Eudragit polymeric films were investigated as a potential drug delivery system for the controlled release of salicylic acıd. The effects of modification in polymeric ratio of both Eudragit RS 100 and RL 100, drug loading and nature of plasticizer on the vitro release of salicylic acid have been examined. The films containing salicylic acid and plasticizer were cast upon plastic substrate and the in vitro release of drug from each film into a receiving medium of citrate buffer (pH 5.03) was measured. The obtained results indicated that the film containing Eudragit polymer and plasticizer affected the drug release rate and that the release followed Higuchi-diffusion model. The release rate was found to enhance with increasing Eudragit RL 100 ratio. The release rate was also found to be directly proportional to drug concentration. Salicylic acid was slowly released from Eudragit RL 100/dimethyl phthalate films and Eudragit RL 100/glycerol tributyrate films. Eduragit films plasticized with glycerol triacetate or polyethylene glycol 400 or propylene glycol produced a fast drug release. Based upon these results, a water soluble highly polar, non complexing plasticizer would tend to increase the drug release from the film. This study demonstrated the in vitro release of Salicylic acid from Eudragit polymeric film as a function of the solubility of the drug in both the polymer matrix and the receiving citrate buffer medium. The results indicated that Salicylic acid was compatible with Eudragit RL 100 as indicated by the clear and transparent formed films.
Also, the characterizations of Eudragit films were conducted by IR-Spectroscopy and Differential Thermal Analysis to explore the possibility of the drug polymer interaction occurring between salicylic acid and either Eudragit RS 100 or Eudragit RL 100.