A rise in skin temperature results in increased percutaneous absorption.

• A. Increasing
• B. Decreased
• C. No effect
• D. Variable

Answer: (A)

Raising temperature speeds molecular motion, which makes diffusion through the skin easier. In percutaneous absorption, the rate is governed by how quickly the drug can diffuse through the stratum corneum and how well it partitions into the skin, plus the driving concentration gradient. Temperature increases the diffusion coefficient (D) and often improves drug partitioning into the skin, while also boosting skin blood flow that helps maintain the gradient by clearing drug away. Together, these effects raise the amount of drug that crosses the skin over a given time. So, as skin temperature goes up, percutaneous absorption generally increases. While extreme heat can disrupt the barrier, within typical physiological ranges the trend is clearly upward.