Design of prolonged-release microcapsules containing diclofenac sodium for oral suspensions and their preparation by the Wurster process

Prolonged-release microcapsules of diclofenac sodium (DS), an acidic drug, applicable as an oral suspension for twice-a-day administration were designed. The microcapsules with a mass median diameter of around 100 mu m and a high drug content were intended to exhibit a preferably prolonged release of highly water-soluble DS when prepared by the Wurster process-a spray coating method using a spouted bed assisted with a draft tube. The microcapsule was composed of a calcium carbonate core of 32-44 mu m, a drug-layer of DS, hydroxypropyl cellulose and polyethyleneglycol 6000, an undercoat of Eudragit L30D and a release-sustaining coat of Eudragit RS30D. Eudragit L30D films were undercoated to decrease the solubility of DS within the environment of the microcapsules and thereby to prolong the drug release. This made it possible to decrease the amount of Eudragit RS30D membrane required to prolong the drug release, leading to decrease in the particle size of products and achievement of high drug content. As a result, prolonged release microcapsules with a mass median diameter of 92 mu m and a drug content of 29% could be obtained. (C) 1997 Elsevier Science B.V.