Hyperpigmented skin results in what effect on percutaneous penetration?

• A. Increased
• B. Decreased
• C. No change
• D. Unpredictable

Answer: (B)

The amount of drug that penetrates the skin depends largely on the barrier properties of the outermost layer, the stratum corneum. When skin is hyperpigmented, there is typically more melanin in the epidermis and often some thickening or heightened keratinization of the epidermis. Melanin can bind certain drugs and effectively trap them in the upper layers, while a thicker, more keratinized stratum corneum presents a tougher barrier for diffusion. Both factors tend to slow or limit the rate at which a drug can move into or through the skin, leading to decreased percutaneous penetration.