Vitaly Gordin

A genetic association study of the functional A118G polymorphism of the human mu-opioid receptor gene in patients with acute and chronic pain.

In this prospective, observational study we explored whether A118G single nucleotide polymorphism in the human &mgr;-opioid receptor (MOR) gene could explain the inter-individual differences in opioid analgesic requirements in patients with acute postoperative pain and chronic pain. The frequency of the wild-type A118 MOR (major) and variant G118 MOR (minor) alleles in the subjects with chronic, noncancer pain (n = 121) and opioid-naïve subjects with acute postoperative pain (n = 101), serving as the control group, were examined. The relationships among the A118G MOR genotype, opioid requirements, and the numerical pain score were analyzed in both groups. The frequency of the minor allele was significantly lower in the subjects with chronic pain when compared with the group with acute postoperative pain (0.079 versus 0.158; P = 0.009 by &khgr;2 test). No statistically significant association was observed between the presence of A118G MOR polymorphism and the average postoperative pain score or the doses of morphine used in the immediate postoperative period. In the high-quartile, opioid utilization, chronic pain patients, the homozygotic carriers of the major allele required significantly higher opioid dose than did the carriers of the minor allele. The results indicate that although the presence of the minor allele does not appear to affect opioid analgesic use in acute postoperative pain, the minor allele is less common in chronic pain patients, especially in those requiring higher doses of opioid analgesics.

Combination therapy for neuropathic pain: a review of current evidence.

Neuropathic pain is a debilitating chronic condition that remains very difficult to treat. Recently, a number of clinical studies have compared the effectiveness of combination drug therapy with monotherapy for neuropathic pain treatment. In this article, we summarize up-to-date clinical studies of combination therapy for the treatment of both cancer- and non-cancer-related neuropathic pain. Despite a relatively small number of clinical studies on this topic, several positive indications have emerged. First, clinical studies using gabapentin (five positive trials) and pregabalin (five positive trials and one negative trial) in combination with an opioid, cyclo-oxygenase-2 inhibitor or antidepressant have shown positive responses greater than the respective monotherapies for pain related to diabetic neuropathy and post-herpetic neuropathy. Second, high-concentration (8%) topical capsaicin and a 5% lidocaine patch seem to be effective add-on therapies (a modality of combination therapy) for various neuropathic pain conditions. Third, combination therapy for cancer-related neuropathic pain has yielded only limited success based on a number of small-scale clinical studies.While there are benefits of using combination therapy for neuropathic pain treatment, including better pain relief and reduced adverse effects, more clinical studies are required in order to (i) make head-to-head comparisons between combination and single-drug therapies, (ii) identify symptom-specific combination therapies for distinctive clinical neuropathic pain conditions, (iii) explore combination therapies that include non-drug modalities such as physical therapy, psychological coping and biofeedback to facilitate functional restoration and (iv) develop new and objective evaluation tools for clinical outcome assessment.

Epidural steroid injections compared with gabapentin for lumbosacral radicular pain: multicenter randomized double blind comparative efficacy study

