Permeability of human cornea and sclera to sulfonamide carbonic anhydrase inhibitors
H. F. Edelhauser and T. H. Maren
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
Corneal penetration of sulfonamide carbonic anhydrase inhibitors for
topical treatment of glaucoma has been tested in human eye bank and rabbit
tissue. Paired corneas, with the epithelia intact or removed, and excised
sclera were perfused in vitro. Corneal permeability (Kp) to methazolamide
and ethoxzolamide was similar in both species, but for benzolamide and
bromacetazolamide the Kp was greater in humans. Human corneas without
epithelium had Kp the same as scleral Kp. Topical methazolamide (6 mmol/L)
was studied in vivo in rabbits and in ten humans before cataract surgery.
The mean (+/- SE) concentration in the rabbit aqueous was 3.2 +/- 1.4
mumol/L at eight minutes and 1.2 +/- 0.16 mumol/L at one hour. In humans,
less than 0.2 mumol/L was detected at eight minutes; at one hour none was
detected in three cases, and 0.4 +/- 0.08 mumol/L was detected in four
cases. Lower permeability in humans than rabbits may result from a fourfold
greater blinking rate, a twofold greater tear turnover, and a twofold lower
corneal/conjunctival area.
