Release of Glucocorticoids from Ethylcellulose Latex Formulations Prepared as Drug-carrier Complexes and with Microencapsulation Maria Adolfina Ruiz, Maria Encarnacion Morales, Maria Ester Garcia, and Visitacion Gallardo Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Granada, Granada (Spain) Correspondence: Dr. M. A. Ruiz, Dept. Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Granada, 18071 Granada (Spain), Fax +3458248958, e-mail: adolfina@ugr.es The aim of this study was to compare formulations for the modified release of active principles from latex carriers, in which the drug was incorporated by adsorption or microencapsulation. To determine their influence on adsorption and microencapsulation, two glucocorticoids differing in physicochemical properties were tested: water-soluble methylprednisolone sodium hemisuccinate and lipo-soluble budesonide. Ethylcellulose latex was synthesized with the method proposed by Vanderhof and colleagues (latex L), and its particle shape and size were compared with a commercially available latex of similar composition (Aquacoat®). Release studies were done with the method of Mena and colleagues. Assays to quantify adsorption showed that Aquacoat, because of its smaller particle size, adsorbed more of the drug than latex L. To obtain information on how to optimize the production of drug-carrier complexes, adsorption of both drugs on both types of latex was studied under different pH, time and concentration conditions. Adsorption was maximal after about 4 h at pH 5- 6. The two active principles were combined with the latex carrier by encapsulation during synthesis, and drug release was compared in formulations to which PEG or silicone excipients was added. Microencapsulation efficiency ranged from 84 % to 90 % for both active principles. Drug release was greater with the hydrophilic excipient than with the silicone-based excipient. The data showed that encapsulation prolonged the effect of the drug by slowing release. The formulation with PEG excipient yielded the best release values. Key words Corticoids • Controlled release • Ethylcellulose latex |