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Acute poisoning from atypical (non-SSRI) antidepressants, including serotonin-norepinephrine reuptake inhibitors (SNRI)

Author
Alicia B Minns, MD
Section Editor
Stephen J Traub, MD
Deputy Editor
Jonathan Grayzel, MD, FAAEM

INTRODUCTION

The dual-action serotonin-norepinephrine reuptake inhibitors (SNRI) and other atypical antidepressants were introduced over the last two decades and are used to treat of a variety of conditions, such as depression, anxiety, and smoking cessation. Atypical antidepressants are those that do not clearly fit the standard classifications for antidepressants (discussed below). Most are derivatives of selective serotonin reuptake inhibitors (SSRIs).

While generally safer in overdose than tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs), SNRIs may exhibit greater toxicity than SSRIs [1]. Commonly used atypical antidepressants include venlafaxine (Effexor), desvenlafaxine (Pristiq), duloxetine (Cymbalta), milnacipran (Savella), mirtazapine (Remeron), and bupropion (Wellbutrin, Zyban), and vilazodone (Viibryd).

The clinical manifestations, diagnosis, and management of acute poisoning from SNRIs and other common atypical antidepressants are reviewed here. The therapeutic use of these medications, management of poisoning from SSRIs, the diagnosis and management of serotonin syndrome, and other related issues are discussed separately. (See "Serotonin-norepinephrine reuptake inhibitors (SNRIs): Pharmacology, administration, and side effects" and "Selective serotonin reuptake inhibitor poisoning" and "Serotonin syndrome (serotonin toxicity)" and "General approach to drug poisoning in adults" and "Approach to the child with occult toxic exposure".)

PHARMACOLOGY AND CELLULAR TOXICOLOGY

Atypical antidepressants are those that do not clearly fit the standard classifications for antidepressants. They are not monoamine oxidase inhibitors (MAOI), cyclic antidepressants (CA), or selective serotonin reuptake inhibitors (SSRIs). However, most share structural similarities with SSRIs. Although atypical antidepressants manifest fewer side effects than MAOIs and CAs, a few drugs in this class are more toxic than SSRIs in overdose.

Serotonin is produced by the metabolism of L-tryptophan. It exerts its action by binding to 5-hydroxytryptophan (5-HT) receptors, of which there are seven types that are further divided into multiple subtypes. In the central nervous system (CNS), serotonergic neurons are primarily located in the brainstem and assist in the regulation of sleep, affective behavior, food intake, temperature regulation, migraines, emesis, sexual behavior, nociception, and motor tone. In the peripheral nervous system, serotonin plays a role in the regulation of vascular tone and gastrointestinal motility. Although most adverse effects of SNRIs are a direct extension of the pharmacologic effects of serotonin, certain agents have unique toxicities, as outlined below [2].

                                 

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Literature review current through: Aug 2017. | This topic last updated: Aug 17, 2017.
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