Topical ophthalmic suspensions containing tobramycin and dexamethasone

摘要

Ophthalmic pharmaceutical compositions containing tobramycin, dexamethasone and deacetylated xanthan gum are described. The compositions provide longer ocular retention for enhanced ocular bioavailability of tobramycin and dexamethasone. In a preferred embodiment, the compositions also provide for improved suspension of dexamethasone. The concentration of ionizable species in the compositions is controlled so as to prevent precipitation of the xanthan gum as a result of ionic interactions between tobramycin and xanthan gum, while allowing for 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 drift during storage.