ON THE EMPLOYMENT OF LAMBDA-CARRAGEENAN IN A MATRIX SYSTEM .2. LAMBDA-CARRAGEENAN AND HYDROXYPROPYLMETHYLCELLULOSE MIXTURES

The suitability of lambda-carrageenan-hydroxypropylmethylcellulose (HP MC) matrices for the controlled release of two basic drugs (salbutamol sulphate and chlorpheniramine maleate) has been assessed. The influen ce that the amounts of the two polymers and their ratios have on drug release profiles was studied. Percentages of lambda-carrageenan as hig h as 40% in the matrix gave rise to good early control of drug release , resulting in release profiles close to linearity. The overall releas e rate was usually higher in buffer at pH 1.2 than at pH 6.8, indicati ng the matrix is somewhat sensitive to the dissolution medium pH. This is possibly due to the effect of medium composition on the rate of ma trix erosion. By increasing the content of the more slowly erodible HP MC, differences in release rate related to the dissolution medium coul d sometimes be reduced.