Solubilizing potential of submicron emulsions and aqueous dispersions of lecithin.

Aqueous lecithin dispersions (WLD, water-lecithin-dispersion) were obtained by dispersing egg lecithin (1.2 or 2.4% w/w) in an isotonic mixture of glycerol and water. The solubilization potential of the pure phospholipid structures was investigated and compared with that of submicron emulsions containing the same amounts of lecithin and 10 or 20% (w/w) of soya-bean oil. The increase in solubility of the investigated lipophilic drugs in WLD was proportional to the lecithin concentration. Concentration of lecithin in the emulsion was the main factor determining solubility of drugs moderately lipophilic (logP below 2.5), while for more lipophilic compounds the presence of oil was a determinant and for such drugs solubility in submicron emulsion was better than in WLD. WLD obtained in a simple technological process may be considered as a carrier particularly for highly lipophilic drugs: solubility of estradiol in this system was 100-fold higher than in water.