Hypertensive urgency induced by an interaction of mirtazapine and clonidine

Mirtazapine is a new antidepressant with a tetracyclic chemical structure t hat is not related to selective serotonin reuptake inhibitors, tricyclic an tidepressants, or monoamine oxidase inhibitors. The antidepressant effect r esults from stimulation of the noradrenergic system through antagonism at c entral alpha(2)-inhibitory receptors. Clonidine exerts its antihypertensive effect by stimulating these receptors to cause a reduction in endogenous r elease of norepinephrine. Therefore, the two agents have mechanisms of acti on that potentially oppose one another. We report: a case of hypertensive u rgency that ensued after a patient stabilized on clonidine began taking mir tazapine.