Release rate of drugs from ethyl cellulose coated granules containing caffeine and salicylic acid

Fluidized bed coating with ethyl cellulose., polyethylene glycol mixtures has been utilized for prolongation of drug release from granules containing salicylic acid and caffeine as model drugs. Drug release from the coated granules followed first order kinetics. Particle size of the active material, granule composition and extraction medium pH did not affect the rate and kinetics of drug release. Increase in coat thickness decreased the release rate whereas elevation of the ratio of polyethylene glycol to ethyl cellulose enhanced the release rate to a degree related to the polyethylene glycol concentration. The permeability constants of salicylic acid and caffeine for the ethyl cellulose-polyethylene glycol coatings were of a similar order to those measured previously using solutions of the drugs with planar barrier films.