Which of the following terms best defines the tested drug?

Correct Answer: A

Rationale: The tested drug is best defined as a noncompetitive antagonist, which binds irreversibly to the receptor site and prevents the activation of the receptor by the endogenous ligand. This property distinguishes noncompetitive antagonists from other types of drugs and is important in understanding their mechanism of action and therapeutic effects.

Correct Answer: D

Rationale: The coma caused by thio- pental is most likely due to a pseudoallergic reaction, as this type of reaction can lead to severe symptoms such as seizures and coma. Pseudoallergic reactions are non-immunologic reactions that can occur in individuals even without prior exposure to the drug, making them unpredictable and potentially life-threatening. In this case, the patient's history of acute intermittent porphyria may have contributed to the pseudoallergic reaction to thio- pental.

Correct Answer: B

Rationale: In pharmacology, bioavailability refers to the proportion of a drug that reaches systemic circulation following administration. The correct answer, Drug Q, likely has the highest oral bioavailability among the options due to its specific pharmacokinetic properties. Drug Q might have a higher oral bioavailability because of factors such as better absorption, minimal first-pass metabolism, or formulation enhancements that improve its uptake in the gastrointestinal tract. This could lead to a higher concentration of the drug in the bloodstream after oral administration compared to the other options. Conversely, Drugs P, R, and S may have lower oral bioavailability for various reasons. Drug P might have poor absorption, Drug R could undergo significant first-pass metabolism reducing its systemic availability, and Drug S might have formulation issues that hinder its absorption. Educationally, understanding factors influencing oral bioavailability is crucial for pharmacology students and healthcare professionals to optimize drug therapy outcomes. It highlights the importance of drug formulation, pharmacokinetics, and patient-specific factors in drug selection and dosing. Remembering these principles aids in selecting appropriate medications for patients based on their individual needs and characteristics.

Correct Answer: B

Rationale: Lipid solubility of a drug is influenced by its pKa value. Since valproic acid has a pKa of 5, it would likely be lipid soluble at a pH of 7 in the duodenal lumen. The Henderson-Hasselbalch equation suggests that when the pH is higher than the pKa, the drug will predominantly be in its non-ionized, lipid-soluble form. In this case, the drug would be about 24% lipid soluble in the duodenal lumen, making choice B the correct answer.

Correct Answer: D

Rationale: The injected dose of cocaine can be calculated using the formula Dose = Cp * Vd, where Cp is the plasma concentration, and Vd is the volume of distribution. Given that the plasma level of cocaine was 0.75 mg/L, and the volume of distribution is about 130 L, the injected dose can be calculated as 0.75 * 130 = 97.5 mg, which is closest to option D.