The nurse assesses a patient who takes ibuprofen [Advil] on a regular basis. Which finding would indicate a severe adverse effect of ibuprofen therapy?

Choice A reason: A 25-year-old man typically has mature liver and kidney function, efficiently metabolizing and excreting CNS depressants like benzodiazepines. Toxicity risk is lower compared to neonates, whose immature systems impair drug clearance, making this choice less critical for close toxicity monitoring.

Choice B reason: A 15-year-old boy has relatively mature metabolic pathways, though not fully adult-like. CNS depressants are cleared more effectively than in neonates, reducing toxicity risk. Adolescents are less vulnerable than infants to accumulation, making this choice less concerning for drug toxicity observation.

Choice C reason: A 3-week-old neonate has immature liver enzymes (e.g., CYP450) and reduced renal clearance, increasing the risk of CNS depressant toxicity (e.g., respiratory depression, sedation). Their low body mass and underdeveloped metabolism necessitate close monitoring, making this the correct choice for heightened toxicity vigilance.

Choice D reason: A 25-year-old woman, like men of the same age, typically has efficient drug metabolism and excretion. CNS depressants pose lower toxicity risk compared to neonates, whose immature systems lead to drug accumulation, making this choice less critical for close toxicity monitoring.

Choice A reason: Synthesis of more receptor sites (upregulation) typically occurs with receptor antagonists, not agonists, as the body compensates for blocked receptors. This would increase drug sensitivity, not decrease effectiveness. For most medications, continuous exposure leads to desensitization, not receptor proliferation, making this choice incorrect for explaining tolerance.

Choice B reason: Decreased receptor selectivity implies a drug binding to unintended receptors, causing varied effects, not reduced efficacy. Tolerance results from receptor desensitization, not altered selectivity. This mechanism doesn’t explain the patient’s “immunity” to the drug’s therapeutic effects, making this choice scientifically inaccurate for the scenario.

Choice C reason: Desensitization occurs when continuous drug exposure reduces receptor responsiveness, leading to tolerance. For example, opioid receptors downregulate or internalize with prolonged agonist exposure, decreasing drug efficacy. This explains the patient’s perception of “immunity” as the drug’s effect diminishes over time, making this the correct choice.

Choice D reason: The body does not produce antagonists to compete with drugs for receptor sites. Tolerance arises from receptor desensitization or metabolic changes (e.g., enzyme induction), not endogenous antagonist production. This mechanism is not a recognized pharmacological process for reduced drug effectiveness, making this choice incorrect.