Sustained release of theophylline from hydroxypropylcellulose tablets.

Compressed tablets were prepared from theophylline and hydroxypropylcellulose. Effects of the viscosity grades of the polymer, the mixing ratios of two polymers with different viscosity grades, and the polymer contents in the tablets on release patterns of theophylline were examined in vitro. Release rate was decreased with increasing viscosity designation and polymer contents in the tablets. In salivary level profiles of theophylline following oral administration of sustained-release tablets to five human volunteers, a low but sustained level was noted indicating sustained release of the drug from the tablets in vivo.