Oral sustained delivery of theophylline using in-situ gelation of sodium alginate.

Gels formed in situ following oral administration of aqueous solutions of sodium alginate (1.0-2.0%w/v) to rats were evaluated as sustained release vehicles for the delivery of theophylline. The liquid formulation contained calcium ions in complexed form, the release of which in the acidic environment of the stomach caused gelation of the alginate. Bioavailability of theophylline from alginate gels formed by in situ gelation in the rat stomach was increased by 1.3-2-fold in rats for alginate concentrations of 2.0 to 1.0%w/v respectively compared with that from a proprietary oral sustained release formulation containing an identical drug concentration. There was no significant difference in the mean residence times of theophylline when administered by these two vehicles.