Ocular Hypertension and Glaucoma
Dorzolamide ophthalmic solution is used topically to reduce elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. Dorzolamide hydrochloride and timolol maleate in a fixed-combination ophthalmic solution is used topically to reduce elevated IOP in patients with open-angle glaucoma or ocular hypertension who have not responded adequately (i.e., failed to achieve target IOP as determined after multiple measurements over time) to a topical β-adrenergic blocking agent. While the exact role of dorzolamide in the management of patients with elevated IOP remains to be determined, the drug is used as monotherapy when a topical β-adrenergic blocking agent or sympathomimetic agent, or latanoprost cannot be used because of intolerance or a contraindication. In addition, dorzolamide is useful as a first-line ''add-on'' agent when more than one drug is needed. The manufacturer states that topical dorzolamide has not been evaluated in patients with angle-closure glaucoma. Although dorzolamide has been used in a limited number of patients with glaucoma or ocular hypertension associated with pseudoexfoliation syndrome, further study is needed to evaluate the use of the drug in this condition.
Dorzolamide is effective in reducing IOP when used alone or in conjunction with other ocular hypotensive agents. Safety and efficacy of dorzolamide was evaluated in a multicenter, randomized, double-blind, active-controlled study that included several hundred patients with baseline IOP values of 23 mm Hg or higher. Patients were randomized to receive dorzolamide ophthalmic solution 2% three times daily, timolol ophthalmic solution 0.5% twice daily, or betaxolol ophthalmic solution 0.5% twice daily. In this study, dorzolamide was as effective as betaxolol in reducing IOP in patients with glaucoma or ocular hypertension; dorzolamide and betaxolol were less effective than timolol in reducing IOP. At 1 year, treatment with dorzolamide, timolol, or betaxolol produced a mean reduction in IOP of 4.3-6.2, 5.4-7.1, or 4-5.7 mm Hg from baseline, respectively. These IOP reductions correspond to a mean peak reduction of IOP of 23, 25, or 21% from baseline in patients receiving dorzolamide, timolol, or betaxolol, respectively, and a mean trough reduction of IOP of 17, 20, or 15%, respectively.
When dorzolamide is used in conjunction with a topical β-adrenergic blocking agent (e.g., betaxolol, timolol), the IOP-lowering effects of these agents may be additive. In one study in patients with open-angle glaucoma or ocular hypertension in whom IOP was not adequately controlled with timolol or betaxolol alone (i.e., IOP value remained at 22 mm Hg or higher, or monotherapy with timolol or betaxolol resulted in less than a 15% reduction of IOP from baseline), concomitant administration of dorzolamide 2% twice daily resulted in further decreases in IOP of about 15-25%. In patients with open-angle glaucoma or ocular hypertension receiving dorzolamide 2% three times daily in whom IOP was not adequately controlled (i.e., IOP value remained at 22 mm Hg or higher, or therapy with dorzolamide resulted in less than a 15% reduction of IOP from baseline), concomitant administration of timolol 0.5% twice daily resulted in further decreases in IOP of about 16-20%. While therapy with dorzolamide in fixed combination with timolol twice daily is associated with greater decreases in IOP than monotherapy with dorzolamide 2% three times daily or timolol 0.5% twice daily, therapy with dorzolamide 2% three times daily in combination with timolol 0.5% twice daily is associated with a slightly greater decrease in IOP (1 mm Hg) than the twice-daily regimen of dorzolamide in fixed combination with timolol. In patients with glaucoma or ocular hypertension receiving timolol 0.5% twice daily, concomitant administration of dorzolamide 2% two or three times daily produced similar IOP-lowering effects compared with concomitant administration of pilocarpine 2% four times daily; in addition, add-on therapy with dorzolamide was better tolerated than add-on therapy with pilocarpine.
Studies to date indicate that tolerance to dorzolamide does not occur and that the reduction in mean IOP is maintained over at least 12 months after initial stabilization.
Inhibition of Perioperative IOP Increases
Topical dorzolamide has been used prophylactically before neodymium yttrium aluminum garnet (Nd:YAG) lasar posterior capsulotomy. Results of a randomized controlled study indicate that administration of 1 drop (20 mcL) of dorzolamide 2% 1 hour prior to capsulotomy is more effective in preventing postoperative increases in IOP than placebo and as effective as oral acetazolamide 125 mg administered 1 hour prior to the procedure.