Dose-response curves are used for drug evaluation in the animal laboratory and in the clinic, Quantal dose-response curves are often

Correct Answer: A

Rationale: Quantal dose-response curves are often used for determining the therapeutic index of a drug (A), the ratio of TD50 (toxic dose in 50% of subjects) to ED50 (effective dose in 50%), assessing safety (e.g., penicillin's high TI). Option B is incorrect; maximal efficacy is derived from graded curves, measuring continuous responses (e.g., blood pressure). Option C is false; inhibitors shift curves (e.g., rightward with competitive antagonists) but don't invalidate them. Option D is wrong; quantal curves apply to both intact subjects and tissues (e.g., lethality studies). Option E (original) about statistical variation fits graded curves better. Quantal curves, plotting all-or-none responses (e.g., survival), are key in toxicology and clinical trials for balancing efficacy and toxicity.

Correct Answer: A

Rationale: Heparin and protamine (A) is a good example of chemical antagonism, where protamine, a positively charged protein, binds and neutralizes negatively charged heparin, reversing its anticoagulant effect without receptor interaction. Protamine and zinc (B) form insulin complexes, not antagonism. Heparin and prothrombin (C) interact indirectly via clotting factors, not chemical binding. Option D is incorrect. This direct physicochemical interaction, distinct from receptor-based antagonism, is clinically vital in heparin overdose, rapidly restoring coagulation, showcasing a unique pharmacokinetic intervention.

Correct Answer: B

Rationale: Osmotic pressure (B) is a colligative property, depending on the number of solute particles in solution, not their identity (e.g., NaCl in IV fluids). Solubility (A) is a chemical property, varying with solute type. H⁺ concentration (C) defines pH, not colligative. Dissociation (D) affects particle number but isn't the property itself. Miscibility (original E) is unrelated. Colligative properties (osmotic pressure, boiling/freezing point changes) are critical in pharmacokinetics, influencing drug formulation and tonicity, ensuring compatibility with biological fluids.

Correct Answer: C

Rationale: Levigation reduces particle size (C) in suspension preparation, mixing a solid with a levigating agent (e.g., glycerin) to form a smooth paste, improving uniformity and dispersion (e.g., zinc oxide suspensions). Reducing zeta potential (A) stabilizes colloids, not levigation's goal. Avoiding bacterial growth (B) requires preservatives, not levigation. Enhancing viscosity (D) or reducing it (original E) isn't the aim; particle size is. This wet-grinding technique ensures palatability and consistent dosing in extemporaneous compounding, critical for patient acceptance and efficacy.

Correct Answer: A

Rationale: Waxed paper (A) best protects hygroscopic powders (e.g., sodium chloride), its water-resistant coating preventing moisture absorption. Glassine (B) is grease-resistant, less moisture-proof. White bond (C) and blue bond (D) are absorbent, unsuitable. Vegetable parchment (original E) offers some resistance but less than wax. This barrier property maintains powder stability, critical in dispensing hygroscopic drugs, preventing clumping or degradation, ensuring accurate dosing and shelf life in humid conditions.