Targeted and sustained delivery of hydrocortisone to normal and stratum corneum-removed skin without enhanced skin absorption using a liposome gel

Judging from hydrocortisone concentration in dosing area, the extent of absorption was reduced in the liposome-gel formulation. However, higher and sustained skin concentrations of hydrocortisone were achieved for the liposome-gel as compared to the ointment. Drug concentration in both viable and deep skin reached its maximum within 0.5 h after application of both formulations to both skin types. Drug concentrations in both skins from the ointment declined with time, while those from the liposome-gel were greatly sustained. The sustainment by the liposome-gel was more remarkable in the viable skin than in the deep skin. Drug concentration in the viable skin could be maintained at a nearly constant level for over 8 h by applying the liposome-gel. As a result, a 5-fold higher viable skin drug concentration was obtained from the liposome-gel than from the ointment at 8 h after the application to the SC-removed skin. However, the plasma concentration of hydrocortisone at 4 h from the liposome-gel was only one-fourth (p<0.01) the value from the ointment when the drug was applied to the SC-removed skin, consistent with. the lower urinary (one-third, p<0.05) and fecal (one-half, p＜0.05) excretion. Conclusions : Retarded diffusion of the drug from the skin to the systemic blood stream appears to be a potential factor in the sustained skin concentration of hydrocortisone from the liposome-gel, Interaction of hydrocortisone in the skin with phosphatidylcholine, a component of the liposomes and skin, may well be a factor in retarding the diffusion of the drug in the skin.