Pharmaceutical Technology: Controlled Drug Release, Volume 2

92 CH. 8] TOPICAL RELEASE AND PERMEATION STUDIES
Table 1—Formulations
a Formulation A was also made at 0.5%, 2% and 3% concentration of drug.
stability of drug was determined in the buffer solution. After 24 h at 37°C no potency loss was
noted.
Content uniformity
All samples prepared were analysed for propranolol hydrochloride content. Only samples with
100% ±10% drug contents were used in these studies.
IN VITRO DIFFUSION STUDIES
The in vitro diffusion studies for each sample were carried out by using the Franz diffusion cells
with a diffusional area of about 1.76cm 2 . The acceptor compartment of the apparatus was filled
with the buffer solution pH 6, USP [21], and maintained at 37±0.5°C via a circulating water
system. The diffusion membrane (the cellulose membrane with a molecular weight cut-off point
of 1000 or the hairless mouse skin) previously prepared was placed between the donor and the
acceptor compartments of the assembly. An accurately weighed 4g of sample was then placed in
the donor cell and the diffusion process was started. The solution in the acceptor compartment
was continuously stirred with a small magnetic stirrer to maintain the sink conditions. Aliquots
from the receptor cells were removed at 0.5, 2, 4, 8 and 24 h time intervals and replaced with equal