Drug Interactions between digitoxin and timolol ophthalmic

MONITOR: Concomitant use of digitalis glycosides and beta-blockers may increase the risk of bradycardia. These agents slow atrioventricular conduction and decrease heart rate, hence they may have additive cardiac effects during coadministration. Some beta-blockers such as carvedilol, esmolol, and talinolol have also been reported to increase the systemic bioavailability of digoxin. The mechanism may involve enhanced absorption as well as reduced renal excretion of digoxin due to inhibition of intestinal and renal P-glycoprotein efflux transporter.

MANAGEMENT: Caution is advised during coadministration of digitalis glycosides and beta-blockers. Serum digitalis levels, heart rate, and blood pressure should be monitored closely, particularly during the first few weeks of concomitant therapy. Patients should be advised to notify their physician if they experience anorexia, nausea, visual changes, irregular heartbeat, slow pulse, dizziness, or syncope. Beta-blockers should not be used in patients with overt or decompensated congestive heart failure, as sympathetic stimulation may be a vital component in maintaining hemodynamic function in these patients and its inhibition by beta blockade may worsen the heart failure.