Influence of ionic strength on drug adsorption onto and release from a poly(acrylic acid) grafted poly(vinylidene fluoride) membrane

Ion exchange resins have several applications in pharmacy for contolled or sustained release of drugs. In the present study, effects of the ionic stre ngths of adsorption medium and dissolution medium on drug adsorption onto a nd release from a acrylic acid grafted poly(vinylidene fluoride) (PAA-PVDF) were studied. Despite their porosity, PAA-PVDF membranes act reasonable we ll as cation exchange membranes. It was observed, that ionic strength of ad sorption medium, degree of grafting and concentration of propranolol-HCl in adsorption medium affect propranolol-HCl adsorption onto the membrane. The fluxes of smaller molecules (MW < 500) across the membrane decreased with ionic strength of buffer solution, whereas the fluxes of the large molecule s (FITC-dextran, MW 4400) increased with ionic strength. Release rate of ad sorbed propranolol-HCl from the membrane into phosphate buffer was greatly affected by ionic strength of adsorption medium. These results can be expla ined by a cation exchange process between membrane and cations present in t he buffer solution and swelling behavior of the grafted PAA chains. (C) 199 9 Elsevier Science B.V. All rights reserved.