Timolol (0.5% w/v) is a non-selective beta-adrenergic receptor blocking agent (beta-blocker) formulated as an ophthalmic solution. It is a cornerstone therapy in the management of open-angle glaucoma and ocular hypertension in the Indian market, primarily by reducing elevated as well as normal intraocular pressure (IOP). It is a first-line agent due to its potent IOP-lowering efficacy, established safety profile, and cost-effectiveness.
Adult: One drop of 0.5% solution in the affected eye(s) twice daily. In some patients, the IOP may be adequately controlled with one drop once daily (e.g., in the morning).
Note: Wash hands before use. Tilt head back, pull lower eyelid down to form a pouch. Instill one drop. Close eyes gently for 1-2 minutes. Apply gentle pressure with a finger to the lacrimal sac (inner corner of the eye) for at least 1 minute to minimize systemic absorption. Wait at least 5-10 minutes before instilling any other topical ophthalmic medication. Do not touch dropper tip to eye or any surface.
Timolol reduces intraocular pressure (IOP) primarily by decreasing the production of aqueous humor by the ciliary body. It has little to no effect on the outflow facility (conventional uveoscleral outflow). The reduction in aqueous humor formation is mediated through blockade of beta-1 and beta-2 adrenergic receptors in the ciliary processes.
Pregnancy: Pregnancy Category C (US FDA). Animal studies have shown adverse effects. There are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus. Systemic beta-blockers have been associated with fetal bradycardia, hypoglycemia, and intrauterine growth restriction.
Driving: May cause transient blurred vision, dizziness, or fatigue after instillation. Patients should not drive or use machinery until their vision is clear and they are sure they are not affected.
| Other Beta-Blockers (Oral/Systemic) | Additive systemic beta-blockade leading to severe bradycardia, heart block, heart failure. | Major |
| Calcium Channel Blockers (e.g., Verapamil, Diltiazem) | Potentiates negative inotropic and chronotropic effects; risk of hypotension, bradycardia, and heart failure. | Major |
| Digoxin | Additive effects on AV conduction; increased risk of bradycardia. | Moderate |
| Insulin, Oral Hypoglycemics | Timolol may mask tachycardia (a warning sign) of hypoglycemia and may impair glucose recovery. May also cause hypertension. | Moderate |
| Catecholamine-depleting drugs (e.g., Reserpine) | Additive hypotensive and bradycardic effects; may produce vertigo, syncope. | Major |
| Adrenergic Agonists (e.g., Epinephrine for glaucoma) | Initial hypertensive episode followed by bradycardia. Paradoxical decrease in heart rate. | Moderate |
| Quinidine, CYP2D6 Inhibitors | May inhibit timolol metabolism, increasing systemic levels and risk of adverse effects. | Moderate |