EXCLUSION OF THE LOCAL-ANESTHETIC PROCAINE HYDROCHLORIDE FROM A SURFACE-ADSORBED FILM AND MICELLE OF DECYLAMMONIUM CHLORIDE

Incorporation of the local anesthetic procaine hydrochloride (PC . HCl ) into surface-adsorbed films and micelles formed by decylammonium chl oride (DeAC) was investigated by measuring the surface tensions of aqu eous solutions of a DeAC-PC . HCl mixture. The thermodynamic quantitie s of the miscibility in these molecular aggregates, the total surface density, and the compositions of PC . HCl in the surface-adsorbed film and micelle were calculated by applying thermodynamic equations to th e surface tension data. The phase diagrams of surface adsorption and m icelle formation showed a peculiar feature; namely, the compositions o f PC . HCl in the adsorbed film and micelle showed negative values ove r the whole composition range measured. The negative values were cause d by the exclusion of the PC . HCl molecules from the adsorbed film an d the micelle of DeAC. PC . HCl was not incorporated into such hydroph obic environments. In contrast, tetracaine hydrochloride (TC . HCl) wa s incorporated into the adsorbed film and micelle of DeAC at all DeAC- TC . HCl compositions. The difference in incorporation between TC . HC l and PC . HCl is attributable to the hydrophobicity of their molecule s.