Drug and mucilage mixture.
Mucilage matrices contained diclofenac sodium of the optimized batch (HL6) in proportions of 1:2 of the drug to mucilage,
respectively. Figure 3 shows the percentage increase in weight resulting from water uptake in distilled water at various agitation
speeds. No significant differences in weight gain (i.e., water uptake) between matrices containing the drug at the two different
agitation speeds were observed. The only significant differences in weight gain were shown for matrices containing different
proportions of mucilage. Matrices containing a lower proportion of mucilage (1:1) showed a lower degree of weight gain with
time. This result is expected because the lower proportion of mucilage would decrease the ability of the matrix to absorb
water. The dynamic balance between weight gain resulting from water uptake and weight loss resulting from mucilage erosion
and drug dissolution was further illustrated by the profiles for mucilage matrices containing diclofenac sodium at both agitation
speeds. Figure 4 shows the percentage of erosion into distilled water at two agitation speeds. An initial rapid uptake of
water by the dry matrices occurred during the first 2 h, followed by a leveling off of the wet weights because of the increasing
rate of erosional release at 100 rpm. This condition persists until the rate of erosion exceeded the rate of water uptake,
with a resultant decrease in weight with time.
Table VI shows the results of the radial and axial study. The data show that the increase in diameter and thickness was proportionate
with time. More swelling, however, occurred in the axial direction compared with the radial direction.
To study the effect of storage on in vitro drug release, a stability study of the best formulation (HL6) was carried out at 40 °C and 75% relative humidity in a humidity
oven. Samples were withdrawn after a three-month interval and in vitro drug release was carried out. No change in the in vitro drug release pattern occurred. The value of the similarity factor was 82.14, which indicated a good similarity of dissolution
profile before and after stability studies. The calculated t-value (0.997) was smaller than the tabulated value (2.577), which indicated an insignificant difference in the dissolution
profile before and after the stability study.
Table VI: Radial and axial swelling study of optimized batch (HL6).
The authors conclude that a novel hydrophilic excipient, such as mucilage extracted from Hibiscus rosa-sinensis Linn, can be used for the development of sustained-release tablets. The dried mucilage powder shows superior swelling capacity
and is pH independent. The mucilage can be further explored as a disintegrating agent, gelling agent and modified-release
Girish K. Jani, PhD,* is a principal at K.B. Raval College of Pharmacy at Sheratha Post Kasturinagar, Gandhinagar, Gujarat, India 382423, tel.+
91 793 252 9996, fax +91 792 928 9767, firstname.lastname@example.org
Dhiren P. Shah is an assistant professor at C.K. Pithawala Institute of Pharmaceutical Science and Research, Surat, India.
* To whom correspondence should be addressed.
Submitted: Apr. 6, 2007. Accepted May 24, 2007.