title: Transdermal delivery of hydrocortisone from eucalyptus oil microemulsion: effects of cosurfactants.
abstract: This study investigated the effects of cosurfactants on the transdermal delivery of hydrocortisone (model drug) from eucalyptus oil microemulsion. Eucalyptus oil which was successfully employed for steroidal drugs was used as the oil. Tween 80 which was readily miscible with eucalyptus oil was used as surfactant. Ethanol, isopropanol and propylene glycol which are relatively tolerable by the skin were employed as cosurfactants. Pseudo-ternary phase diagrams were constructed in the presence and absence of cosurfactants. Microemulsion formulations containing 20% oil, 20% water and 60% of either Tween 80 or 1:1 surfactant/cosurfactant mixture were compared. Incorporation of cosurfactants expanded the microemulsion zone. The cosurfactant free microemulsion was viscous showing pseudo-plastic flow. The cosurfactant containing preparations were less viscous with Newtonian flow. The drug loading and release rate were increased in the presence of cosurfactants with the release depending on the viscosity. Incorporation of hydrocortisone in microemulsion increased the transdermal flux compared to saturated aqueous solution. The presence of cosurfactants increased the transdermal drug flux compared to the cosurfactant free formulation. Ethanol produced the greatest effect followed by propylene glycol and isopropanol. The presence of cosurfactant and its type can thus affect both the phase behavior and the transdermal delivery potential of microemulsion.
authors.affiliation: Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh 11451, P.O. Box 2457, Saudi Arabia. gmmelmag@yahoo.com
authors.forename: Gamal M
authors.initials: GM
authors.lastname: El Maghraby
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage*; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid; D004655:Emulsions; D005052:Eucalyptus / Q000737:chemistry*; D000078122:Eucalyptus Oil; D005079:Excipients; D006854:Hydrocortisone / Q000008:administration & dosage*; D039821:Monoterpenes / Q000737:chemistry; D009822:Oils, Volatile / Q000737:chemistry*; D010316:Particle Size; D011136:Polysorbates; D011817:Rabbits; D012869:Skin Absorption; D012995:Solubility; D013501:Surface-Active Agents
chemical_list: D000893:Anti-Inflammatory Agents; D004655:Emulsions; C511306:Eucalyptus terpene oil; D005079:Excipients; D039821:Monoterpenes; D009822:Oils, Volatile; D011136:Polysorbates; D013501:Surface-Active Agents; D000078122:Eucalyptus Oil; D006854:Hydrocortisone