No abstract

No abstract

The oral absorption of theophyll ine 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 i n v i v o 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. pH dependent release behavior o f the alginate formulation is explained. gel behaviors in these two polymers are discussed. The relative oral bioavailabilities of these two formulations in dog were 74-The Drug release mechanisms which are influenced by the 84% compared to immediately releasing capsules, and three-fold that of the commercial product with an equivalent dose.

No abstract

A polymer carrier system was developed to reduce the bitterness of erythromycin and its 6-O-methyl derivative, clarithromycin, by absorption to Carbopol. The mechanism involves ionic bonding of the amine macrolide to the high molecular weight polyacrylic acid, thereby removing the drug from the solution phase in an ion-free suspension. After ingestion, endogenous cations displace the drug from the polymer in the gastrointestinal tract to achieve bioavailability. The macrolide-Carbopol complexes were prepared by dissolving or slurrying predetermined ratios of drug and polymer in water or hydroalcoholic mixtures. A series of in vitro equilibrium studies, taste screening, and bioavailability studies in dogs established the characteristics for the various drug-polymer ratios. Taste protection was further improved by encapsulating the adsorbate particles with polymer coatings. Hydroxypropyl methylcellulose phthalate (HP-55) provided the best combination of suspension stability, taste protection and bioavailability. Human bioavailability studies demonstrated that the microencapsulated Carbopol absorbates of erythromycin and clarithromycin gave blood levels comparable to those obtained from conventional solid formulations.