The objective of this work was to study the coating process of diclofenac sodium pellets, with the commercial aqueous coating suspension for enteric release - Acryl-Eze (R) MP, in a fluid bed coater with a Wurster insert. Coating experiments were performed following a 2(2) factorial design to determine the influence of process variables on coating performance, measured by the two response variables: efficiency (eta(%)) and agglomeration index (m(agg%)). Both response variables were found to be affected by inlet temperature and suspension flow rate with a 95% confidence level. This work also studied the release of diclofenac sodium coated and uncoated pellets in HCl 0.1 N and pH 6.8 phosphate buffer media. Results showed that the release of diclofenac sodium during the buffer stage was affected by the prior exposure to the HCl 0.1 N medium and a polymer weight gain above 9.7% (2.7 mg/cm(2)), was needed to modify the release in such a way that it remained below 10% for the first 120 min in HCl 0.1 N and above 75% in pH 6.8 for the next 45 min. Neither the drug content nor the release profiles were significantly affected by storage at 40 degrees C and 75% relative humidity. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.