Preparation of coated particles using a spray drying process with an aqueous system

Abstract

Coated theophylline particles were prepared by a spray-drying process. The process was carried out using an aqueous solution of hydroxypropylniethylcellulose as the coating polymer. The effects of spray nozzle size, inlet drying temperature, drying air flow rate, feed spray rate and atomizing pressure were studied. The flow properties of the spray-dried particles improved with decrease in the air-to-liquid diameter ratio of the nozzle and increase in the inlet temperature. A high inlet drying temperature produced coated particles with a slower drug dissolution rate. The particles that had been spray dried at a faster drying air flow rate were found to have better flowability, as indicated by lower values of Kawakita's constants, a and 1/b, Hausner ratio and Carr index, and longer dissolution T50% values. High feed spray rates resulted in ineffective atomization, producing badly formed spray-dried products. Atomizing pressure affected only the particle size of the product formed. The smaller particles had a higher dissolution T50% and were more cohesive. © 1991.