ETHYLCELLULOSE MATRIX CONTROLLED-RELEASE TABLETS OF A WATER-SOLUBLE DRUG

Pseudoephedrine hydrochloride was used as a model drug to prepare direct compression sustained release tablets with ethylcellulose (EC). Initially, different viscosity grades of EC were studied. An increase in viscosity grade resulted in a marginal to moderate increase in the release rate. However, lower viscosity grades produced harder tablets. The highly compressible 10 cp grade was used to study the effect of drug loading, particle size, compression force, and magnesium stearate concentration on release properties. The rate of drug release decreased with a decrease in the drug concentration in the matrix. Except for tablets prepared with EC having a particle size fraction 250-420 and 177-250 mu m, drug release up to 80% exhibited a square root of time dependency and tablets remained intact during dissolution. Tablets prepared with either the EC 250-420 or 177-250 mu m particle size fraction eroded. The square of the release rate is proportional to drug concentration in the matrix, indicating that the release of pseudoephedrine hydrochloride from EC matrices is primarily matrix-controlled.