Which of the curves best depicts the log dose-response curve of that agonist when a fixed dose of a competitive α antagonist is given concomitantly?

Correct Answer: B

Rationale: In pharmacology, understanding dose-response curves is crucial for predicting drug effects. When a fixed dose of a competitive α antagonist is given concomitantly with an agonist, it will shift the dose-response curve to the right due to competitive inhibition. Option B is the correct choice because it represents a rightward shift in the dose-response curve, indicating competitive antagonism. This shift means higher doses of the agonist are needed to produce the same effect in the presence of the antagonist. Options A, C, and D can be eliminated because they do not show the characteristic rightward shift seen with competitive antagonists. Curve P (A) may indicate a non-competitive antagonist, while Curves R (C) and S (D) do not demonstrate any form of antagonism. Educationally, this question reinforces the concept of competitive antagonism and how it influences dose-response relationships. Understanding these principles is essential for predicting drug interactions and designing effective treatment regimens in clinical practice.

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: A

Rationale: Infliximab, a monoclonal antibody used to treat rheumatoid arthritis, primarily distributes to fat tissue. This distribution pattern is due to the large molecular size of infliximab, which limits its movement across cell membranes and into other compartments. Within fat tissue, infliximab can be stored for extended periods, leading to a prolonged duration of action. Option A is correct because infliximab's high molecular weight and hydrophobic nature favor its accumulation in adipose tissue. This storage allows for a slow release of the drug into the bloodstream, contributing to its long half-life and sustained therapeutic effect. Options B, C, and D are incorrect: - Plasma (Option B) is where most small molecules and protein-bound drugs distribute, not large molecules like infliximab. - Extracellular fluids (Option C) are more relevant for smaller molecules with good water solubility, not for large proteins like infliximab. - Cell cytosol (Option D) is typically reserved for intracellular drug targets or small, lipophilic molecules that can penetrate cell membranes easily, which is not the case for infliximab. Understanding the distribution of drugs like infliximab is crucial in pharmacology as it impacts dosing, duration of action, and potential side effects. Students studying pharmacology need to grasp these concepts to make informed decisions when prescribing medications to patients.

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.