Abstract
The xanthan/chondroitin sulfate (X/CS) hydrogels, obtained by a crosslinking technique, were evaluated in vitro and in vivo as matrices for theophylline release. The influence of pH of simulated physiological media on the X/CS swelling behaviour at 37°C was investigated. The hydrogels theophylline loading degree was evaluated by near infrared chemical imaging (NIR-CI) technique and confirmed also by FT-IR spectroscopy; the drug loading was about 77.5% based on PLS-DA prediction (Partial least squares-Discriminate Analysis). The release profiles of theophylline from X/CS hydrogels in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) depend on CS content. The release mechanisms were controlled by the drug solubility and ionic properties of the polymers. In vivo theophylline delivery was done by oral administration. Pharmacokinetic analysis revealed sustained-release characteristics for 50/50 X/CS theophylline-loaded formulation compared with raw theophylline which was rapidly absorbed, distributed and eliminated. A good in vitro-in vivo correlation was found.
Highlights
Sustained release dosage forms extend the duration time of drug therapy, reduce side-effects and increase safety and patient compliance by reducing the frequency of dosing
Time to reach the maximum swelling degree, in simulated gastric fluid (SGF), varies from 14 minutes in case of xanthan-based matrix with a degree of swelling about 727% to 6 minutes for composition 70/30 xanthan/chondroitin sulfate (X/Chondroitin sulfate (CS)) with a degree of swelling of 900%, the process being much faster for the composition 50/50 X/CS with a maximum swelling degree of 1363% recorded in about 2 minutes (Table 1)
Swelling of the xanthan/chondroitin sulfate matrix in acidic and buffer solutions showed that the ionic strength of the liquid has a strong effect on the sorptive properties of the matrix
Summary
Sustained release dosage forms extend the duration time of drug therapy, reduce side-effects and increase safety and patient compliance by reducing the frequency of dosing. Multiple daily administration of an immediate release dosage form results in patient non-compliance. To control and modulate drug release properties of drugs, retardant polymers including hydrophilic polymers such as chitosan, chondroitin sulfate, xanthan and other polysaccharides have been utilized in dosage forms. The hydrophilic polymers control drug release from dosage forms by hydrogelation. The retardation mechanism is based on the intramolecular hydrogelation of a hydrophilic polymer during swelling and can be affected by the ionic strength of the dissolution medium. It is well known that the pH of the gastrointestinal tract (GI tract) varies from pH 1 to 3 in the stomach and increases to approxi-
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