Table V: Summary of ANOVA for the response parameters of the model formulations of dispersible tablets prepared as per 23
factorial design. All figures are courtesy of the authors.
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The physical properties and response parameters of the different batches of model formulations are listed in Table III and
Table IV, respectively. The disintegration time, percentage friability, weight, and content uniformity complied with official
specifications.
Figure 4: 3-D plots showing the effect of formulation variables on disintegration time of tablets containing (a) nabumetone,
and (b) nabumetone b-cyclodextrin complex. All figures are courtesy of the authors.
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Disintegration time.
The results of the analysis of variance along with the mathematical models generated are summarized in Table V. The DT of
various model formulations ranged from 35 ± 0.83 to 120 ± 0.63 and depended on the bicarbonate and crospovidone levels. The
linear model generated for DT was significant with an F value of 537 (p, 0.0001) and an R2 value of 0.999. The negative influence of the levels of ammonium bicarbonate and crospovidone on DT was clearly evident
in the three-dimensional plots (see Figure 4).
DT decreased from 112.33 ± 3.44 s to 72.66 ± 2.78 s and from 91.33 ± 3.16 s to 35 ± 2.54 s at lower and higher levels of crospovidone,
respectively, as the levels of bicarbonate increased in tablets containing the drug (see Figure 4a). This decrease in DT
occurs because higher levels of subliming agent render the tablet more porous, which permits the water to contact with the
disintegrant quickly, thereby causing rapid tablet disintegration. Reduction in DT with increase in the amounts of subliming
agent has been reported previously when camphor was used as a subliming agent (25).
The plot illustrates that DT decreased from 112.33 ± 3.44 s to 91.33 ± 3.16 s and from 72.66 ± 2.78 s to 35 ± 2.54 s at lower
and higher levels of bicarbonate, respectively, as the crospovidone increased. The three-dimensional plot revealed that the
effects of bicarbonate and crospovidone on DT were more pronounced at higher levels. This result could be attributed to quick
water uptake and rapid swelling of the super disintegrant at higher levels. A reduction in the DT of orodispersible tablets
with an increase in the levels of crospovidone has been cited in the literature (26). The corresponding contour plots depict
a nonlinear relationship between the two variables on DT and suggests that the DT can be minimized using high levels of subliming
agent and disintegrant.
DT decreased from 121.66 ± 4.52 to 81.33 ± 3.78 s and from 99.66 ± 4.12 s to 41.33 ± 2.14 s at lower and higher levels of
crospovidone, respectively, as the levels of bicarbonate increased in tablets containing the complex (see Figure 4 b). The
plot also shows that DT decreased from 121.66 ± 4.52 s to 99.66 ± 4.12 s and from 81.33 ± 3.78 s to 41.33 ± 2.14 s at lower
and higher levels of bicarbonate, respectively, as the levels of crospovidone increased. In addition to the main effects,
the interaction effect X1X2 had a negative influence on DT.
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