Comparison of ophthalmic beta-blocking agents.
Glaucoma is described, and the chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of betaxolol and levobunolol in comparison with timolol are reviewed. Betaxolol and levobunolol are two beta-adrenergic blocking agents being marketed as ophthalmic solutions for treatment of primary open-angle glaucoma (POAG) and ocular hypertension (OHT). Betaxolol is a relatively cardioselective beta-adrenergic blocker, while levobunolol is a nonselective beta-adrenergic blocking agent. Double-blind comparative trials have suggested that betaxolol has an equal to slightly lower efficacy and levobunolol has equal efficacy in reducing intraocular pressure (IOP) compared with timolol, the first ophthalmic beta blocker. A mean reduction in intraocular pressure of 15-35% occurs with both betaxolol and levobunolol and is reported to be maintained with prolonged use. Betaxolol is associated with a higher (25%) incidence of local ocular adverse reactions than timolol. However, betaxolol produces less systemic beta 2- and possibly beta 1-adrenergic receptor blockade than either timolol or levobunolol. Betaxolol may be relatively safer to use in patients with reactive airway disease than either timolol or levobunolol. Levobunolol causes a similar to greater incidence of local ocular adverse reactions and similar systemic beta blockade compared with timolol. Levobunolol may possibly be longer acting than timolol, allowing more patients to be controlled by once-daily dosing. Betaxolol and levobunolol appear to be similar to timolol in controlling IOP in patients with POAG and OHT; additional experience with these agents is needed to assess the advantages and disadvantages of each agent.
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