Pharmaceutical development of enteric-release hard gelatin capsules in the compounding setting

Enteric coated capsules are characterized by their resistance to dissolution in low pH environments, such as the stomach, and by their rapid disintegration in a higher pH environment, such as the intestine. The surface of hard gelatin capsules is usually smooth and nonporous, which limits their coating efficiency. We developed a simple, quick, and easily reproducible compounding preparation method for enteric-release hard gelatin capsules. Twenty-two batches of 60 diclofenac sodium capsules each were prepared and then divided into three groups. Each group was submitted to a different coating process using a small-scale enteric coating machine and a coating process based on the atomization (spraying) of organic solutions of polymers. The results of dissolution testing were compared statistically within the groups and also with a reference drug control (Voltaren DR). Some of the batches in group I and all the batches in groups II and III met the pharmacopeial requirements for enteric release, in both acid and pH 6.8 phosphate buffer stages. Dissolution of capsules coated with Eudragit L100 was more efficient than that of other tested systems (P less than 0.05). The dissolution assay results for group III in the acid stage were superior to the results for the reference drug, but no statistical difference was noticed between these two in the phosphate buffer stage. Diclofenac sodium hard gelatin capsules coated with cellulose acetate Phthalate or Eudragit L100 presented dissolution performance that met pharmacopeial requirements. Furthermore, results obtained with Eudragit-coated capsules were comparable to those obtained with the reference drug.