Drug Interaction Report

MONITOR: The concomitant use of tocainide and beta-blockers may have additive effects on cardiac index, left ventricular function, and pulmonary wedge pressure. While significant interactions have not been reported in studies, cases of asystole have been reported in patients with preexisting electrophysiologic abnormalities after tocainide and metoprolol were coadministered. The mechanism is not known, but may be related to an additive effect on the sinus node or conduction system, especially in patients with sick sinus syndrome. Cases of confusion and paranoia have also been reported after coadministration of tocainide and propranolol.

MANAGEMENT: The concomitant use of tocainide and beta blockers should probably be avoided in patients with atrioventricular conduction abnormalities or sick sinus syndrome. This combination should be used cautiously in other patients, with careful dose titration and close clinical and electrocardiographic monitoring for efficacy and safety.

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.