timolol maleate: clinical use

Prescribing considerations

• Confirm formulation and indication: oral and ophthalmic products have substantially different systemic exposure and licensing.
• Review respiratory and cardiovascular history; ophthalmic administration does not eliminate systemic beta blockade.
• Use caution in diabetes, spontaneous hypoglycaemia, peripheral vascular disease, first-degree heart block, corneal disease, psoriasis and hyperthyroidism.
• Inform the anaesthetist before surgery because beta blockade can alter cardiovascular responses and the response to adrenaline.
• Avoid abrupt withdrawal, particularly in ischaemic heart disease.

Contraindications and cautions

• Selected products contraindicate use in asthma or a history of asthma, severe obstructive pulmonary disease, clinically important bradycardia or conduction block, overt cardiac failure and cardiogenic shock.
• The selected oral product additionally contraindicates pregnancy, hypotension, severe peripheral circulatory disease, metabolic acidosis, untreated phaeochromocytoma, Prinzmetal’s angina and monoamine oxidase inhibitor treatment.
• The selected eye gel additionally contraindicates corneal dystrophies and untreated phaeochromocytoma.

Monitoring

• For ocular treatment, monitor intraocular pressure, the corneal surface and treatment response.
• Monitor pulse, blood pressure and symptoms of cardiac failure or bronchospasm where systemic effects are a concern.
• Consider closer glucose monitoring in people treated for diabetes because hypoglycaemia may be intensified or masked.
• Observe more closely when combined with other beta blockers, rate-limiting cardiac medicines or antiarrhythmics.

Clinical pharmacology

Timolol is a competitive, non-selective beta-adrenoceptor antagonist. Ocular administration reduces aqueous humour production and intraocular pressure; oral administration reduces heart rate, contractility and myocardial oxygen demand. Ophthalmic absorption through the nasolacrimal pathway can produce systemic beta blockade.

Formulation and product differences

• Tablets provide systemic treatment for cardiovascular indications and migraine prevention.
• The selected multidose eye solution is preserved with benzalkonium chloride, which can affect soft lenses and the ocular surface.
• The selected single-dose eye gel is preservative-free, must be discarded after opening and should be applied after other eye preparations.
• Contact-lens instructions differ: soft lenses may be reinserted after the waiting period specified for the preserved solution, while lenses should be avoided with the selected gel.

Eye drops

Route: Ophthalmic

Strengths: 2.5 mg/mL, 5 mg/mL, 0.25%, 0.25% w/v, 0.5%, 0.5% w/v