Studies on percutaneous absorption of drugs. 3. Percutaneous absorption of drugs through damaged skin.

Abstract

1) The percutaneous absorption through the damaged skin lacking stratum corneum greatly increased as compared with those of the intact skin, and the initial absorption pattern which was distinctly recognized in the intact skin almost disappeared in the damaged skin, and the absorption of the durgs occurs by the simple diffusion of a first order rate from the start of the experiment. 2) The absorption of the drugs in the intact skin are almost negligible at pH 6.0 where the most of the drugs ionized, however, in the damaged skin, the absorption of drugs are distinctly found. 3) The amounts of the drugs reserved in the intact skin attained to a definite amount reserved after the lapes of a given time, and are depicted by the plateau pattern. On the other hand, the amount reserved in the damaged skin varied the pattern which has a peak in early time, and the peak of the amount reserved in the skin increased as increasing of the drug concentration of test solution. 4) The amount reserved in the skin and the amount of the drugs decreased from test solution in the damaged skin decreased as decreasing of the fraction of the unionized form of the drugs, and it was recognized that the peak of amount reserved in the skin has a tendency to reach late. 5) After test solution was removed from the applied area, the amounts of both drugs reserved in the damaged skin are almost disappeared within 4 hours, and the ability as a cutaneous reservoir of drugs was missing in the damaged skin.