Drug delivery systems which yield ideal treatments are currently the center of interest for
researchers. Niosomes have numerous advantages over other drug delivery systems. However, stability
issue is not clear yet and is a serious drawback for niosomes. In this study, the stability of niosomes
was the center of interest. Piroxicam which was chosen as the model drug was loaded to niosomes.
Niosomes were prepared by thin-film method and different forms (aqueous dispersion, lyophilized
powder and lyophilized powder with cryoprotectant) of the original niosome formulation were prepared.
The samples were stored either at 5°C±3°C or 25°C±2°C/60% RH±5% RH for 3 months. The drug leakage percent,
particle size and distribution, zeta potential, drug release profiles were determined and niosomes were visualized under
optic microscope. Niosome formulation provided sustained release of piroxicam. The drug leakage from stored niosomes
was observed at the level of 1.56-6.63 %. Individual vesicle images were obtained for all samples by optical microscope.
However, particle size of niosomes was increased upon storage. The zeta potential values were neither related to time nor
physical form. Drug release profiles and amounts were quite similar for all forms of niosomes and the original formulation
but a slight decrease was noticed on drug release amounts by time. This indicates that niosomes become more rigid by
time. Although the ideal storage was obtained with lyophilized niosomes at 5±3°C in this study, the usage of suitable
cryoprotectant and optimized lyophilization process should be further evaluated.
Keywords: Drug release, lyophilization, niosomes, piroxicam, span 40, stability.
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