Preformulation studies and formulation strategies on khellin, an old/new antivitiligo agent: Interaction with cyclodextrins, solubility in mixed solvent systems and permeation through artificial membranes

Solubility and phase-solubility studies were performed on khellin, a member of the psoralens' family with interesting antivitiligo properties, in order to achieve a correct formulation for topical dosage forms. γ- cyclodextrin, hydroxypropyl-β-cyclodextrin and dimethyl-β-cyclodextrin allowed a significant enhancement of khellin's solubility in aqueous media, especially when used in combination. Water-organic solvents systems (2- propanol and propylene glycol) were used to prepare gels containing significant amounts (0.5, 1% by weight) of the active ingredient. Permeation of khellin from topical formulations was also investigated.