Purpose. The oral treatment with 5-methoxypsoralen (5-MOP) is mandatory in the case of diffused psoriasis, but can be replaced by topical treatment when the number and extension of psoriatic plaques allow it. The aim of this work was to realize a new 5-MOP topical formulation characterized by high skin permeability. Methods. The system realized was a lotion (5-MOP content 0.06 % and 0.13 % w/w), containing lecithin and cholesterol. The permeation of 5-MOP from the lotion was studied "in vitro" through rabbit ear skin, using Franz diffusion cells. Since the psoralen has very low water solubility (3 mcg/ml at 25 °C), the receptor solution contained beta-cyclodextrin in order to guarantee sink conditions. Results. The results obtained show that the lotion was able to improve the permeation characteristics of 5-MOP compared to other topical formulations (such as the water solution or the gels currently used in therapy). In particular, compared to the gel formulation, the 5-MOP flux was doubled and the lag time was reduced from 1 h to a few minutes. Both can be an advantage in the practical application, since can shorten the application time before UV irradiation. The increase of drug concentration from 0.06 to 0.13 % did not modify drug permeation. Conclusion. In conclusion, the new formulation shows very good permeation characteristics and can constitute a promising alternative to the existing formulations in the topical treatment of psoriasis.
A new 5-methoxypsoralen formulation for the topical treatment of psoriasis
COLOMBO, Gaia;
2001
Abstract
Purpose. The oral treatment with 5-methoxypsoralen (5-MOP) is mandatory in the case of diffused psoriasis, but can be replaced by topical treatment when the number and extension of psoriatic plaques allow it. The aim of this work was to realize a new 5-MOP topical formulation characterized by high skin permeability. Methods. The system realized was a lotion (5-MOP content 0.06 % and 0.13 % w/w), containing lecithin and cholesterol. The permeation of 5-MOP from the lotion was studied "in vitro" through rabbit ear skin, using Franz diffusion cells. Since the psoralen has very low water solubility (3 mcg/ml at 25 °C), the receptor solution contained beta-cyclodextrin in order to guarantee sink conditions. Results. The results obtained show that the lotion was able to improve the permeation characteristics of 5-MOP compared to other topical formulations (such as the water solution or the gels currently used in therapy). In particular, compared to the gel formulation, the 5-MOP flux was doubled and the lag time was reduced from 1 h to a few minutes. Both can be an advantage in the practical application, since can shorten the application time before UV irradiation. The increase of drug concentration from 0.06 to 0.13 % did not modify drug permeation. Conclusion. In conclusion, the new formulation shows very good permeation characteristics and can constitute a promising alternative to the existing formulations in the topical treatment of psoriasis.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
