The MCC–lactose formulations produced tablets of a lower crushing strength than those of the MCC–DCP formulations for all
the mills evaluated. Although all the granulations performed similarly, some differences in tabletability and compactibility
were evident. One noteworthy difference was a higher tablet-crushing strength for the Gerteis-milled material. Tablets had
an approximately 0.5 MPa higher strength compared with the other milled lots. The authors found no definitive explanation
for these results.
Although all the granulations have a flowability rating of good, the Gerteis granulation had the lowest value of 8.0, compared
with the 9.1 and 9.0 for the M5A and Comill, respectively. The lower flowability value suggests a higher level of smaller
particles in the granulation and correlates with the laser-diffraction data showing the Gerteis material having the smallest
D10 and D50 particle-size values. However, the Gerteis material also has the highest D90 value and the greatest breadth of
particle size for the three granulations. The smaller particle size and greater breadth of this granulation may contribute
to the higher tabletability and compactibility observed. Also, the difference in particle size could be attributed to the
ribbon properties.
Table VII: Microcrystalline cellulose–lactose compression properties.
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Review of the ribbon characterization for the individual bags collected (see Table III, bag #5, 6, 7) during roller compaction
suggests that the ribbons used for the three conventional mill types have identical solid fraction and thickness. The ribbon
tensile strength used for the Gerteis milling, however, was the lowest of the three. It is possible that the lower strength
of the ribbon contributed to the difference in granulation-particle size, thus leading to a difference in bonding properties
and tablet-crushing strength.
Overall, formulation composition, not mill type, had the most significant effect on compaction properties. Compression using
a high-speed rotary tablet press confirmed that differences in the formulation composition had an effect on tabletability
and compactibility and that mill type did not significantly influence the tabletability and compactibility of the formulations.
Acknowledgments
The authors acknowledge Barbara Spong's active support of this study.
Thomas A. Vendola* is a scientist in solids development, and Bruno C. Hancock is a research fellow in material sciences at Pfizer, Eastern Point Rd., Groton, CT 06340, tel. 860.441.4430, fax 860.441.3972,
thomas.a.vendola@pfizer.com
*To whom all correspondence should be addressed.
Submitted: Jan. 28, 2008. Accepted: Mar. 20, 2008.
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