چکیده (انگلیسی):

The purpose of the present study was to investigate incorporation
of hydrophobic (ie, waxy) material into pellets using
a thermal sintering technique and to evaluate the pellets in
vitro for controlled release. Pellets prepared by extrusionspheronization
technology were formulated with a watersoluble
drug, microcrystalline cellulose, and carnauba wax.
Powdered carnauba wax (4%-20%) prepared by grinding or
by emulsification was studied with an attempt to retard the
drug release. The inclusion of ground or emulsified carnauba
wax did not sustain the release of theophylline for more
than 3 hours. Matrix pellets of theophylline prepared with
various concentrations of carnauba wax were sintered thermally
at various times and temperatures. In vitro drug release
profiles indicated an increase in drug release retardation
with increasing carnauba wax concentration. Pellets prepared
with ground wax showed a higher standard deviation than did
those prepared with emulsified wax. There was incomplete
release at the end of 12 hours for pellets prepared with 20%
ground or emulsified wax. The sintering temperature and duration
were optimized to allow for a sustained release lasting
at least 12 hours. The optimized temperature and duration
were found to be 100°C and 140 seconds, respectively. The
sintered pellets had a higher hydrophobicity than did the
unsintered pellets. Scanning electron micrographs indicated
that the carnauba wax moved internally, thereby increasing
the surface area of wax within the pellets.