Ocular Hypertension and Glaucoma
In ophthalmology, topical timolol is used to reduce elevated 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. Topical timolol also has been used to reduce elevated IOP in patients with aphakic glaucoma and some secondary glaucomas. Elevated IOP presents a major risk factor in glaucomatous visual field loss; the higher the level of IOP, the greater the likelihood of optic nerve damage and glaucomatous visual field loss. Current data from a limited number of controlled studies suggest similar clinical efficacy for ophthalmic timolol maleate and ophthalmic timolol as the hemihydrate.
Timolol may be used alone or in conjunction with a topical miotic (e.g., pilocarpine), latanoprost and/or a topical or systemic carbonic anhydrase inhibitor. When used in conjunction with these agents, timolol may have an additive IOP-lowering effect. While therapy with timolol in fixed combination with dorzolamide twice daily is associated with greater decreases in IOP than monotherapy with timolol 0.5% twice daily or dorzolamide 2% three times daily, therapy with timolol 0.5% twice daily in combination with dorzolamide 2% three times daily is associated with a slightly greater decrease in IOP (1 mm Hg) than the twice-daily regimen of timolol in fixed combination with dorzolamide. If timolol is used to reduce IOP in patients with angle-closure glaucoma, the drug should not be used alone but rather in combination with a topical miotic since timolol has little or no effect on pupil size.
Like levobunolol, timolol reduces elevated IOP in patients with chronic open-angle glaucoma without producing the miosis and/or ciliary spasm that are associated with miotic agents. In double-blind studies in patients with open-angle glaucoma, usual doses of timolol have been found to be at least as effective as therapeutic doses of pilocarpine in reducing elevated IOP without the miosis, ocular irritation, and blurred vision associated with pilocarpine therapy. Timolol maleate also has been found in multiclinic studies to be at least as effective as epinephrine in reducing IOP in patients with open-angle glaucoma. Like other ophthalmic nonselective β-blocking agents (e.g., levobunolol), ophthalmic timolol has been associated with adverse systemic pulmonary and cardiovascular effects. The drug should be used with caution in patients with diminished pulmonary function, and is contraindicated in patients with asthma or a history of asthma and in patients with severe chronic obstructive pulmonary disease. Following prolonged therapy with topical timolol, the effect in reducing IOP is generally well maintained, but tolerance has been reported in some patients. In one long-term study in patients receiving timolol for at least 3 years, the reduction in mean IOP was maintained following initial stabilization with the drug.
For systemic uses of timolol maleate, see 24:24.