Oral sustained delivery of theophylline from thermally reversible xyloglucan gels in rabbits

Thermally reversible gels formed in-situ following the oral administration of dilute aqueous solutions of an enzyme-degraded xyloglucan to rabbits wer e evaluated as sustained-release vehicles for the delivery of theophylline. In-vitro release of theophylline from gels formed by warming xyloglucan so ls (0.5, 1.0 and 1.5% w/w) to 37 degreesC followed root-time kinetics over a period of 4 h. Gels formed after oral administration to rabbits of chille d 1.5% w/w aqueous solutions of xyloglucan containing dissolved drug showed sustained-release characteristics with a maximum plasma concentration at 4 .5 h. The theophylline bioavailability from a 1.5% w/w xyloglucan gel was 1 .7-2.5 times that of commercial oral sustained-re lease liquid dosage forms containing an identical theophylline concentration. It was concluded that dilute solutions of the enzyme-degraded xyloglucan had suitable rheological properties and in-situ gelling characteristics for use as sustained-releas e vehicles for oral drug delivery. The in-vivo release characteristics of t heophylline in a rabbit model suggested the potential for the use of these vehicles in humans for the oral delivery of this drug.