Enteric coating process of diclofenac sodium pellets in a fluid bed coater with a wurster insert: Influence of process variables on coating performance and release profile

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® MP, in a fluid bed coater with a Wurster insert. Coating experiments were performed following a 2² factorial design to determine the influence of process variables on coating performance, measured by the two response variables: efficiency (η_%) 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/cm²), 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 °C and 75% relative humidity.