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Abstract. The aim of this study was to identify and optimize the critical process parameters of the newly developed Supercell quasi-continuous coater for optimal tablet coat quality. Design of experiments, aided by multivariate analysis techniques, was used to quantify the effects of various coating process conditions and their interactions on the quality of film-coated tablets. The process parameters varied included batch size, inlet temperature, atomizing pressure, plenum pressure, spray rate and coating level. An initial screening stage was carried out using a 2 6−1(IV) fractional factorial design. Following these preliminary experiments, optimization study was carried out using the Box-Behnken design. Main response variables measured included drug-loading efficiency, coat thickness variation, and the extent of tablet damage. Apparent optimum conditions were determined by using response surface plots. The process parameters exerted various effects on the different response variables. Hence, trade-offs between individual optima were necessary to obtain the best compromised set of conditions. The adequacy of the optimized process conditions in meeting the combined goals for all responses was indicated by the composite desirability value. By using response surface methodology and optimization, coating conditions which produced coated tablets of high drug-loading efficiency, low incidences of tablet damage and low coat thickness variation were defined. Optimal conditions were found to vary over a large spectrum when different responses were considered. Changes in processing parameters across the design space did not result in drastic changes to coat quality, thereby demonstrating robustness in the Supercell coating process.

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In recent years, there has been increased interest in continuous manufacturing to improve manufacturing efficiencies. The Supercell coater is an example of a quasi-continuous coater capable of integration as an in-line unit operation for handling sub-batches of tablets .The aim of this study was to evaluate the drug-content uniformity of tablets prepared by quasi-continuous drug coating using the Supercell coater. In addition, near infrared (NIR) and Raman spectroscopy were evaluated in parallel as process analytical technology tools for the monitoring of drug content in the coated tablets. Results showed that the Supercell coater was capable of coating tablets continuously with interbatch relative standard deviations of 2.2-4.9%, as measured by NIR spectroscopy and 1.4-5.0%, as measured by Raman spectroscopy. Both NIR and Raman spectroscopic methods were shown to be useful as non-destructive and rapid at-line monitoring tools to evaluate the drug-content uniformity of coated tablets. The spectra obtained from future exhaustive online measurements of tablets may be used as product fingerprints for real-time quality assurance.

Abstract. Pellet coating is traditionally carried out using the Wurster coater. This study investigated the feasibility of pellet coating in a newly developed coater built with a unique airflow system, the Supercell™ coater (GEA Pharma Systems, UK). A full factorial design study was carried out to evaluate the influences of the spray rate of the coating dispersion, batch size of the pellet load, pellet size fraction and plenum pressure of the fluidizing air on the color coating of pellets in the Supercell™ coater. Results showed that pellets could be successfully coated using the Supercell™ coater. Higher plenum pressures and lower spray rates were found to minimize pellet agglomeration during coating. Although coating efficiencies were comparable amongst the different pellet size fractions, larger batch sizes of pellets were coated with higher efficiencies. Process optimization was carried out for each pellet size fraction and a large batch size (120 g) in combination with a high plenum pressure (1,500 mm WC) were deemed optimal. Optimal spray rates differed according to pellet size fraction and a lower spray rate was required for smaller pellets. Pellet flow patterns observed during coating were dependent on the pressure drop across the fluidized load. A 'swirling' pellet flow pattern was generally observed at coating conditions which led to optimal outcomes.