The particle size of the dispersed solid in a suspension is usually greater than

Correct Answer: A

Rationale: The particle size of the dispersed solid in a suspension is usually greater than 0.5 μm (A). Suspensions are heterogeneous systems with insoluble particles large enough to settle (e.g., oral antacids), distinguishing them from colloids (0.001-0.5 μm). Options B (0.4 μm), C (0.3 μm), and D (0.2 μm) fall below this threshold, while 0.1 μm (original E) is even smaller. This size ensures visible dispersion, requiring shaking before use, and impacts stability and bioavailability, as larger particles dissolve slower, a key consideration in pharmaceutical suspensions.

Correct Answer: C

Rationale: Cellulose acetate phthalate (C) is used to coat enteric tablets, dissolving above pH 6 (intestine), protecting drugs (e.g., aspirin) from gastric acid. Hydroxypropyl methyl cellulose (A) and carboxymethyl cellulose (B) are film-formers, not enteric-specific. No option D or original E exists. This pH-dependent coating delays release, reducing gastric irritation or degradation, critical for targeted delivery and efficacy in oral formulations, leveraging gastrointestinal pH gradients.

Correct Answer: D

Rationale: Simple diffusion (D) is the passage of drug molecules from high to low concentration, a passive process driven by the gradient (e.g., ethanol across membranes), requiring no energy. Active transport (A) uses energy against the gradient. Bioavailability (B) is the fraction reaching systemic circulation. Biopharmaceutics (C) studies formulation effects. Pinocytosis (original E) involves vesicular uptake. Diffusion's lipid solubility dependence governs most drug absorption, a fundamental principle in pharmacokinetics, impacting onset and distribution rates.

Correct Answer: B

Rationale: Nonlinear pharmacokinetics feature an elimination half-life (t_½) that increases as the dose increases (B), as elimination (e.g., via saturable enzymes) becomes zero-order (e.g., phenytoin), prolonging clearance at high doses. Option A is false; metabolite ratios change with saturation. Option C is incorrect; AUC rises disproportionately. Option D is wrong; high doses shift from first-order. Option E (original) about steady-state is first-order-specific. This saturation alters dosing (e.g., phenytoin monitoring), critical to avoid toxicity in nonlinear drugs.

Correct Answer: D

Rationale: The principle of superposition assumes early doses do not affect subsequent doses (D), valid in first-order kinetics where each dose's elimination is independent, summing linearly to predict steady-state (e.g., amoxicillin). Option A suggests nonlinearity (e.g., phenytoin). Option B is zero-order (e.g., ethanol). Option C overestimates; steady-state is ~4-5 half-lives. Option E (original) is unrelated. This linearity simplifies multiple-dose design, ensuring predictable accumulation, critical for maintaining therapeutic levels without toxicity.