N. Realdon et al., EFFECTS OF SILICIUM DIOXIDE OIL DRUG-RELEASE FROM SUPPOSITORIES, Drug development and industrial pharmacy, 23(11), 1997, pp. 1025-1041
Silica gel is frequently introduced into lipophilic excipients for sup
positories as a viscosity agent, to, prevent drug sedimentation in the
melted mass, and to decrease release rate. The effect of silica gel (
Aerosil 200) concentration on the availability of some drugs frequentl
y used in suppositories in different unitary doses was studied. When s
ilica gel concentration in the excipient was increased, a decrease in
aminophylline and aminophenazone release rate was observed. Paracetamo
l in small unitary doses has shown a tendency to increase release rate
at higher silica gel concentrations. This behavior was even more evid
ent in suppositories containing promethazine hydrochloride, while for
those containing benzydamine hydrochloride the increase in release rat
e with increasing silica gel concentration was evident for all drug do
ses. However, the behavior was a consequence of the trend of supposito
ry viscosity during drug release. As a consequence of both the drug an
d silica gel being discharged, the viscosity progressively decreased w
ith an increased silica gel concentration. The effect on drug availabi
lity was conditioned by silica gel concentration, as well as the type
and dose of the drug, which could act on the shape of the suppository
inner structure that is responsible for viscosity and mobility of drug
particles.