Beyond SSRI and SNRI antidepressants are two other very interesting medications for depression, Wellbutrin (bupropion) and Remeron (mirtazapine). Wellbutrin is called an NDRI antidepressant (= a Norepinephrine and Dopamine Reuptake Inhibitor). Notice right away is does not have effects on serotonin which confers both an advantage and disadvantage for Wellbutrin. The disadvantage is that without serotonin effects it does not treat anxiety disorders (GAD, Panic Disorder, PTSD, Social Anxiety Disorder and OCD) along with treating major depression. On the other hand it does not have any sexual dysfunction as a side effect, the bane of SSRI antidepressants (Prozac, Paxil, Zoloft, Celexa, Lexapro, Luvox, Viibryd and Trintellix).
Similarly Wellbutrin has no weight gain as an issue. If there are not anxiety issues then Wellbutrin can be a first choice medication for many patients. Furthermore if there is only a partial improvement with an SSRI then Wellbutrin, due to its differing mechanism of action, can be combined with the SSRIs to produce a better antidepressant effect. Finally, if there is preexisting sexual dysfunction as a side effect of the SSRI then Wellbutrin will treat or mitigate sexual dysfunction.