XANTHAN GUM AND ALGINATE BASED CONTROLLED RELEASE THEOPHYLLINE FORMULATIONS

The oral absorption of theophylline from two sustained release formulations, formulated using xanthan gum or sodium alginate, has been investigated in the beagle dog. A commercial product was used for comparison. Dissolution tests and an in vivo dog study both indicated that the xanthan gum tablet released drug at a constant rate and performed as a pH independent zero-order controlled release formulation. With the alginate tablet, faster dissolution rates were observed when acid medium was present. The pH dependent release behavior of the alginate formulation is explained. Drug release mechanisms which are influenced by the gel behaviors in these two polymers are discussed. The relative oral bioavailabilities of these two formulations in dog were 74-84% compared to immediately releasing capsules, and three-fold that of the commercial product with an equivalent dose.