Timolol

Brand Names: Timoptol

Drug Class: Non-selective beta-adrenergic blocking agent

Overview

Timolol is a non-selective beta-adrenergic blocking agent used primarily in ophthalmic formulations to reduce elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. It works by decreasing aqueous humor production, thereby lowering IOP and reducing the risk of optic nerve damage. When combined with dorzolamide (a carbonic anhydrase inhibitor), it provides enhanced IOP reduction through complementary mechanisms.

Mechanism of Action

Timolol is a non-selective beta-adrenergic receptor antagonist that reduces intraocular pressure by decreasing aqueous humor production in the ciliary body. It blocks both beta-1 and beta-2 adrenergic receptors, leading to reduced cAMP production and subsequent inhibition of aqueous humor secretion.

Indications

  • Reduction of elevated intraocular pressure in patients with open-angle glaucoma
  • Treatment of ocular hypertension

Common Doses

  • 0.25% ophthalmic solution
  • 0.5% ophthalmic solution

Dosage

For ophthalmic use: One drop in the affected eye(s) twice daily. When using multiple topical ophthalmic medications, administer at least 5 minutes apart.

Contraindications

  • Bronchial asthma or history of bronchial asthma
  • Severe chronic obstructive pulmonary disease
  • Sinus bradycardia, second- or third-degree atrioventricular block
  • Overt cardiac failure
  • Cardiogenic shock
  • Hypersensitivity to any component of this product

Side Effects

  • Ocular: Burning, stinging, itching, blurred vision, conjunctival hyperemia
  • Systemic: Bradycardia, hypotension, bronchospasm, headache, dizziness, fatigue
  • Serious: Cardiac arrhythmias, heart failure, severe bronchospasm, depression, hallucinations

Interactions

  • Oral beta-blockers: Additive systemic beta-blockade effects
  • Calcium channel blockers: May potentiate conduction disturbances
  • Digitalis glycosides: May have additive effects on AV conduction
  • Catecholamine-depleting drugs (reserpine): May produce additive effects and hypotension
  • Insulin and oral hypoglycemics: May mask hypoglycemic symptoms

Counseling Points

  • Wash hands before use
  • Do not touch dropper tip to any surface to avoid contamination
  • Wait at least 5 minutes between different eye medications
  • Remove contact lenses before administration and wait 15 minutes before reinserting
  • May cause temporary blurred vision after administration
  • Report any breathing difficulties, slow heartbeat, or dizziness to healthcare provider