Soy Lecithin/Isopropyl Palmitate

Isopropyl palmitate is used in topical pharmaceuticl and cosmetic preparations as a non-oleaginous emollient with very good spreading characteristics. It is a clear, coloress to pale yellow-colored, practically odorless viscous liquid that solidifies at less than 16 degrees celcius. It should be stored in well-closed and light-resistant containers.

Lecithin is a complex mixture of phospholipids and other materials. They vary greatly in their physical form, from viscous semiliquids to powders, depending upon their free fatty acid content. They are almost odorless and will vary in color from brown to light yellow. Lecithins are used as dispersing, emulsifying and stabilizing agents. They will decompose at extreme pH, are hygroscopic and will oxidize, darken and decompose at high temperatures. Lecithin should be stored at room temperature protected from light. Refrigeration may cause the material to separate.

The combination of soy lecithin and isopropyl palmitate (especially with Pleuronic F-127) is usefull in pharmaceutical compounding due to the solubilizing and penetration inhancement.

The term penetration enhancer is applied to materials that have a direct effect on the permeability of the skin barrier. Some materials may act by a direct chemical insult on the skin while others may not have a specific barrier effect. The latter may affect the solubility and/or dispersibility of the medicament and/or its delivery system (the vehicle). A variety of organic solvents are known to enhance the percutaneous absorption of medicaments.

Many theories concerning the mechanism of action of penetrants have appeared in the literature.

Surfactants are also used as penetration enhancers. Evidence regarding the influence of detergents and surfactants on epidernael permeability suggests that the effect of surfactants in lowering the surface tension of water is not an important factor in enhancing penetration of the skin even though skin lipids may be removed when the surface tension of water is decreased.

The effect of surfactants as penetration enhancers has been attributed to their ability to bind protein, thereby altering the structure of the stratum corneum. The importance of protein denaturation by some surfactants in increasing skin permeability has also been reported in more recent studies.

Miscellaneous Factors:

Several other factors may influence the percutaneous absorption of medicaments: the site of application, the length of time such application remains in contact with the skin, the amount of inunction used in applying the medicated application, and skin temperature. Drugs which penetrate the stratum corneum do so most readily where the outer keratic layer is thin.

Acology Prescription Compounding Center - (http://www.Rx4u.com)