Syndrome of neurotoxicity induced by opioid in oncology patients in palliative care

Abstract

Opioid-induced neurotoxicity (NIO) is a neuropsychiatric syndrome of neuronal hyper excitability associated with opioid toxicity. The aim of this review is to determine the evidence over the past ten years about the pathophysiology, diagnosis, prevention and treatment of this entity, in order to generate clear recommendations about it. We conducted a thorough review of the available literature on different databases, only 28 articles met the inclusion criteria. The results showed that the pathophysiology of NIO relates to inhibition of cholinergic and dopaminergic system at CNS, accumulation of toxic metabolites of the opioids and the loss of endogenous pain regulation. The most common symptoms are described in the NIO: delirium, hallucinations, myoclonus, hyperalgesia, allodynia and seizures. The treatment is aimed at correcting the possible triggers, evaluate the dosage and indications of opioid use before they are initiated and finally the most important recommendation is to rotate to another opioid as a measure to improve the symptoms of NIO. In conclusion the NIO is a common secondary effect to opioid use, underdiagnosed, which generates a neurological dysfunction can severely impact the quality of life of patients and family, hindering a proper pain treatment. It is preventable, easily diagnosed and its treatment is to identify triggers, hydration and opioid rotation.