PURPOSE: In a fluid-bed coating machine, the coating solutions are normally sprayed using a manually controlled peristaltic pump. This study provides a process where two or more coating solutions can be sprayed consecutively using two or more syringe pumps controlled by a computer, to form multiple layers. In this process, the spraying parameters can be controlled easily from a computer. METHODS: Propranolol HCl was used as a model drug. Nine different drug-loaded controlled release coated beads were prepared by using a combination of ethylcellulose and/or chitosan solutions. The pulse-coated beads were prepared by changing the spray rate and/or volume of the polymer solutions. RESULTS: There was a fourfold increase (18 versus 75 minutes) in lag time when the same amount of ethylcellulose (4 g) was dissolved in 100 mL of ethanol instead of 160 mL. When the same amount of drug and ethylcellulose solution was applied on the acrylic coated beads as multiple layers coating, the lag time decreased to only 6 minutes. Similarly, the 50% drug release time also decreased significantly. CONCLUSION: An overall comparison of the dissolution profiles showed that drug release from these coated beads was changed significantly when the sequence of the drug and polymer layers was changed.
PURPOSE: In a fluid-bed coating machine, the coating solutions are normally sprayed using a manually controlled peristaltic pump. This study provides a process where two or more coating solutions can be sprayed consecutively using two or more syringe pumps controlled by a computer, to form multiple layers. In this process, the spraying parameters can be controlled easily from a computer. METHODS:Propranolol HCl was used as a model drug. Nine different drug-loaded controlled release coated beads were prepared by using a combination of ethylcellulose and/or chitosan solutions. The pulse-coated beads were prepared by changing the spray rate and/or volume of the polymer solutions. RESULTS: There was a fourfold increase (18 versus 75 minutes) in lag time when the same amount of ethylcellulose (4 g) was dissolved in 100 mL of ethanol instead of 160 mL. When the same amount of drug and ethylcellulose solution was applied on the acrylic coated beads as multiple layers coating, the lag time decreased to only 6 minutes. Similarly, the 50% drug release time also decreased significantly. CONCLUSION: An overall comparison of the dissolution profiles showed that drug release from these coated beads was changed significantly when the sequence of the drug and polymer layers was changed.