Abstract
Gels formed in situ following oral administration of aqueous solutions of sodium alginate to rabbits were evaluated as sustained-release vehicles. The formulation contained calcium ions in complexed form, the release of which in the acidic environment of the stomach caused gelation of the sodium alginate. Plasma levels of theophylline after oral administration of sodium alginate and a commercial oral sustained-release liquid dosage form were compared in rabbits. Bioavailability of theophylline from sodium alginate gels formed by in situ gelation in the animal stomach was increased by 3-fold in rabbits compared with that from the commercial oral formulation. There was no significant difference in the mean residence times of theophylline when administered by these two vehicles.
