Which of the following terms best describes a drug that blocks the action of epinephrine at its receptors by occupying those receptors without activating them?

Correct Answer: A

Rationale: A pharmacological antagonist (A) best describes a drug that blocks epinephrine's action by occupying its receptors (e.g., beta-blockers like propranolol) without activation, competitively inhibiting the agonist. Partial agonists (B) activate receptors submaximally (e.g., pindolol). Physiological antagonists (C) counteract via different systems (e.g., histamine vs. epinephrine). Chemical antagonists (D) bind the agonist itself (e.g., chelators), not receptors. Noncompetitive antagonists (original E) bind irreversibly, reducing receptor availability. Pharmacological antagonism, central to receptor theory, relies on affinity without efficacy, reversing or preventing epinephrine's effects (e.g., tachycardia), a key concept in managing adrenergic overactivity in conditions like hypertension.

Correct Answer: C

Rationale: Most drug receptors are proteins located on cell membranes or in the cytosol (C), such as G-protein-coupled receptors (e.g., beta-adrenergic) or intracellular nuclear receptors (e.g., steroid receptors), mediating specific drug effects. Small molecules (A) like neurotransmitters aren't receptors. Lipids (B) form membranes, not receptors. DNA (D) and RNA (original E) are targets for some drugs (e.g., chemotherapy), not typical receptors. Proteins' structural diversity enables ligand binding and signal transduction, fundamental to pharmacodynamics, distinguishing receptor-mediated effects from non-specific actions like osmosis.

Correct Answer: C

Rationale: The Arrhenius equation (C), k = Ae^(-Ea/RT), predicts drug stability at room temperature by relating reaction rate (k) to temperature (T), using activation energy (Ea) from accelerated studies (e.g., 40°C). Stokes (A) addresses viscosity, Yong (B) is undefined here, Michaelis-Menten (D) is enzyme kinetics, and Hixson-Crowell (original E) models dissolution. This exponential relationship extrapolates shelf life (e.g., 25°C) from higher-temperature degradation rates, critical in pharmaceutical development for ensuring potency and safety over time.

Correct Answer: A

Rationale: Mineral oil (A) is most likely used to lubricate molds in the fusion method for cocoa butter suppositories, preventing sticking and ensuring easy release post-cooling. Propylene glycol (B) is a humectant, not a lubricant. Cetyl alcohol (C) and stearic acid (D) are base components, not mold lubricants. Magnesium silicate (original E) is a filler, not suitable. Mineral oil's inert, oily nature facilitates clean suppository production, maintaining shape and drug uniformity (e.g., bisacodyl), a practical step in extemporaneous compounding.

Correct Answer: C

Rationale: A ceramic mortar is preferable when comminution is desired in addition to mixing (C), its rough surface grinding particles effectively (e.g., reducing tablet fragments), unlike smooth glass. Volatile oils (A) risk loss regardless of mortar. Dyes (B) stain ceramics, favoring glass. No option D or original E exists. Ceramic's abrasive texture enhances particle size reduction, critical in extemporaneous compounding for uniform powders, improving dissolution and bioavailability in solid dosage forms.