Delivering drugs through the skin.

Skin serves mostly as a protective barrier, working to keep things out of the body. Yet, as J. Howard Rytting, a chemist at the University of Kansas in Lawrence, points out, it can also act as a route for getting drugs in.

Rytting and his colleagues have developed a new class of agents that enhances skin penetration and can help ferry certain drugs into the body. The researchers believe the new agents will prove useful in treating arthritis and psoriasis, reducing inflammation, and relieving pain.

The penetration enhancers, known as dialkylamino acetates, can boost absorption rates more than 400 times. Tests on skin shed by snakes, which has an absorption rate similar to that of human skin, showed that the new agents increase penetration of hydrocortisone, used to treat scaly skin, and indomethacin, an arthritis remedy.

Administering some drugs directly through the skin, says Rytting, can avoid certain side effects and bypass the breakdown of active agents in the gastrointestinal tract and liver. If, for example, nonsteroidal anti-inflammatory agents could be applied directly to sore joints, a higher percentage of the drug would reach its destination instead of being dispersed throughout the body. Moreover, patients who are unconscious or nauseated might absorb drugs more effectively through skin patches.