RELEASE OF TRITIUM-LABELED ESTRADIOL STEROIDS FROM FULLY SWOLLEN HYDROGELS OF POLYURETHANE NETWORKS

Diffusion of uniformly dispersed tritium-labeled estradiol in water-sw ollen poly(ethylene oxide) -based hydrogels was studied by assaying th e release of solute from cylindrical hydrogels into a finite volume of solution at 37-degrees-C. Fractional release followed a t0.5 relation ship for a range of radii between 0.20 and 0.35 cm and different polym er compositions with equilibrium water uptake of 220-750 parts per hun dred dry polymer. Values of the diffusion coefficient were calculated from the fully swollen hydrogels, which represents the swelling and re lease profile quite accurately. (C) 1994 John Wiley & Sons, Inc.