Influence of the centrifugal granulating process on the properties of layered pellets

Drug-layered pellets based on microcrystalline cellulose (MCC) beads as substrates were prepared using a laboratory-scale centrifugal granulator. The effect of three independent process parameters (rotor rotation speed, slit air flow rate, and spray air rate) on responses describing the amount of drug loss during the process, amount of agglomerates, bulk density, flowability, friability, shape, and surface roughness were studied using a 3(3) full factorial experimental design. The variables studied were found to have a significant influence on the responses evaluated. Rotor rotation speed and slit air flow rate had a significant positive influence on the amount of drug loss during the process and the amount of agglomerates, whereas rotor rotation speed and spray air rate had the same effect on the bulk density, flowability, and the roundness of the pellets. The amount of agglomerates and the roundness value of the pellets were negatively affected by the spray air rate while the slit air flow rate showed the same effect on the bulk density and flow rate of the pellets. In addition to the main effects, there were some significant paired interactions between slit air flow rate and spray air rate as well as rotor rotation speed and slit air flow rate. Based on the results, the significance of these three parameters should be considered carefully for quality pellet preparation by the centrifugal granulating technique using MCC beads as substrates.