proto-oncogenes) become oncogenes, leading to uncontrolled cell growth and potentially cancer. This process involves mutations or overexpression of genes that regulate cell proliferation and survival. While oncogene activation is a critical factor in cancer development, it is not directly related to hydropic swelling, which is a form of cellular injury characterized by the accumulation of water within cells.
Choice B: Sodium/Potassium Pump Dysfunction
Hydropic swelling, also known as cellular swelling, results from the malfunction of the sodium/potassium (Na+/K+) pump. This pump is essential for maintaining the ionic balance within cells by actively transporting sodium out of the cell and potassium into the cell. When the Na+/K+ pump fails, sodium accumulates inside the cell, leading to an influx of water to balance the osmotic pressure. This results in cellular swelling, which is a hallmark of reversible cell injury.
Choice C: Membrane Rupture
Membrane rupture refers to the breaking of the cell membrane, which can lead to cell death and the release of cellular contents into the surrounding tissue. This process is typically associated with irreversible cell injury and necrosis. While membrane rupture can result from severe cellular damage, it is not the primary cause of hydropic swelling, which occurs due to ionic imbalances rather than physical disruption of the cell membrane.
Choice D: ATP Accumulation
ATP (adenosine triphosphate) is the primary energy currency of the cell, used to power various cellular processes. Accumulation of ATP within the cell is not typically associated with cellular swelling. In fact, a decrease in ATP levels, rather than an accumulation, is more likely to contribute to cellular injury. Reduced ATP levels can impair the function of the Na+/K+ pump, leading to ionic imbalances and subsequent hydropic swelling.
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