Pharmacological Therapy for Glaucoma

Abstract

For some time the medical treatment of glaucoma has consisted of topical β-blockers, adrenergic agents, miotics and oral carbonic anhydrase inhibitors (CAIs). However, the therapeutic arsenal available for the medical treatment of glaucoma has recently extended with new classes of ocular hypotensive agents i.e. prostaglandins, local CAIs and α₂-adrenergic agents. β-Blockers are still the mainstay in glaucoma treatment and are first line drugs. However, even if they are applied once daily, as with timolol in gel forming solution and levobunolol, the possible cardiopulmonary adverse effects of β-blockers remain a cause for concern. When mono therapy with β-blockers is ineffective in reducing intraocular pressure (IOP) or is hampered by adverse effects, a change of monotherapy to prostaglandins, local CAIs, (X2-adrenergic agonists (brimonidine) or to dipivalyl epinephrine is advised. Prostaglandins, local CAIs and (X2-adrenergic agonists, such as brimonidine, may in time become first line drugs because they reduce IOP effectively and until now systemic adverse effects have rarely been reported with these agents. The development of a pro-drug of either a local CAI or an α₂-adrenergic agonist with a sustained and continuous effect on IOP level, which could be applied once a day is suggested. Because of these new developments, miotics, i.e. pilocarpine and carbachol, are recommended as second or third line drugs. The cholinesterase inhibitors are considered third line drugs as better agents with fewer local and systemic adverse effects have become available. Oral CAIs may be used temporarily in patients with elevated IOPs e.g. post-surgery or post-laser, or continuously in patients with glaucoma resistant to other treatment. Combining ocular hypotensive drugs is indicated when the target pressure for an individual patient cannot be reached with monotherapy. Combination therapy of β-blockers is additive with prostaglandins, topical CAIs and miotics. Prostaglandins such as latanoprost can be combined with β-blockers, adrenergic agents, local CAIs and miotics. Combinations with brimonidine or local CAIs need further investigation. Treatment of glaucoma with the new ocular hypotensive agents, either in monotherapy or combination therapy, may provide lower IOPs and delay or postpone the need for surgery.