11.6 Treatment of glaucoma
Timolol 0.25%, 0.5% (eye drops, preservative-free unit dose eye drops) is recommended for first-line use. It is a non-selective beta-adrenoceptor blocking drug with no sympathomimetic activity. A long acting preparation of timolol is available as Timoptol®-LA 0.25%, 0.5% (eye drops) which allows once daily administration.
Carteolol 1% (eye drops) is an alternative beta-adrenoceptor blocking drug. It is not cardioselective but has intrinsic sympathomimetic activity.
Pilocarpine 1%, 2%, and 4% (eye drops) is a miotic and so should be avoided where pupillary constriction is undesirable. It may also cause ciliary spasm which may lead to blurring of the vision and brow-ache.
Acetazolamide 250mg (tablets, m/r capsules) may be used in conjunction with eye drop regimens when treatment with drops alone is ineffective. It is not generally recommended for prolonged administration. The modified release capsules are considerably more expensive than the tablets. See prescribing points below for cautions.
Acetazolamide injection 500mg is used in emergency situations and in the pre-operative treatment of closed angle glaucoma. See prescribing points below for cautions.
Apraclonidine 0.5% (eye drops, proprietary name Iopidine®) is used as a short-term adjunctive treatment of chronic glaucoma in patients not adequately controlled by another drug.
Bimatoprost (eye drops, proprietary name Lumigan®) is used for adjunctive treatment of chronic glaucoma in patients not adequately controlled by another drug, or as monotherapy in patients intolerant of other therapy. Before initiating treatment, patients should be advised of possible change in eye colour.
Brimonidine 0.2% (eye drops, proprietary name Alphagan®) is used to control open angle glaucoma or ocular hypertension in patients who are intolerant to, or poorly controlled by topical beta-blockers, and as 'add on' therapy.
Brinzolamide/timolol (eye drops, Azarga®) is used to decrease intraocular pressure (IOP) in adult patients with open-angle glaucoma or ocular hypertension for whom monotherapy provides insufficient IOP reduction. Use is restricted to patients who do not tolerate the ocular side-effects of dorzolamide/timolol (Cosopt®).
Dipivefrine 0.1% (eye drops, proprietary name Propine®) is a pro-drug of adrenaline. It is claimed to pass into the cornea where it is then converted to the active form and so may be useful where the local and systemic side-effects of adrenaline are to be avoided.
Dorzolamide 2% (eye drops, proprietary name Trusopt®) is available when topical treatment with a beta-adrenoceptor blocking eye drop is unsuitable, or as adjunctive therapy to beta-adrenoceptor blocking drugs (see below). When used alone it should be applied three times daily. It is associated with allergic reactions, including topical hypersensitivity. Preservative-free drops are available for patients with a proven sensitivity to benzalkonium chloride.
Dorzolamide 2%/timolol 0.5% (eye drops, proprietary name Cosopt®) is available for patients in whom this is an appropriate combination of agents, as a treatment option for the treatment of elevated intra-ocular pressure in patients with open-angle glaucoma and pseudo-exfoliative glaucoma when topical beta-blocker monotherapy is not sufficient. When combined with a beta-blocker it should be applied twice daily. Preservative-free eye drops (UDVs) are available for patients who have a proven sensitivity to the preservative benzalkonium chloride.
Glycerol 15% (eye drops) is a "special" and is occasionally used as a hypertonic agent in acute glaucoma.
Latanoprost (eye drops, proprietary name Xalatan®) is used for the control of ocular hypertension or glaucoma. It is restricted to patients in whom conventional beta-adrenoceptor blocking drugs are contra-indicated or when beta-adrenoceptor blocking drugs alone are not sufficient. Before initiating treatment, patients should be advised of possible change in eye colour. It is applied once daily, preferably in the evening.
Latanoprost/timolol eye drops (eye drops, proprietary name Xalacom®) is available for patients in whom this is an appropriate combination of agents. It decreases pressure in the eye in patients with open-angle glaucoma or ocular hypertension who are insufficiently responsive to topical beta-blockers or prostaglandin analogues alone. It is applied once daily.
Mannitol 10 or 20% given intravenously may be useful as a short-term ocular hypotensive.
Travoprost/timolol (eye drops, proprietary name DuoTrav®) is available for patients in whom this is an appropriate combination of agents. It decreases pressure in the eye in patients with open-angle glaucoma or ocular hypertension who are insufficiently responsive to topical beta-blockers or prostaglandin analogues alone. Available for general use, treatment may be initiated in the community on the recommendation of a consultant/specialist.
- Systemic absorption may follow topical application of eye drops containing beta-adrenoceptor blocking drugs. This route of administration avoids first-pass metabolism in the liver. Hence even the low concentrations used in ocular preparation can exert serious adverse effects. The CSM has therefore advised that these preparations, even those with apparent cardioselectivity, should not be used in patients with asthma or a history of obstructive airways disease, unless no alternative treatment is available. They should also be used with caution in patients who have a history of bradycardia, heart block, or heart failure. Beta-adrenoceptor blocking drugs may reduce exercise tolerance in the elderly and cause depression and other psychotropic manifestations.
- Beta-adrenoceptor blocking eye drops may be used alone or in combination with other drugs such as pilocarpine, dorzolamide, latanoprost or oral acetazolamide.
- Acetazolamide is a sulphonamide derivative and therefore may potentiate folic acid antagonists, hypoglycaemic drugs and oral anticoagulants. It may also cause hypokalaemia, especially if patients have a low potassium diet or are taking potassium-wasting diuretics. It should be avoided in patients with severe renal impairment, and sulphonamide hypersensitivity.