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Table I: A comparison of the flowability index and the coefficient of variation of typical pharmaceutical dosage forms.
Capsule Size
Flowability
Index
3600 Prod/Hr
No. I+ No. O+ Dia. 6T Dia. lot Dia. 13x Dia. 20* Dia. 8.55 Dia. 115 Dia. 11.55 17.5 X 7.15 19.5 X 8.55
4
5
6
7
8
10
12
20
0.52
22
1.20
24
1.76
26
2.24
1.56
30
3.33
32
* Capsules are calculated on the basis of contents without enclosure.
The latter limits are much more restrictive than the former;
this means that blends for tablets must frequently be
granulated.
Conclusions
We have defined powder jlowability and outlined the
parameters affecting its quality. Of particular importance
are powder bulk density, which can be easily measured and
can aid the powder's flow, and the presence of flocculi,
which can obstruct powder flow.
In addition, we have defined the formulas for determin-
ing flowability. These formulas can be expressed as follows:
flowability = l/diameter (in centimeters) determined by
the test to be
The denominator is the viscosity coefficient and includes all
the factors that oppose the powder flow. The numerator in-
cludes two parameters that aid the powder flow: bulk den-
sity and gravity acceleration. The electrostatic charge does
not appear in this equation, although it may interfere
indirectly. In fact, as mentioned earlier, a weak electrostatic
charge can help eliminate flocculi, which reduces the K
value. A strong electrostatic charge, you will recall, turns
the fines away from each other, provoking a reduction in
tion in flowability.
Low bulk density has two consequences: low weight and
low flowability. During wet or dry granulation, therefore,
Coefficient of Variation of Average Weight*
13,000 Prod/Hr
1.10
1.17
1.28
1.32
0.98
Tablet Size
90,000 Prod/Hr
1.09
0.93
0.60
1.30
both bulk density and flowability should be maximized.
Moreover, prior to either capsule or tablet manufacturing,
one should test both nontapped bulk density and flow-
ability since these two parameters allow one to calculate the
value of K.
Italy), we have adopted flowability-index numbers that
were obtained with the simple apparatus described herein
as receiving and quality control specifications for all pow-
ders. The flowability index is now specified on all materials
purchased from our suppliers.
Since these procedures were inaugurated, incidences of
downtime and of failure of products to pass necessary tests
(e.g., dissolution and product uniformity) have been re-
duced to zero. The value of establishing a limits of flowa-
bility index of feed powders to ensure product uniformity
is suggested by the data in Table 1. The savings in produc-
tion time and labor and the decrease in recalls have more
than offset the investment made in adapting this uncompli-
cated test to purchasing, quality assurance, and manufac-
turing protocols.
Augsberger, L.L, and Shangraw, R.F.,
No. 4, 1966, p. 418.
J. Am. Pharm. Assoc., Sci. Ed.,
Nelson, E.,
435.
J. Pharm. Pharmacol.
Train, D.,
Hammerness, F.C., and Thompson, H.O.,
Assoc., Sci. Ed.,
47, 1958,
Vol.
Pharm. Sci.,
5.
Gold, G., et al., J.
Teledyne Hanson Research Document 99-380-001 Rev. 06-19
1.17
1.32
0.87
3.69
J. Pharm Sci.,
Vol. 55,
44, No. 7, 1955,
Vol.
Vol. 10, 1958, p. 127T.
J. Am. Pharm.
58.
p.
55, No.
Vol.
11, 1966, p. 1291.
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