Pharmaceutical Manufacturing Handbook: Production and

Water absorption, %
8
7
6
5
4
3
2
1
0
Precoating cores with Kollidon VA 64
Uncoated cores
0 100 200 300 400 500 600 700 800
Days
COATING SYSTEMS 1021
FIGURE 26 Water absorption of precoating and uncoated cores of combinated dextran –
HPMC matrix tables.
coating. The copovidone (i.e., Kollidon VA 64) not only increases the mechanical
properties of the tablet (less friability) but also prevents the amount of water
absorbed from the air in tropical and subtropical stability conditions (25 and 75%
relative humidity).
Figure 26 shows a comparative study of uncoated tablet and sugar - coated tablet
after a barrier to water with copovidone 0.5 mg/cm 2 of the warm tablet cores using
a 10% solution in ethanol. During two years the coating tablets (with initial humidity
2.5%) remained stable and dissolution profi les were similar to the initial time
with similarity f 2 = 82 observed and friability decreased from 0.25% (uncoated
cores) to 0.02% (coated tablets).
Similar results are reported in the literature when Kollidon VA 64 is compared
to povidone (Kollidon K 25, K 30, and 90 F). Copovidone absorbs about three times
less water than the other soluble Kollidon K 25, 30, and 90F after seven days at
25 ° C up to 80% relative humidity [62] . Kollidon VA 64 is manufactured by free -
radical polymetization of 6 parts of vinylpyrrolidone and 4 parts of vinyl acetate in
2 - propanol. A water - soluble copolymer with a chain structure is obtained. In contrast
to the soluble grades of Kollidon, the number 64 is not a K value but the mass
ratio of the two monomers, vinylpyrrolidone and vinyl acetate. The K
value of
Kollidon VA 64 is of the same order of magnitude as that of Kollidon 30. Synonyms
for Kollidon VA 64 are copovidone, copovidonum, copolyvidone, copovidon, and
PVP - VAc - copolymer [Eur. Ph., Japanese Pharmaceutical Excipients, and USP
National Formulary (NF)] [63] .
Copovidone forms soluble fi lms independently of the pH value, regardless of
whether it is processed as a solution in water or in organic solvents. He offers better
plasticity and elasticity than other povidones. On the other hand, fi lms are also less
tacky. Kollidon VA 64 usually absorbs water, and it is seldom used as the sole fi lm -
forming agent in a formulation. Normally it is better to combine it with less hygroscopic
substances such as cellulose derivates [54] , shellac, polyvinyl alcohol (PVA),