Preservative-Freeinteractions

Potential additive effect of oral carbonic anhydrase inhibitor with dorzolamide hydrochloride and timolol maleate ophthalmic solution (preservative free). Potential acid-base and electrolyte disturbances. Concomitant use with systemic beta-blockers may potentiate systemic beta-blockade. Oral or intravenous calcium antagonists may cause atrioventricular conduction disturbances, left ventricular failure, and hypotension. Catecholamine-depleting drugs may have additive effects and produce hypotension and/or marked bradycardia. Digitalis and calcium antagonists may have additive effects in prolonging atrioventricular conduction time. CYP2D6 inhibitors may potentiate systemic beta-blockade.

7.1 Oral Carbonic

Anhydrase Inhibitors There is a potential for an additive effect on the known systemic effects of carbonic anhydrase inhibition in patients receiving an oral carbonic anhydrase inhibitor and dorzolamide hydrochloride and timolol maleate ophthalmic solution (preservative free). The concomitant administration of dorzolamide hydrochloride and timolol maleate ophthalmic solution (preservative free) and oral carbonic anhydrase inhibitors is not recommended.

7.2 High-Dose

Salicylate Therapy Although acid-base and electrolyte disturbances were not reported in the clinical trials with dorzolamide hydrochloride ophthalmic solution, these disturbances have been reported with oral carbonic anhydrase inhibitors and have, in some instances, resulted in drug interactions (e.g., toxicity associated with high-dose salicylate therapy). Therefore, the potential for such drug interactions should be considered in patients receiving dorzolamide hydrochloride and timolol maleate ophthalmic solution (preservative free).

7.3 Beta-Adrenergic

Blocking Agents Patients who are receiving a beta-adrenergic blocking agent orally and dorzolamide hydrochloride and timolol maleate ophthalmic solution (preservative free) should be observed for potential additive effects of beta-blockade, both systemic and on intraocular pressure. The concomitant use of two topical beta-adrenergic blocking agents is not recommended.

7.4 Calcium

Antagonists Caution should be used in the coadministration of beta-adrenergic blocking agents, such as dorzolamide hydrochloride and timolol maleate ophthalmic solution (preservative free), and oral or intravenous calcium antagonists because of possible atrioventricular conduction disturbances, left ventricular failure, and hypotension. In patients with impaired cardiac function, coadministration should be avoided.

7.5 Catecholamine-Depleting

Drugs Close observation of the patient is recommended when a beta-blocker is administered to patients receiving catecholamine-depleting drugs such as reserpine, because of possible additive effects and the production of hypotension and/or marked bradycardia, which may result in vertigo, syncope, or postural hypotension.

7.6 Digitalis and

Calcium Antagonists The concomitant use of beta-adrenergic blocking agents with digitalis and calcium antagonists may have additive effects in prolonging atrioventricular conduction time.

7.7 CYP2D6 Inhibitors

Potentiated systemic beta-blockade (e.g., decreased heart rate, depression) has been reported during combined treatment with CYP2D6 inhibitors (e.g., quinidine, SSRIs) and timolol.

7.8 Clonidine

Oral beta-adrenergic blocking agents may exacerbate the rebound hypertension which can follow the withdrawal of clonidine. There have been no reports of exacerbation of rebound hypertension with ophthalmic timolol maleate.