An Investigation into the Optimization of Release Profile of Lithium Carbonate from Matrix-type Tablets Containing Carbopols, Pemulen and Eudragits

The influence of various polymers on the release rate of lithium carbonate from matrix-type tablets was investigated in an attempt to formulate a sustained release solid dosage form. For this purpose, tablets containing 450 mg of lithium carbonate along with various amounts of Carbopol 934P, 971P, 974P, Pemulen and Eudragit RLPO as retarding agents and inactive ingredients (e.g. PVP, Avicel or starch) were prepared using wet granulation technique. Tablets prepared were initially placed in a phosphate buffer solution for 7 h and those formulations from which a minimum of 80% lithium carbonate released, were selected for coating process. The amount of drug released was determined by using atomic absorption spectroscopy. The dissolution rate of enteric coated matrix-type tablets were then evaluated in both acidic and basic mediums (1 h and 11 h, respectively). The results showed that Pemulen and Carbopol 971P are not suitable polymers for preparing tablets with desirable release profile, at all concentrations examined. However, it was observed that Carbopol 934P, 974P and Eudragit RLPO are capable of producing tablets with desirable release pattern, at concentrations of 2, 1.5 and 3%, respectively. Tablets containing Eudragit RLPO were found to have the greatest drug release profile, while Carbopol 974P showed the slowest release rate