**3.7 Dissolution rate studies**

The dissolution curves of pure carvedilol and its spherical crystals in 0.1 N HCl (pH 1.2) are shown in fig. 7. The release rate profiles were expressed as the percentage drug released vs. time. Table 4 shows % drug dissolved in 1h (DP60) and dissolution efficiency values at 30 min (DE30) for carvedilol and its spherical crystals. These values are tested statistically through one way ANOVA and are found significantly different (p<0.05) from pure carvedilol. As indicated carvedilol was dissolved more than 80% from spherical crystals CP681, CP1271 and CP1272 after 1h and more than 90% from spherical crystal CP682 while the pure CAR powder was just dissolved 34.37% at comparable time. The results revealed that the spherical crystals caused significant increase (P<0.05) in drug release compared to the pure drug. Enhancement in dissolution rate of spherical agglomerates as compared to pure drug may be due the presence of hydrophilic polymer, Poloxamer. The mechanism


aMean ± SD, n = 3

bSignificantly different compared to carvedilol (*p* < 0.05).

Table 4. Drug Release and Dissolution Efficiencya

Fig. 7. Dissolution profile of CAR and its agglomerates. (Mean ±SD, n = 3.)

behind the greater solubility and dissolution of CAR from its agglomerated form may resemble the solid dispersion mechanism despite the larger particle size of agglomerates. This effect may be due to improved wettability of the surface of agglomerates by the adsorption of poloxamer onto the surfaces of crystals. These results confirm that the dissolution rate of carvedilol was increased in form of spherical crystals when compared to its pure form.
