Drug Interaction Report

Limited data indicate that thiazide diuretics and/or triamterene may increase the probability of adverse reactions to amantadine. The mechanism is unknown but may be related to reduced clearance of amantadine, resulting in increased plasma levels. Possible reactions include ataxia, confusion, and agitation. If an interaction is suspected, the dosage of amantadine may be reduced or discontinued, or a different diuretic may be substituted.

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.