EVALUATION OF HYDROXYETHYLCELLULOSE AS A HYDROPHILIC SWELLABLE MATERIAL FOR DELAYED-RELEASE TABLETS

Delayed-release tablets of diltiazem hydrochloride (DIL) were prepared by using AL-15 type hydroxyethycellulose (HEC) as a matrix material. The tablet consisted of a core tablet containing 30 mg of DIL and an o uter shell formed by compressing HEC, The lag time to start the rapid release of DIL was more prolonged in the tablets consisting of a small er particle size (20--53 and 53-106 mu m) of HEC than those of the lar ger particle size (106-250 and 250-355 mu m). However, there was littl e difference in the release rate of DIL among the two kinds of tablets , The rate of water uptake was greater in the tablets prepared with th e larger particle size than those with the smaller particle size. Thes e results suggest that the rate of water uptake seems to be a rate lim iting process in setting the lag time, Observation of the surface of t he tablets by electron micrograph showed that with the larger the part icle size the cavity grows larger and with the smaller the particle si ze the cavity grows smaller, The lag time was also prolonged with an i ncrease in the amount of HEC, Consequently, the lag time can be contro lled optionally by changing the particle size and/or the amount of HEC forming the outer shell, This delayed-release system using HEC will b e useful for time-related symptoms which need time-controlled or site- specific delivery in the gastrointestinal tract.