FORMULATION OF CONTROLLED-RELEASE LITHIUM-CARBONATE TABLETS BY FLUID-BED TECHNIQUE

The importance of controlled release (CR) formulations of lithium carb onate is well recognized. Some such formulations have been marketed bu t in general only patented. The purpose of this work was to develop an air suspension method, using a laboratory scale fluidized bed drier t o coat the lithium carbonate granules. Different polymers including Eu dragits(R) L 100, S 100, RL 100, L 100 + S 100, (50: 50), RL 100 + RS 100 (50:50), ethyl cellulose and Eudragit(R) RS 100 + ethyl cellulose (50: 50) were utilized. The drug release medium consisted of distilled water in most experiments, but the effect of varying the pH on the re lease behaviour of the drug was also investigated using other dissolut ion media. Of the polymers investigated, Eudragit(R) RS 100, ethyl cel lulose and Eudragit(R) RS 100 + ethyl cellulose (50:50) exhibited suit able release characteristics when used as coating materials in this st udy. The release profiles were analyzed from the standpoint of diffusi on controlled processes and exhibited first order kinetics. Drug relea se was faster from tablets containing Eudragit(R) L 100 and S 100 due to the effect of the polymer on the pH of the dissolution medium.