Drug Interactions between Alphagan P and mirtazapine

MONITOR: Tricyclic and tetracyclic antidepressants can diminish the effects of centrally acting alpha agonists. The clinical significance, if any, of this interaction with respect to topically administered alpha-2 adrenergic receptor agonists such as brimonidine is unknown. The possibility of an additive or potentiating central nervous system (CNS)-depressant effect should be considered. Additive hypotensive effects and orthostasis may also occur, particularly during initial dosing of these agents.

MANAGEMENT: Patients receiving topical alpha-2 adrenergic receptor agonists in combination with tricyclic and tetracyclic antidepressants should be made aware of the potential for increased adverse effects such as drowsiness, dizziness, lightheadedness, confusion, hypotension and syncope, and counseled to avoid activities requiring mental alertness until they know how these agents affect them. Patients should also avoid rising abruptly from a sitting or recumbent position and notify their physician if they experience orthostasis or tachycardia. No data are available on the level of circulating catecholamines after withdrawal of a topical alpha-2 adrenergic receptor agonist. Since tricyclic antidepressants can affect the metabolism and uptake of circulating amines, caution is advised.