Which statement about topical administration is correct?

• A. Fast onset and high control
• B. Immediate effect
• C. Variable onset
• D. Slow onset and poor control

Answer: (D)

Topical administration delivers the drug to a surface site with the goal of local effect, but it must cross tissue barriers and compete with saliva, mucus, and tissue turnover to reach its target. Because absorption depends on many local factors and the formulation, the onset of action is usually slower and the amount that actually reaches the target is less predictable compared with injections or systemic routes. That variability in absorption and diffusion makes the control over the drug’s effect less precise, which is why slow onset with poorer control is the most accurate general description of topical administration. While some topical products can have rapid effects in specific situations, the overall pattern in topical delivery tends to be slower and more variable than routes designed for immediate or tightly controlled systemic absorption.