topical ophthalmic suspensions containing tobramicin and dexamethasone

摘要

topical ophthalmic suspensions containing tobramicin and dexamethasone. The present invention relates to ophthalmic pharmaceutical compositions containing tobramycin, dexamethasone and deacetylated xanthan gum. The compositions provide longer ocular retention for enhanced ocular bioavailability of tobramicin and dexamethasone. In a preferred embodiment, the compositions also provide improved suspension of dexamethasone. The concentration of ionizable species in the compositions is controlled to prevent precipitation of xanthan gum as a result of ionic interactions between tobramicin and xanthan gum, while permitting a restoration of viscosity upon topical application of the compositions to the eye. The use of deacetylated xanthan gum is disclosed so as to avoid formulation instability caused by pH change during storage.