This work reports the study of the addition of isopropanol on controlled release of ibuprofen from ethylene vinyl acetate (EVAc) copolymer membranes. An EVAc solution in cyclohexane (4% w/v) containing triethyl citrate (7% w/v) as plasticizer was mixed with ibuprofen at three different concentrations of 4, 6, and 8%. Isopropanol was mixed with each of the previous mixtures to form solutions of 1, 3, and 5% isopropanol concentrations. Samples were solvent cast on glass petridishes to form membranes. Home-made diffusion cells were used for in vitro study. These cells were composed of two compartments, donor (exposed to ambient conditions), and receptor (including buffer solution maintained at 37 degrees C). Each cell was equipped with a sampling port and water in and out system. An ultraviolet spectrometer at 222 nm was used to measure release rates of obtained membranes. The diffusion mechanism for drug release was examined by zero-order, first-order, Higuchi and Korsmeyer-Peppas theories to confirm the obtained membranes follow the matrix-type system. By increasing the drug concentration from 4 to 8%, drug release (cumulative amount) was improved from 20 (47.5%) to 30 (36%) lg/cm(2) after 24 h. Addition of 5% isopropanol to the above samples (4 and 8% loading) further increased drug release to 24 and 43 lg/cm(2). Results were in good agreement with the Korsmeyer-Peppas theory for samples with 4 (% w/w) of ibuprofen. The highest percentage of drug release after 24 h was 59% for the sample with 4% drug loading compared to 50% for the sample with 8% drug loading, both with 5% isopropanol. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122:3048-3054, 2011