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The aim of this work was to evaluate and model the effects of the level of triethyl citrate as a plasticizer and curing conditions on drug release from theophylline tablets coated with a blend of methacrylic acid ester copolymers using response surface methodology. A full-factorial design was used to evaluate the effects of triethyl citrate at 15, 20 and 25 % w/w, curing temperature at 40, 50 and
60 °C and curing time at 1, 2, 4, 8, 12, 24, 48, 96 and 192 h on theophylline release from tablets coated with a blend of Eudragit RL30D and Eudragit RS30D. Drug release was tested in 900 ml of purified water using the rotating paddle method at 50 rpm. Apparent release rate constant (Korsmeyer-Peppas) was used as an index of drug release. Second-order poly-nomial equations were developed to describe drug release as a function of triethyl citrate level, curing time and curing temperature. Triethyl citrate was found to accelerate drug release from film-coated tablets by leaching into the dissolution medium creating pathways for drug diffusion. Increasing curing temperature and time slowed down drug release by in-creasing film coalescence.