Controlled-release tablet matrices from carrageenans: compression and dissolution studies.

This study investigates the potential of two commercial carrageenans, Gelcarin GP-379 (iota-carrageenan) and Viscarin GP-209 (lambda-carrageenan) to be used for the preparation of controlled-release tablet matrices. Tablets were compressed on an instrumented Stokes single punch machine and compression characteristics of the carrageenans were analyzed. Heckel plots using out-of-die tablet densities were linear with calculated yield pressures of 81.3 MPa and 105.2 MPa for iota- and lambda-carrageenan, respectively. Drug release from tablet formulations that contained equal amounts of the two carrageenans had near zero-order release profiles. There was little or no effect of tablet compression pressure on the drug release profiles from 70 to 175 MPa. As drug loading was increased from 5 to 20%, the diffusional exponent decreased from 1.056 to 0.678. Thirty percent drug loading resulted in breakup of tablets during dissolution and departure from zero-order release. Multiple regression analysis was used to predict the time for 50% release as a function of the concentration of the two carrageenans and a third filler material, microcrystalline cellulose. Predicted values were in good agreement with observed values and R2 for the final cubic model was 0.9984.