Amphiphilogels as drug carriers: effects of drug incorporation on the gel and on the active drug.

Amphiphilogels (a subset of organogels) are being studied as drug carriers in our laboratories. In this paper, the effects of drug incorporation on the drugs and the gels are discussed. Amphiphilogels were prepared by heating a mixture of the gelator (sorbitan monostearate or sorbitan monopalmitate) and the liquid (e.g. Tweens or liquid Spans) to form a solution/dispersion, which was cooled to the gel state. Drugs were dissolved by heating a mixture of the drug and the gel and cooling the resulting solution. Hydrophilic gels (composed of hydrophilic Tweens as the liquid) were more effective solvents than hydrophobic ones (composed of hydrophobic Span 20 or 80 liquids). The latter's solvent capacity could, however, be increased by the inclusion of co-solvents, such as propylene glycol and ethanol. Drug incorporation at 10% w/w did not cause any detrimental changes in gel stability, while the drug's release rate was dependent on its concentration and on the nature of the gel's liquid component (which influences drug solubility), but not on gelator concentration or on the method of drug incorporation. This study shows the importance of the nature of the gels' liquid component and the possibility of using hydrophilic amphiphilogels as solvents for poorly water-soluble drugs.