Pharmaceutical Technology: Controlled Drug Release, Volume 2

MULTIPARTICULATES [CH. 13 147
Fig. 3—Scanning electron micrograph of the tablet fracture surface from a ‘matrix’ tablet. Compressive force, 2 kN;
core:coat ratio, 1:1.
Fig. 4—Scanning electron micrograph of the tablet surface from a ‘microcap’ tablet, after dissolution. Compressive
force, 10 kN; core:coat ratio, 2:1.
over a period of 2h. At 5 and 10 kN the rate of release from both tablet ratios was approximately
the same, with the 2:1 ratio tablets reaching the steady rate of release earlier.
At pH 7 (Fig. 6) the 2:1 matrix tablets still show a significantly faster release than does the 1:1
system. The latter system, when prepared under both 5 and 10 kN compressive forces, releases
more slowly than either of the two microencapsulated systems, with the latter showing similar
percentage release rates to each other. Over the initial 2 h period as far greater percentage was
released from the ‘microcap’ tablets than in pH 2, but the increase in release from the matrix
tablets was by comparison small.
At pH 9 there were significant differences in the percentage released between systems, other
than the 2:1 matrices, but the change in preparative compressive forces produced only a small
reduction in release.