Oral Beta-Adrenergic Receptor Inhibitors
Patients who are receiving a beta-adrenergic receptor inhibiting agents orally and Timolol GFS should be observed for potential additive effects of beta-blockade, both systemic and on intraocular pressure. Patients should not usually receive two topical ophthalmic beta-adrenergic receptor inhibiting agents concurrently.
Digitalis and Calcium Antagonists
The concomitant use of beta-adrenergic receptor inhibiting agents with digitalis and calcium antagonists may have additive effects in prolonging atrioventricular conduction time.
Caution should be used in the coadministration of beta-adrenergic receptor inhibitors, such as Timolol GFS, and oral or intravenous calcium antagonists because of possible atrioventricular conduction disturbances, left ventricular failure, or hypotension. In patients with impaired cardiac function, co-administration should be avoided.
Close observation of the patient is recommended when a beta receptor inhibitor 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.
Potentiated systemic beta-blockade (e.g., decreased heart rate) has been reported during combined treatment with quinidine and timolol, possibly because quinidine inhibits the metabolism of timolol via the P-450 enzyme, CYP2D6.
Oral beta-adrenergic receptor inhibitor 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.
[See Warnings and Precautions (5.11) ]