Pharmaceutical Technology: Controlled Drug Release, Volume 2

18 MATRIX FORMULATIONS [CH. 1
Fig. 3—Effect of grain size for drug A.
with the Moritz TS10 are 166 µm (formula 6) and 152 µm (formula 7). For the granulate prepared
with a planetary mixer, the mean diameter is 326 µm and the distribution is wider (80% between
180 and 500 µm).
If calcium hydrogen phosphate is the only diluent, the dissolution rate is more dependent on pH
variations (Fig. 4) than with lactose: t 50 increases from 8.0 h (pH 2.0) to 22.1 h (pH 7.4) with
calcium hydrogen phosphate, and from 9.7 h (pH 2.0) to 13.7 h (pH 7.4) with lactose.
Fig. 4—Effect of pH for drug A.
Drug B
The dissolution rate does not exhibit significant differences between Methocel E4M CR,
Methocel K4M and Metolose 60SH4000 (formula 8): the respective t 50 values are 1.78 h, 1.86 h
and 1.75 h. Dissolution speed is higher with Metolose 90SH4000 (t 50 =1.06 h) (Fig. 5) and