Pharmaceutical Technology: Controlled Drug Release, Volume 2

96 CH. 8] TOPICAL RELEASE AND PERMEATION STUDIES
Table 5—Drug release from Methocel® matrix formulation containing varied concentrations of propranolol
hydrochloride
Average of three determinations.
Fig. 2—Effect of drug loading on the release profile of propranolol hydrochloride from Methocel ® matrix: , 3.0%;
, 2.0%; □, 1.0%; ○, 0.5%.
DMSO in an effort to enhance drug release through the hairless mouse skin. When the diffusion
membrane itself was soaked with DMSO for 1 h prior to its use, the drug release-permeation was
increased by 40% (Table 6 and Fig. 3). The release patterns of the drug were linear from the
samples containing in some way small amounts of DMSO. The sample without DMSO provided
linear release only up to the first 12 h period of the study. This could be attributed to the
complicated processes involved in the passive diffusion of the drug through the skin. The linear
release suggest that the drug release was zero order.
Using these data, some of the related parameters, i.e. rate constant (K), correlation coefficient
(r) and the values for the Y intercepts, were calculated (Table 7). Comparing these data