[Long-term treatment of chronic pain with low-dose 7-day buprenorphine transdermal patch. Observational data from elderly patients of pain relief and quality of life]

Neuropeptide and cytokine regulation of pain in the context of substance use disorders

Substance use disorders (SUDs) are frequently accompanied by affective symptoms that promote negative reinforcement mechanisms contributing to SUD maintenance or progression. Despite their widespread use as analgesics, chronic or excessive exposure to alcohol, opioids, and nicotine produces heightened nociceptive sensitivity, termed hyperalgesia. This review focuses on the contributions of neuropeptide (CRF, melanocortin, opioid peptide) and cytokine (IL-1β, TNF-α, chemokine) systems in the development and maintenance of substance-induced hyperalgesia. Few effective therapies exist for either chronic pain or SUD, and the common interaction of these disease states likely complicates their effective treatment. Here we highlight promising new discoveries as well as identify gaps in research that could lead to more effective and even simultaneous treatment of SUDs and co-morbid hyperalgesia symptoms.

Pain Control in Latin America: The Optimized Role of Buprenorphine in the Treatment of Cancer and Noncancer Pain

Pain is a terrible health problem that transcends borders and nationalities, although there may be significant differences among regions regarding pain management. In Latin America (LatAm, composed of the many nations of Central America, South America, Mexico, and the Caribbean), access to healthcare, pain management, and opioid analgesics can vary. Despite an international U.S.-led trend toward greater control in opioid prescribing, the role of opioids in the management of severe pain in LatAm is probably smaller than it should be, as opioid consumption in LatAm overall is low. Buprenorphine is a strong opioidwith certain characteristics that make it a potentially useful analgesic agent in LatAm: it has a unique pharmacology that allows for transdermal administration and a favorable safety profile with a ceiling effect for respiratory depression. It has a well-studied low risk potential for misuse, and there is strong evidence for its safety and efficacy in managing both cancer and noncancer pain in adults. Caregivers and policy makers in LatAm may learn from the U.S. experience with opioids in order to develop protocols to better and safely manage pain, and it is possible that buprenorphine will play a key role.

Kappa Opioid Receptors Drive a Tonic Aversive Component of Chronic Pain

Pain is a multidimensional experience and negative affect, or how much the pain is "bothersome", significantly impacts the sufferers' quality of life. It is well established that the κ opioid system contributes to depressive and dysphoric states, but whether this system contributes to the negative affect precipitated by the occurrence of chronic pain remains tenuous. Using a model of persistent pain, we show by quantitative real-time-PCR, florescence in situ hybridization, Western blotting and GTPgS autoradiography an upregulation of expression and the function of κ opioid receptors (KORs) and its endogenous ligand dynorphin in the mesolimbic circuitry in animals with chronic pain compared with surgical controls. Using in vivo microdialysis and microinjection of drugs into the mesolimbic dopamine system, we demonstrate that inhibiting KORs reinstates evoked dopamine release and reward-related behaviors in chronic pain animals. Chronic pain enhanced KOR agonist-induced place aversion in a sex-dependent manner. Using various place preference paradigms, we show that activation of KORs drives pain aversive states in male but not female mice. However, KOR antagonist treatment was effective in alleviating anxiogenic and depressive affective-like behaviors in both sexes. Finally, ablation of KORs from dopamine neurons using AAV-TH-cre in KOR^loxP mice prevented pain-induced aversive states as measured by place aversion assays. Our results strongly support the use of KOR antagonists as therapeutic adjuvants to alleviate the emotional, tonic-aversive component of chronic pain, which is argued to be the most significant component of the pain experience that impacts patients' quality of life.SIGNIFICANCE STATEMENT We show that KORs are sufficient to drive the tonic-aversive component of chronic pain; the emotional component of pain that is argued to significantly impact a patient's quality of life. The impact of our study is broadly relevant to affective disorders associated with disruption of reward circuitry and thus likely contributes to many of the devastating sequelae of chronic pain, including the poor response to treatment of many patients, debilitating affective disorders (other disorders including anxiety and depression that demonstrate high comorbidity with chronic pain) and substance abuse. Indeed, coexisting psychopathology increases pain intensity, pain-related disability and effectiveness of treatments (Jamison and Edwards, 2013).