Excipient choice: technical and biological aspects
The choice of the most suitable emulsion, whether for a pharmaceutical or cosmetic product, involves several queries and the optimization of the finished products depends on the answers to these questions.
In recent decades, the perfection of investigation techniques, the increased availability of information and their exchange on international level have led to a decisive evolution in the choice of basic constituents in an excipient for topical use, thus overcoming restrictions due to the limited number of raw materials registered in the pharmacopeia as well as classical formulations based on the utilization of mineral hydrocarbons or lanolin, the dermatologic suitability of which is subject in the literature to diverging opinions.
Cutaneous topical application is a rather unusual administration technique because, apart from occlusive treatment which artificially eliminates direct contact with the outer world, the product is applied in the boundary area between two special biological compartments, i.e. air with everything which this environment implies and the skin consisting of a complex of cells, thoroughly differing from each other and in continuous functional involution which may even be extreme on the outside.
Therefore, an ideal emulsifier shall meet quality, safety and efficacy requirements. It shall ensure biological tolerance, chemico-physical stability and release of the functional substance based upon the properties required from its formulation. Furthermore, it may not biochemically interfer with the active principles in the cream and shall not cause any hazards for the environment.
Xalifin-15 is a non ionic O/W emulsifier, subject to careful analysis and pharmaco-toxicologic evaluation procedures. Since 1959, Xalifin-15 is a leader on the market of bioemulgoids, emulsifiers for cosmetic and pharmaceutical topical applications, having the property not to damage cutaneous glycolitic fission which is a fundamental energetic phase, since it does not alter the correlated enzymic activity.
Besides its contribution to the updating of classic pharmaceutical ointments, Xalifin-15 has also conquered a vast international cosmetic market (UE, USA, Japan, etc.). It permits to obtain emulsions characterized by an excellent organoleptic appearance, stability, spreadability, texture, easy applicability, good adhesion and high skin feel index.
Elementary excipients are obtained by adding water to Xalifin-15 for dermopharmaceutical preparations that are easy to prepare; the analysis of their active principles (such as anti-histamines, corticosteroids, antimicrobic substances) only requires a very simple formulation.
The results of pharmaco-toxicologic and clinical skin tolerance tests have clearly shown their safety, even when Xalifin-15 is applied to the skin of patients suffering from various types of dermatitis, impetigo, urticaria, lupus, psoriasis and of allergy.
As confirmed by release tests in vitro using an absorption simulator and on the skin using radio-isotopes and fluoresceine, Xalifin-15 can release active and functional substances while making them immediately available. Obviously the amount of released active molecules depends also on the type and percentage of lipids and moisturizers in the formulation.
Indeed, when products with a low release rate are formulated (such as emulsions containing UV filters which shall remain at the surface), Xalifin-15 combined with a proper lipid content capable to bind the screening agent and keep it in solution will permit to obtain creams virtually without release.