MicroCoat™: Improved Drug Release Control For Sustained Release Multiparticulates

Kavil Patel, Valentyn Mohylyuk, Nathan Scott, Darragh Murnane, Craig Richardson, Daniel Marshall, Fang Liu*

*Corresponding author for this work

Research output: Contribution to conferencePosterpeer-review


Introduction: Most oral dosage forms such as tablets and capsules are not suitable for paediatric and older patients with swallowing difficulties. Drug-containing sustained release microparticles are suitable to produce flexible dosage forms, such as oral liquid suspensions, which are appropriate for these patients. Recent investigations suggest, that particles with size approximately 250 µm and less are preferable for improved patient acceptance [1]. The aim of this investigation was to apply a novel MicroCoatTM technology to improve coating process of small particles of less than 150 µm in size using aqueous sustained release polymer dispersions during Wurster fluid-bed coating. Methods: Cellets 100 (D50=144 µm) was coated in a fluid-bed coater (Mini-Glatt) using aqueous Eudragit RS/RL (9:1) dispersion or with Eudragit NM with and without the application of the MicroCoatTM technology where glidants (magnesium stearate or colloidal silicon dioxide) were added as dry powder during the coating through an external port as processing aids. Processing aids were added every 15 min for the total amount of 4 and 9% based on the dry polymer for Eudragit RS/RL and NM correspondently. Cohesiveness and powder rheology of coated microparticles were characterised with and without mixing with dry powder glidants (magnesium stearate, talc, silicon dioxide, glycerol monostearate) by the determination of densification kinetics (tapped density test), dynamic cohesive index (GranuDrum rotating drum rheometer), basic flow energy, specific energy, conditioned bulk density, permeability and compressibility (FT4 powder rheometer). Results: Without the application of the MicroCoatTM technology, Cellets 100 particles coated with Eudragit RS/RL formed a layer of stuck particles outside the Wurster cylinder resulted in low yield of 39%. The MicroCoatTM technology significantly improved coating process by reducing particle aggregation and increased yield to 96% and 99% for magnesium stearate and colloidal silicon dioxide as processing aids respectively. Powdered glidants decreased cohesiveness of coated microparticles with effectiveness in the following order: silicon dioxide > magnesium stearate > talc > glycerol monostearate (fig. 1). Basic flow energy, specific energy, conditioned bulk density, permeability and compressibility (fig 2) of Eudragit RS/RL coated microparticles with and without mixing with magnesium stearate at 20 and 30⁰C indicate a reduction in powder cohesiveness and increase in powder flow by the addition of dry powder glidants. Conclusion: The addition of dry powder glidants during coating process significantly improved coating process and product yield of particles less than 150 µm size due to the reduction of particle cohesion and facilitating powder flow. Learning Objectives: Explain the possibility to coat particles less than 150 µm with aqueous sustained release polymer dispersion using the fluid-bed coater with Wurster cylinder. Evaluate the rheological properties of coated microparticles to explain the cohesive behaviour of microparticles during coating process. Explain the effect of the dry powder glidant addition during coating on the outcomes of the coating process.
Original languageEnglish
Number of pages1
Publication statusPublished - 21 Jul 2019
Externally publishedYes
Eventhe 2019 Controlled Release Society Annual Meeting & Exposition - Valencia, Spain
Duration: 21 Jul 201924 Jul 2019


Conferencehe 2019 Controlled Release Society Annual Meeting & Exposition
Abbreviated titleCRS
Internet address


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