Tricyclic antidepressants (TCAs)

As a class, TCAs are the most effective medications for selective neuropathic pain conditions in humans.⁷⁹ In dogs, there exists only a single case report where amitriptyline was used for neuropathic musculoskeletal pain.⁸⁰

Selective serotonin (norepinephrine) reuptake inhibitors [SS(N)RIs]

These compounds exert their effect by increasing serotonin with or without norepinephrine in the synaptic cleft. At least one SS(N)RI, duloxetine, has a chronic pain label indication in humans. In dogs, bioavailability is poor and clinical efficacy is lacking.⁸¹

At this point in the manuscript, the Task Force wants to emphasize that many drugs and compounds enhance either monoamines or serotonin expression. Caution should be used when such analgesic agents are used in combination. Examples include tramadol, TCAs (including amitriptyline and clomipramine), SS(N)RIs, amantadine, metoclopramide, selegiline, amitraz, mirtazapine, and trazodone.