This patient's disease was most likely mediated by genetic polymorphism of which of the following enzymes?

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.

Correct Answer: B

Rationale: The large first-pass effect most likely affected the oral bioavailability of the drug. First-pass effect refers to the metabolism of a drug before it reaches systemic circulation, reducing the amount of drug available for action. This would impact the drug's bioavailability when administered orally.

Correct Answer: D

Rationale: In pharmacology, understanding the factors that regulate the relationship between drug concentration and drug-receptor complex formation is crucial for predicting drug effects. The correct answer, option D - The law of mass action, is based on the fundamental principle that the rate of a chemical reaction is directly proportional to the product of the concentrations of the reacting substances. In the context of drug-receptor interactions, this law explains how the concentration of a drug and its binding to a receptor influence the formation of drug-receptor complexes, ultimately affecting the pharmacological response. Option A, the pharmacological response, does not directly regulate the relationship between drug concentration and drug-receptor complex formation but rather is the outcome of this interaction. Option B, the volume of distribution of the drug, and option C, the total clearance of the drug, are important pharmacokinetic parameters but do not specifically address the relationship between drug concentration and receptor binding. Understanding the law of mass action in pharmacology provides a foundational concept for predicting and understanding drug interactions, efficacy, and potential side effects. It serves as a basis for dose-response relationships and therapeutic drug monitoring, essential aspects of pharmacotherapy. By grasping this principle, students can better comprehend how drugs exert their effects at the molecular level, leading to more informed and effective clinical decision-making.

Correct Answer: B

Rationale: In this scenario, option B, "The presence of strong pain," is the correct answer that most likely delayed the oral absorption of acetaminophen in the patient who took a large dose in aqueous solution. Strong pain can lead to decreased gastrointestinal motility due to the activation of the sympathetic nervous system, which can slow down the absorption of drugs like acetaminophen. This delayed absorption occurs because the body's focus shifts to managing the pain rather than digesting and absorbing the medication efficiently. Now, let's analyze why the other options are incorrect: A) A moderate increase in intestinal peristalsis: Increased peristalsis would actually enhance drug absorption by moving the drug through the gastrointestinal tract more quickly, rather than delaying it. C) The administration of the drug in aqueous solution: The drug being in an aqueous solution would not inherently delay absorption. In fact, many drugs are administered in this form to aid in quicker absorption. D) A large volume of distribution of the drug: The volume of distribution is related to the drug's distribution in the body's compartments and not directly linked to oral absorption delays. Educational Context: Understanding factors that can influence drug absorption is crucial in pharmacology. Students need to grasp how physiological conditions like pain can impact drug pharmacokinetics. This knowledge is vital for healthcare professionals to make informed decisions about medication administration based on individual patient factors.

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.