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Microagglomeration of pulverized pharmaceutical powders using the Wurster process I.:Preparation of highly drug-incorporated, subsieve-sized core particles for subsequent microencapsulation by film-coating

International Journal of Pharmaceutics
Publication Date
DOI: 10.1016/s0378-5173(99)00006-x
  • Acrylic Polymer
  • Agglomeration
  • Core Particle
  • Eudragit® Rs30D
  • Film-Coating
  • Wurster Process
  • Microencapsulation
  • Design
  • Pharmacology


Abstract A novel agglomeration process of pulverized pharmaceutical powders into subsieve-sized agglomerates (microagglomeration) was designed for manufacturing highly drug-incorporated core particles for subsequent microencapsulation by film-coating. The microagglomeration of pulverized phenacetin powder, whose mass median diameter was 9 μm, was performed by spraying an aqueous colloidal dispersion of acrylic polymer, Eudragit® RS30D, as a binding/coating agent using a spouted bed assisted with a draft tube (the Wurster process), and the effect of process variables was examined. An appropriate spray liquid flow rate made it possible to produce microagglomerates of 20–50 μm with 60% yield. However, 10% of the product still survived as particles smaller than 10 μm even at the elevated liquid flow rate. In contrast, the survived particles smaller than 10 μm tended to be predominantly reduced to 2%, while coarse agglomerates larger than 53 μm were not excessively produced, by additionally setting a fixed bed of glass beads in the spouted bed apparatus. The length of the draft tube influenced compaction of the agglomerates as well as their surface-smoothening. Equipping the fixed bed of the glass beads and the long draft tube in the spouted bed allowed us to prepare microagglomerates of 20–50 μm at yield of 55% applicable as highly drug-incorporated, free-flowing, surface-smoothed, narrowly size-distributed core particles for subsequent microencapsulation by film-coating.

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