A 22-year-old woman suffering from asthma was prescribed albuterol by inhalation. Albuterol is a bronchodilating drug with a molecular weight of 239 daltons. Which of the following permeation processes most likely accounted for the transfer of the drug through the bronchial mucosa?

Correct Answer: B

Rationale: Lipid diffusion is the most likely permeation process for the transfer of albuterol through the bronchial mucosa. Lipid-soluble molecules like albuterol can easily pass through the lipid bilayer of cell membranes. The other options are less likely mechanisms for the absorption of albuterol in this context.

Correct Answer: C

Rationale: The correct answer is C. Stereoselectivity refers to the phenomenon where one enantiomer of a drug has a significantly higher binding affinity to a receptor compared to its mirror-image enantiomer. In this scenario, one enantiomer binds substantially while the other shows negligible binding, indicating stereoselectivity in receptor binding. This property is crucial in drug development as it can impact the efficacy and safety profile of a medication. Intrinsic activity (choice A) refers to the ability of a drug to activate a receptor once bound, while affinity (choice B) is the strength of binding between a drug and its receptor. Potency (choice D) refers to the dose of a drug required to produce a specific effect, and variability (choice E) is the degree of inconsistency in response to a drug.

Correct Answer: B

Rationale: In pharmacology, understanding drug interactions is crucial to ensure patient safety and effective treatment outcomes. In this scenario, the cimetidine-diazepam interaction in the 46-year-old woman is best defined as potentiation, which is option B. Potentiation occurs when the effect of one drug is increased by another drug without a direct pharmacological interaction. Cimetidine, a histamine H2 receptor antagonist, inhibits the metabolism of diazepam, a benzodiazepine, leading to increased diazepam levels in the body. This can result in enhanced sedative effects and potential toxicity. Option A, synergism, refers to a combined effect of two drugs being greater than the sum of their individual effects through a shared mechanism of action, which is not the case in this scenario. Option C, additive, implies a combined effect that is simply the sum of the individual effects, which does not accurately describe the cimetidine-diazepam interaction. Option D, antagonism, suggests one drug diminishing the effect of another, which is not the case here. Educationally, this question highlights the importance of recognizing different types of drug interactions and their implications in clinical practice. Understanding how drugs can interact helps healthcare professionals make informed decisions, prevent adverse reactions, and optimize therapeutic outcomes for patients. It underscores the significance of considering pharmacokinetic and pharmacodynamic factors when prescribing medications, especially in cases where interactions can potentiate or diminish drug effects.

Correct Answer: A

Rationale: Infliximab, as a monoclonal antibody, is a large molecule that is more likely to distribute to tissues like fat due to their ability to store and release drugs slowly. Fat tissue is a common site of distribution for large molecules and lipophilic drugs. Therefore, fat tissue is the most likely main site of distribution for infliximab.

Correct Answer: D

Rationale: In the context of pharmacology, understanding the factors that regulate the relationship between drug concentration and drug-receptor complex association and dissociation is crucial for effective drug therapy. The correct answer, D) The law of mass action, is based on the principle that the rate of a chemical reaction is directly proportional to the product of the concentrations of the reactants. In the case of drug-receptor interactions, the law of mass action governs the equilibrium between drug molecules and their respective receptors. Option A) The pharmacological response is incorrect because it refers to the observable effects of a drug on the body, which are downstream events influenced by the drug-receptor interaction but not directly regulating it. Option B) The volume of distribution of the drug is a pharmacokinetic parameter that describes the extent of drug distribution in the body, not directly regulating the drug-receptor complex formation. Option C) The total clearance of the drug is a pharmacokinetic parameter that describes the overall removal of a drug from the body over time, which does not specifically regulate the drug-receptor binding dynamics. Understanding the law of mass action in drug-receptor interactions provides a foundational basis for predicting and optimizing drug efficacy and safety in clinical practice. By grasping this fundamental concept, healthcare professionals can make informed decisions regarding drug dosing, drug interactions, and treatment outcomes.