|
 Dr. Lee is the founder and owner of Regrowth LLC, a company based in Los Angeles and dedicated to the treatment of hair loss. He has been developing innovative products and treating hair loss sufferers for the past 16 years. Dr. Lee is the creator of the Xandrox line of hair loss treatments.
Important Note: Due a busy schedule, Dr. Lee cannot answer any new questions at this time; however, he will be providing high quality answers to questions he receives from his own practice exclusively to Morphollica.com regularly
[name not provided]
2004-08-02
Absorption of medications into scalp
What are some of the factors involved in the percutaneous absorption of medications into the scalp?
For any drug to be effective topically, it must be formulated at the proper concentration and in the proper vehicle. The stratum corneum, the outermost layer of skin with a thickness of 0.010-0.020mm, is considered to be the rate-limiting barrier to percutaneous absorption. Although permeation of medications through the stratum corneum occurs primarily through the intercellular spaces, there is also diffusion through the adjacent cell membranes. Since the stratum corneum is not a living tissue, diffusion of medications through this layer is simply a passive process. Hydration of the stratum corneum increases its permeability to most types of drugs. A rise in the skin temperature can increase drug diffusion, because the diffusion constant is directly proportional to temperature. But, because the stratum corneum itself is a poor heat insulator and usually reflects the temperature of the environment, the temperature of the scalp remains fairly constant. The use of occlusive dressings causes only a small increase in temperature. Any increase in drug permeability due to occlusive dressing is primarily due to the increased hydration of the stratum corneum.
The hair follicles and sweat glands are sites of physical discontinuity in the stratum corneum and as such may serve as a penetration pathway for drug delivery through the skin. However, penetration by drugs through the appendages, such as the sweat glands and hair follicles, does not contribute appreciably to topical delivery of medications, because appendages account for only 0.1-1% of the surface of the skin and only 0.01-0.1% of the total skin volume.
Click here to return to Dr. Richard Lee, MD's Q&A page.
|
