Which statement best distinguishes loading dose from maintenance dose?

• A. Loading dose is smaller than maintenance dose.
• B. Loading dose is given after maintenance dose to prevent accumulation.
• C. Loading dose rapidly achieves target concentration (often Css); maintenance dose sustains it with interval dosing.
• D. Loading dose is only used for oral dosing.

Answer: (C)

The main idea is that a loading dose is used to reach the target drug concentration quickly, while the maintenance dose keeps that level steady with regular dosing. A loading dose delivers enough drug to fill the body’s volume of distribution rapidly, so the concentration moves toward the target (often the steady-state) quickly. Once that level is reached, maintenance dosing continues at intervals to replace what’s lost to clearance, keeping the concentration in the desired range. This is captured by the relationships: loading dose = Css × Vd and maintenance dose rate = Css × Cl. That’s why the statement describing rapid attainment of the target concentration and subsequent maintenance with interval dosing is the best fit. The other ideas don’t fit because the loading dose isn’t universally smaller than maintenance, it isn’t given after maintenance to prevent accumulation, and loading doses aren’t restricted to oral dosing.