timolol

Timolol is a non-selective beta-adrenergic blocker used primarily in ophthalmology to treat elevated intraocular pressure associated with open-angle glaucoma and ocular hypertension. It lowers intraocular pressure by decreasing the production of aqueous humor in the ciliary body, an effect mediated through antagonism of beta-adrenergic receptors (beta-1 and beta-2). Timolol is typically formulated as an ophthalmic solution containing timolol maleate.

In clinical use, timolol is most often administered as eye drops, commonly in 0.25% or 0.5% strengths, one or two times daily depending on the formulation and response. It may be prescribed as monotherapy or in fixed-dose combinations with other glaucoma agents, such as dorzolamide (Cosopt) or brimonidine (Combigan). Systemic timolol tablets once served to treat hypertension and angina, but topical ophthalmic timolol is the preferred form for ocular conditions, owing to fewer systemic effects. Systemic exposure from eye drops can occur via nasolacrimal drainage and may cause adverse effects elsewhere in the body.

Common adverse effects of ophthalmic timolol include transient local irritation, stinging, and conjunctival hyperemia. Systemic beta-blockade can lead to bradycardia, hypotension, bronchospasm (particularly in patients with asthma or COPD), and masking of hypoglycemia. Timolol is contraindicated in patients with severe bradycardia, second- or third-degree heart block, overt heart failure, cardiogenic shock, or hypersensitivity to the drug; caution is advised in asthma, COPD, diabetes, and concurrent beta-blocker use.

Brand names include Timolol in various formulations such as Timoptic and Istalol; fixed-dose combinations include Cosopt (with dorzolamide) and Combigan (with brimonidine).