Mirtazapine Clonidine

The authors recognized that mirtazapine alone could have caused the hypertensive event. In postmarketing surveillance of mirtazapine, hypertension occurred in at least 1% of patients. However, it is likely that the patient lost antihypertensive control because mirtazapine antagonized the antihypertensive effect of clonidine. Mirtazapine, a tetracyclic antidepressant, stimulates the noradrenergic system through antagonism at central alpha2 inhibitory receptors, which is precisely opposite to the effect of clonidine. 

This interaction is the same as the one when clonidine is combined with TCAs however, mirtazapine is a more potent a2-receptor blocker than the TCAs avoid this interaction and choose an alternative antidepressant without a2-blocking effects. 

Hypertension has been reported with mirtazapine plus clonidine (6). 

Abo-Zena RA, Bobek MB, Dweik RA. Hypertensive urgency induced by an interaction of mirtazapine and clonidine. Pharmacotherapy 2000 20(4) 476-8. 

The tricyclic antidepressants, clomipramine, desipramine and imipramine, reduce or abolish the antihypertensive effects of clonidine. Other tricyclics are expected to behave similarly. A hypertensive crisis developed in a woman taking clonidine who was also given imipramine, and severe pain ocenrred in a man taking amitriptyline and diamorphine when he was given intrathecal clonidine. Conversely, the tetracyclics, maprotiline and mianserin do not appear to alter the antihypertensive effects of clonidine. An isolated case report describes a hypertensive crisis in a patient taking mirtazapine and clonidine. Hypotension ocenrred in a boy taking clonidine and trazodone. 

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