Pain, negative affective states and opioid-based analgesics: Safer pain therapies to dampen addiction

Treatment of Moderate-to-Severe Pain in Hepatocellular Carcinoma with Transcutaneous Electrical Acupoint Stimulation: A Randomized Controlled Trial

Objective

Moderate-to-severe pain is the most common clinical symptom in patients with hepatocellular carcinoma (HCC).This trial aimed to analyze the clinical efficacy of Transcutaneous electrical acupoint stimulation (TEAS) in patients of HCC with severe pain and provide a reliable reference for optimizing the clinical diagnostic and therapeutic strategies of HCC.

Methods

A total of 104 eligible patients were randomly allocated to experimental and control groups in a ratio of 1:1.The treatment was administered for 1 week continuously. Patients in both groups were followed up 1 week after the end of the treatment.The primary outcome measure was the Numerical Rating Scale (NRS) score, whereas the secondary outcome measures included Brief Pain Inventory BPI-Q3, Q4, Q5 scores, analgesic dose, frequency of opioid-induced gastrointestinal side effects, Karnofsky Performance Status (KPS), Quality of Life Scale - Liver Cancer (QOL-LC), and Brief Fatigue Inventory (BFI) scores.

Results

The NRS scores of experimental group was significantly lower after treatment and at the follow-up than baseline (average P<0.01), there were also statistical differences between the groups at the above time points (average P<0.01). BPI-Q3, -Q4, and -Q5 scores in the experimental group were decreased after treatment when compared with those before treatment (average P<0.01). Furthermore, there were significant improvements of gastrointestinal side effects, KPS, QOL-LC and BPI in the experimental group after treatment, and the above results were statistically significant compared to the control group.

Conclusion

7-day TEAS treatment can significantly enhance the analgesic effect and maintain for the following week, also reduce the incidence of gastrointestinal side effects caused by opioids, and improve the quality of life of patients with moderate-to-severe HCC-related pain, which has reliable safety and certain clinical promotion value.

Endogenous opioid systems alterations in pain and opioid use disorder

Decades of research advances have established a central role for endogenous opioid systems in regulating reward processing, mood, motivation, learning and memory, gastrointestinal function, and pain relief. Endogenous opioid systems are present ubiquitously throughout the central and peripheral nervous system. They are composed of four families, namely the μ (MOPR), κ (KOPR), δ (DOPR), and nociceptin/orphanin FQ (NOPR) opioid receptors systems. These receptors signal through the action of their endogenous opioid peptides β-endorphins, dynorphins, enkephalins, and nociceptins, respectfully, to maintain homeostasis under normal physiological states. Due to their prominent role in pain regulation, exogenous opioids-primarily targeting the MOPR, have been historically used in medicine as analgesics, but their ability to produce euphoric effects also present high risks for abuse. The ability of pain and opioid use to perturb endogenous opioid system function, particularly within the central nervous system, may increase the likelihood of developing opioid use disorder (OUD). Today, the opioid crisis represents a major social, economic, and public health concern. In this review, we summarize the current state of the literature on the function, expression, pharmacology, and regulation of endogenous opioid systems in pain. Additionally, we discuss the adaptations in the endogenous opioid systems upon use of exogenous opioids which contribute to the development of OUD. Finally, we describe the intricate relationship between pain, endogenous opioid systems, and the proclivity for opioid misuse, as well as potential advances in generating safer and more efficient pain therapies.