A fixed-dose combination ophthalmic solution containing a topical carbonic anhydrase inhibitor (Dorzolamide) and a non-selective beta-adrenergic receptor blocker (Timolol). It is a first-line therapy for the reduction of elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension who require more than a single agent. The combination provides additive IOP-lowering efficacy through complementary mechanisms, often with improved patient compliance compared to separate instillations.
Adult: One drop in the affected eye(s) twice daily, approximately 12 hours apart.
Note: 1. Wash hands. 2. Tilt head back. 3. Gently pull lower eyelid to form a pouch. 4. Instill one drop. 5. Close eye gently and apply pressure with a finger at the inner corner of the eye (nasolacrimal occlusion) for 1-2 minutes to minimize systemic absorption. 6. Do not blink excessively or rinse the eye. 7. Wait at least 5 minutes before administering any other ophthalmic medication. 8. Contact lens wearers must remove lenses before use and wait 15 minutes before reinsertion.
This combination reduces intraocular pressure (IOP) through two distinct, complementary mechanisms. Dorzolamide inhibits carbonic anhydrase II in the ciliary processes of the eye, decreasing the formation of bicarbonate ions. This reduces sodium and fluid transport, leading to a decrease in aqueous humor secretion. Timolol is a non-selective beta-adrenergic antagonist that blocks beta-1 and beta-2 receptors in the ciliary body, reducing the production of aqueous humor. The combined effect is an additive reduction in aqueous humor inflow.
Pregnancy: Category C. Dorzolamide: Animal studies showed teratogenicity. Timolol: Associated with fetal bradycardia, hypoglycemia, and respiratory depression. Use only if the potential benefit justifies the potential risk to the fetus. Monitor neonates for beta-blocker effects if used near delivery.
Driving: May cause transient blurred vision, dizziness, or fatigue after instillation. Patients should not drive or use machines until their vision is clear.
| Oral Beta-Blockers (e.g., Propranolol, Metoprolol) | Additive systemic beta-blockade; increased risk of bradycardia, hypotension, heart block, and heart failure. | Major |
| Calcium Channel Blockers (e.g., Verapamil, Diltiazem) | Potentiates negative inotropic and chronotropic effects; risk of severe bradycardia and heart block. | Major |
| Digoxin | Additive effects on AV conduction; increased risk of bradycardia. | Moderate |
| Insulin, Oral Hypoglycemics | Timolol may mask tachycardia (a sign of hypoglycemia) and potentially prolong hypoglycemia. | Moderate |
| Catecholamine-depleting drugs (e.g., Reserpine) | Additive hypotensive and bradycardic effects; may produce vertigo or syncope. | Moderate |
| Quinidine | Potentiates beta-blocker effects. | Moderate |
| Systemic Carbonic Anhydrase Inhibitors (e.g., Acetazolamide) | Additive risk of metabolic acidosis and electrolyte disturbances. | Moderate |
| Clonidine | Potential for rebound hypertension if clonidine is withdrawn while on timolol. | Moderate |
Same composition (Dorzolamide (2% w/v) + Timolol (0.5% w/v)), different brands: