Which of the following was most likely the oral bioavailability of the drug?

Correct Answer: D

Rationale: The oral bioavailability of a drug can be calculated using the formula F = AUC oral / AUC IV, where AUC is the area under the concentration-time curve. In this case, we are given the volume of distribution as 100 L and the theoretical plasma concentration at time 0 as 1 mg/L after oral administration of 200 mg. By calculating the AUC for both oral and IV routes, we can determine that the oral bioavailability is 1.0, which corresponds to option D.

Correct Answer: B

Rationale: Pharmacodynamic tolerance refers to the body's ability to adapt to the effects of a drug, leading to decreased responsiveness. In this case, the boy's ability to better tolerate alcohol effects indicates a form of tolerance mediated by homeostatic adaptive changes that counteract the drug effect. This type of tolerance involves physiological adjustments to mitigate the impact of the drug, allowing the individual to withstand higher doses. Therefore, the correct answer is B.

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.