Mirtazapine in Veterinary Medicine a Pharmacological Rationale for its Application in Chronic Pain

Problem statement: Many recent studies have shown that antidepressant agents have analgesic effects in addition to their intended primary actions. The Tricyclic Antidepressants (TCAs) have been recognized as an effective first-line treatment of human neuropathic pain but unfortunately they display a wide range of side effects. Recent studies have shown that Selective Serotonin Reuptake Inhibitors (SSRI) also have potential analgesic effects, albeit of a lower potency compared with the TCAs. Despite this, there is a trend for their increased use, in place of TCAs, in the treatment of chronic pain. Mirtazapine, a SSRI has been recently investigated in the context of veterinary medicine. It has shown favourable pharmacokinetic profiles. Despite the fact that it has mainly been used for anorexia and as an antiemetic for veterinary patients thus far, it could be potentially useful for the treatment of a wide range of anxiety-related conditions and as an analgesic in chronic and cancer-associated pain, due to its effects on both the noradrenergic and serotonic system. Rationale for the use of mirtazapine in veterinary medicine is reviewed in light of previously published literature. Conclusion/Recommendations: Mirtazapine is proposed as a potential analgesic for use in a multidrug analgesic regime in the context of veterinary medicine. Further studies need to be performed before it is implemented in clinical practice however.