Mm. Meshali et al., PREPARATION AND EVALUATION OF THEOPHYLLINE SUSTAINED-RELEASE TABLETS, Drug development and industrial pharmacy, 22(4), 1996, pp. 373-376
Formulations were prepared containing 50% theophylline; 0%, 5%, 10%, 2
0%, 30%, or 49.5% of a new sustained-release agent (Carbopol(R) 974P);
0.5% lubricant, with the remainder of the formula consisting of spray
-dried lactose. Similarly, a formulation containing 30% Carbopol 934P
was prepared for comparative study. The tablets produced showed good m
echanical properties. The disintegration time of the tablets was depen
dent on the type and percentage of the sustained-release agent as well
as the pH of the medium. The drug release profiles were consistent wi
th the disintegration time; increasing the percent of Carbopol 974P in
the tablet and holding its weight constant resulted in a decrease in
drug release rate. Approximately 10% Carbopol 974P provided the same s
ustained-release mechanism as 30% Carbopol 934P without tablet stickin
g during compression. Carbopol 974P matrices exhibited release profile
s which were best described by mixed zero-order and Higuchi linear squ
are root of time relationships. This means that mixed barrier and matr
ix diffusion-controlled mechanisms were operative.