The effect of equal porosity on tablet properties
The author performed an experiment using an ibuprofen 85 DC formulation with 0.5% magnesium stearate. The tabletting was done
on the "MODUL P" tablet press (GEA Courtoy, Halle, Belgium). This press is equipped with the air compensator at precompression
and main compression.
The advantage of equal porosity tableting is the reduction of variability in density, tensile strength, and disintegration.
Compression to EF.
For the above formulation, a series of tablets was compressed at a constant force of 650 daN with a nominal tablet weight
of 233 mg.
Tablets were compressed within ± 4% of their nominal weight. All tablets were compressed to the same peak compression force.
Compression to ET.
The same series of tablets was compressed to ET. The distance between the two rollers remained constant throughout compression.
Results
Figure 5
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Figures 5–8 show the analysis. The weight variation demonstrates an increase of force when the machine uses the ET mode and
tablet weights increase.
Figure 6
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The influence of tablet weight on density for ET and EF.
Density increases as tablet weight increases. Density decreases when tablet weight decreases. The variability of the density
during compression to EF is 1.1%. The variability of the density during compression to ET is 8%. Both tests used the same
series of tablets within the same weight range.
Figure 7
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Testing the tablets for tensile strength.
The variability in tensile strength was more significant than that of density. Tablets compressed to EF showed as little
as 1.2% variation. Tablets compressed to ET showed as much as 29.6% variation.
Figure 8
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Testing the tablets for disintegration time.
Disintegration time varied widely according to the compression technique. Tablets compressed to EF showed only 14.5% variability
in disintegration time. Tablets compressed to ET, however, showed more than 105% variability in disintegration time.
Conclusion
The data were gathered under controlled conditions for ibuprofen 85 DC, and tablets were compressed within the US Pharmacopoeia's
weight-variation limits.
Tablets compressed under equal force (EF) showed a much more consistent density, tensile strength, and disintegration rate
than tablets compressed to equal thickness.
Different results might be expected from other drug formulations, but these data clearly indicate the advantage of a rotary
press with EF capability.
Machines with both capabilities, therefore, give formulation and production departments great scope for improving tablet quality.
Johan Van Evelghem is a product and compression-technology manager at Courtoy, 9165 Rumsey Rd., Columbia, MD 21045, tel., 410.997.6692, johan.vanevelghem@geacourtoy.com
Reference
1. K.A. Khan and C.T. Rhodes, "Effect of Variation in Compaction Force on Properties of Six Direct Compression Tablet Formulations,"
J. Pharm. Sci.
65 (12), 1835–1837 (1976).
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