There is a great variety of known liquid or semisolid preparations for topical application to the body, and they are generally based on aqueous or other polar liquids, on liquid or semisolid lipids, or on mixtures thereof. When the preparation is based on a mixture of an aqueous liquid and a lipid substance, the preparation is an emulsion, which may be a water-in-oil (w/o) emulsion in which the lipid substance is the continuous phase, or an oil-in water (o/w) emulsion in which the aqueous liquid is the continuous phase. Each of these types of emulsions is prepared with its own type of emulsifier. EP-B-69423 shows that the type of emulsion is determined by the type of emulsifier used, rather than by the relative concentrations of aqueous or lipid components present. Examples of known emulsions of the w/o type are the ointments, which generally are semisolid. As examples of known emulsions of the o/w type lotions, which are liquid, and creams and gels, which are semisolid, can be mentioned.
The liquid or semisolid lipids, contained in the above-described liquid or semisolid w/o or o/w emulsions, generally are responsible for a cosmetically and medically important effect, viz. occlusion. By occlusion is meant the formation of a "barrier", which causes reduction of water loss through the epidermis, after treatment thereof with such lipid containing emulsions. The occlusive effect is positively correlated to the lipid content of the emulsion. The resulting desirable cosmetic effect of occlusion is emolliency. The resulting desirable medical effect of occlusion is a better penetration into the skin and a better effectiveness of many medicaments, incorporated into an occluding emulsion, after topical application of the same. On the other hand, such lipid containing emulsions have the disadvantage that they are greasy and messy, resulting in a shining appearance of the treated area and in staining of the clothes, and these undesirable properties are also positively correlated to the lipid content of the emulsion.
H. Tsutsumi et al., J. Soc. Cosmet. Chem., 30, 1979, 345-356 described oil-in-water emulsions of different particle size distribution prepared out of water, solid paraffin (melting point 48.degree. C.) and a mixture of polyoxyethylene (20) sorbitan monooleate and sorbitan monooleate. The solid particles of the resulting emulsions had a mean diameter of about 3-65 .mu.m. The occlusivity of the emulsions was found to be inversely proportional to the particle size. However, in the present inventors' experience these types of emulsions, containing solid paraffin particles of micrometer dimensions (microparticles), were found to be inherently unstable. Also, these types of emulsions were found to exert a lower occlusivity as compared with conventional emulsions.
EP-B-167825 discloses a medicament-containing carrier system for peroral use, comprising a 1-20 wt % aqueous suspension of solid lipoid nanopellets with a particle size of 50-1000 nm, the lipoid particles containing 5-70 wt % of lipids, 0.01-70 wt % of an emulsifier and 0.05-25 wt % of the medicament. Due to their small size, the lipoid particles in toto are easily absorbed from the gastro-intestinal tract. Among the advantages of this type of drug-containing carrier system for oral administration an improved bioavailability of those medicaments, which are poorly soluble, poorly absorbed from the digestive tract, chemically or enzymatically inactivated in the digestive tract or prone to the so-called first-pass effect, is to be mentioned in particular.