Adsorption, partition and release balances of terbinafine hydrochloride, part I.

In this study the adsorption, partition and releasing balances of terbinafine hydrochloride have been studied. The adsorption isotherms of antifugal drug terbinafine hydrochloride (terbinafine), on the base of its adsorption from aqueous solutions on the surface of activated charcoal, were obtained in the temperature range of 25 to 45 degrees C used UV VIS spectrophotometric method. The experimental data have been analyzed by Freundlich and Langmuir equations to obtain parameters describing properly this adsorption process. The thermodynamic parameters (average change molar Gibbs energy--deltaadG0, enthalpy--deltaadH0 and entropy--deltaadS0) were calculated and compared. The partition coefficient of terbinafine hydrochloride in the system organic phase/water phase with different organic phases (n-butyalcohol, n-hexylalcohol and n-octylalcohol) using the "shake flask" method have been studied. The experimental partition coefficient of terbinafine increased from butylalcohol to octylacohol in the partitioning system. The influence of the concentration of polymer--hydroxy ethyl cellulose (HEC) (2-3%) used for preparation of the hydrogel (terbinafine-HEC-water), on terbinafine release has been studied. Both the concentrations of polymer and the drug had influence on the release process.