Fluid bed coating: the utility of dual programmable pumps for controlled gradient drug deposition on pellets

The objective of this study was to demonstrate the potential use of dual programmable pumps in a fluid bed coating process to manufacture pellets coated with gradient layers of a drug. To achieve this goal, two matrix forming dispersions with an equivalent amount of solids, one containing verapamil HCl as a model drug, and the other without the drug, were forced in a gradient pattern into a fluid bed coater using two pumps joined at Y junction. The two pumps were operated at opposing flow rates via a computer guided program to maximize drug concentration in the inner layers around the core. The difference between gradient and non-gradient drug coating was demonstrated by dissolution studied. Depending on the drug to polymer ratio, verapamil HCl release from gradient layered pellets was delayed over an extended period of time and was significantly different from the non-gradient coated pellets.