Some tricyclic antidepressants (TCAs) are NRIs by mechanism. While other TCAs are anxiety-reducing, these are drive-enhancing. Since TCAs are non-selective, their stimulating effects are tempered by antihistaminic effects. These noradrenergic TCAs could be co-prescribed with a monoamine oxidase inhibitor (MAOI) without causing serotonin syndrome, but expect the pharmacist to flip out. Taking serotonergic TCAs (amitriptyline, imipramine, clomipramine) with an MAOI could be catastrophic.