The first topical carbonic anhydrase inhibitor for clinical use Dorzolamide HCl (Axon 1517) has been prescribed widely for the treatment of glaucoma and ocular hypertension. It inhibits carbonic anhydrase II (CA-II; EC 22.214.171.124) selectively, which is the main CA iso-enzyme involved in aqueous humor secretion. Inhibition of CA-II in the ciliary processes of the eye decreases aqueous humor secretion, presumably by slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport. Dorzolamide also accumulates in red blood cells as a result of CA-II binding, as CA-II is found predominantly in erythrocytes. However, sufficient CA-II activity remains so that adverse effects due to systemic CA inhibition are not observed.
 Dorzolamide. A review of its pharmacology and therapeutic potential in the management of glaucoma and ocular hypertension. J.A. Balfour, M.I. Wilde. Drugs Aging. 1997, 10, 384-403.