Enhancing effect of absorption promoters on percutaneous absorption of a model dye (6-carboxyfluorescein) as poorly absorbable drugs. II. Study on the absorption promoting effect of azone.

The percutaneous absorption of drugs was investigated in rats by measuring plasma levels, using mainly 6-carboxyfluorescein (CF) as a model of poorly absorbable drugs. Azone (AZ), a new useful promoter for the percutaneous absorption of drugs, was used instead of dimethylsulfoxide. We have examined the effects of the solubilized state and concentration of AZ on the percutaneous absorption of CF. AZ was dissolved with the aid of surface-active agents, beta-cyclodextrin (CD) or dimethyl-beta-cyclodextrin (DMCD). When AZ (2 v/v%) was dissolved completely by a surface-active agent (HCO-60: polyoxyethylene hardened castor oil derivative), plasma CF levels showed the highest value. Plasma CF levels following the administration of CF with AZ which formed a complex with CD or DMCD were scarcely increased as compared to that of CF alone. In the case of fluorescin (FL), which has a higher partition coefficient than CF, the percutaneous absorption of FL was more enhanced by the addition of AZ than in the case of CF.