Dorzolamide (
dorzolamide hydrochloride), the first topical
carbonic anhydrase (CA) inhibitor to become available for clinical use, lowers intraocular pressure (IOP) by reducing aqueous humour formation. It is formulated
as a 2%
eyedrop for use in the management of
glaucoma and
ocular hypertension. When administered 3 times daily,
dorzolamide is effective in lowering IOP in patients with
open-angle glaucoma or
ocular hypertension. Mean IOP was reduced by approximately 4 to 6 mm Hg at peak (2 hours postdose) and 3 to 4.5 mm Hg at trough (8 hours postdose) in clinical trails. A 1-year comparative study showed that the ocular hypotensive efficacy of dorzolamine 2% 3 times daily was similar to that of
betaxolol 0.5% twice daily, but slightly inferior to that of
timolol 0.5% twice daily.
Dorzolamide has additive ocular hypotensive effects when used in conjunction with topical
beta-adrenergic antagonists and was as effective as
pilocarpine 2% 4 times daily as adjunctive
therapy in patients receiving
timolol.
Dorzolamide does not appear to produce the
acid-base or
electrolyte disturbances and severe systemic adverse events associated with oral CA inhibitors, and unlike
beta-adrenergic antagonists, it is not contraindicated in patients with
asthma, reactive airways disease or
heart disease. Furthermore, as CA inhibitors do not cause
miosis, they may cause less interference with vision than
pilocarpine or
epinephrine (
adrenaline). The most common adverse effects associated with
dorzolamide are bitter taste and transient local burning or stinging.
Conjunctivitis was the most common reason for discontinuation of
dorzolamide in one large study. Thus, available data suggest that
dorzolamide has potential as an alternative
therapy option in patients with
glaucoma or
ocular hypertension who are intolerant of, or unable to receive, ophthalmic
beta-adrenergic antagonists and as adjunctive
therapy in patients already receiving these agents. Further efficacy and tolerability data are needed to determine the place of
dorzolamide in
therapy.