Corneal and scleral penetration studies of 6-hydroxyethoxy-2-benzothiazole sulfonamide: a topical carbonic anhydrase inhibitor.

A newly synthesized topical carbonic anhydrase inhibitor, 6-hydroxyethoxy-2-benzothiazole sulfonamide (6-HS), was used as a model drug to determine its corneal and scleral permeabilities in rabbit eyes. The corneal permeability coefficient of 6-HS for short duration glaucoma and normal rabbit eye was not significantly different (its mean value was around 2.9 x 10(-6) cm/sec), while the corneal permeability coefficient for long duration glaucoma rabbit eye was 1.8 times greater than that for the normal eye. The sclera was found to have a higher permeability than the cornea in that after four hours perfusion the amount of drug which passed through the sclera was 11 times greater than that of the cornea. In addition, it was also noted that after topical instillation of 50 microL of 3% 6-HS gel the aqueous humor concentrations of 6-HS in short duration glaucoma eye and normal eye were not statistically different.