Effect of Electric Field Strength on Diffusion of Ionic Drugs from Polyacrylamide Hydrogels

The apparent diffusion coefficients, Dapp, and the release mechanisms of ionic-drugs from drug-loaded polyacrylamide hydrogels, drug-loaded PAAM, were investigated for the effects of various drug sizes (Lactic acid, 3.11 {\AA}; Sulfanilamide,3.47 {\AA}; Ampicillin, 5.14 {\AA}), matrix pore sizes, and electric filed strengths. The Dapp of the drugs from the drug-loaded PAAM increases with decreasing drug size, increasing matrix pore size or applied electric field strength. The increase in Dapp can be attributed to the combination of the iontophoresis and the electroporation of the matrix pore. The Dapp of drug from the drug-loaded PAAM apparently obey the scaling behavior: Dapp/Do=(drug size/pore size)m with the scaling exponent m equal to 0.73 and 0.50 at the electric fields of 0 and 0.1 V, respectively.