Objective To evaluate whether an epidural steroid injection or gabapentin is a better treatment for lumbosacral radiculopathy. Design A multicenter randomized study conducted between 2011 and 2014. Computer generated randomization was stratified by site. Patients and evaluating physicians were blinded to treatment outcomes. Settings Eight military, Veterans Administration, and civilian hospitals. Participants 145 people with lumbosacral radicular pain secondary to herniated disc or spinal stenosis for less than four years in duration and in whom leg pain is as severe or more severe than back pain. Interventions Participants received either epidural steroid injection plus placebo pills or sham injection plus gabapentin. Main outcome measures Average leg pain one and three months after the injection on a 0-10 numerical rating scale. A positive outcome was defined as a ≥2 point decrease in leg pain coupled with a positive global perceived effect. All patients had one month follow-up visits; patients whose condition improved remained blinded for their three month visit. Results There were no significant differences for the primary outcome measure at one month (mean pain score 3.3 (SD 2.6) and mean change from baseline −2.2 (SD 2.4) in epidural steroid injection group versus 3.7 (SD 2.6) and −1.7 (SD 2.6) in gabapentin group; adjusted difference 0.4, 95% confidence interval −0.3 to 1.2; P=0.25) and three months (mean pain score 3.4 (SD 2.7) and mean change from baseline −2.0 (SD 2.6) versus 3.7 (SD 2.8) and −1.6 (SD 2.7), respectively; adjusted difference 0.3, −0.5 to 1.2; P=0.43). Among secondary outcomes, one month after treatment those who received epidural steroid injection had greater reductions in worst leg pain (−3.0, SD 2.8) than those treated with gabapentin (−2.0, SD 2.9; P=0.04) and were more likely to experience a positive successful outcome (66% v 46%; number needed to treat=5.0, 95% confidence interval 2.8 to 27.0; P=0.02). At three months, there were no significant differences between treatments. Conclusions Although epidural steroid injection might provide greater benefit than gabapentin for some outcome measures, the differences are modest and are transient for most people. Trial registration ClinicalTrials.gov Identifier: NCT01495923.

Incidence of Neuropathic Pain after Cooled Radiofrequency Ablation of Sacral Lateral Branch Nerves

OBJECTIVE To determine the incidence of neuropathic pain after cooled radiofrequency ablation (RFA) of the sacral lateral branches for the treatment of chronic posterior sacroiliac joint complex pain. DESIGN Retrospective chart review of all patients with chronic posterior sacroiliac joint complex pain who underwent cooled RFA of the sacral lateral branches in our practice between July 2011 and February 2014. SETTING Single academic pain practice at a tertiary care medical center. SUBJECTS Thirty-six patients with chronic posterior sacroiliac joint complex pain. METHODS All charts were reviewed to determine the procedure date, unilateral or bilateral, number of levels treated, and number of individual lesions. Side effects were assessed for their presence or absence, character, intensity, duration, and whether treatment was initiated or symptoms resolved spontaneously. RESULTS Forty-eight separate procedures were performed, with a total of 193 levels and 430 lesions. Three patients had transient postprocedure neuropathic pain yielding a 0.7% (95% confidence interval [CI]± 0.4%) rate of this complication per lesion. This proportion increases to 6.2% (95% CI ± 3.5%) per procedure and to 9.4% (95% CI ± 5.2%) per patient. CONCLUSION The incidence of postprocedural neuropathic pain after cooled RFA for posterior sacroiliac joint complex denervation is low and in a similar range to that in the lumbar spine. We consider this procedure safe to be utilized by pain medicine practitioners.

Serotonin Syndrome in a Patient with Chronic Pain Polypharmacy

Dear Editor: We report a case of serotonin syndrome in a patient taking five agents that have known or reported serotonergic association. Symptoms began a year prior and were missed by multiple clinicians despite the addition of more serotonergic agents. We would like to discuss the importance of medication review, physical examination, and awareness of serotonin syndrome. A 41-year-old 84-kg woman presented to our chronic pain management clinic for removal of a lumbar spinal stimulator. Her past medical history included lumbar spondylosis with radiculopathy, cervical spondylosis with radiculopathy, anxiety, depression, osteoarthritis of the shoulders, and seasonal allergic rhinitis. Her surgical history included the placement of a spinal cord stimulator 3 years prior, multiple lumbar facet joint injections, a lumbar nerve radiofrequency ablation, a cervical epidural steroid injection, and two cesarean sections. Her medication list at the time of presentation was amitriptyline 50 mg daily, carisoprodol 350 mg three times daily, cetirizine 10 mg daily, cyclobenzaprine 5–10 mg at bedtime, duloxetine 120 mg at bedtime, gabapentin 800 mg three times daily, and tramadol 50 mg four times daily. She had been treated by a chronic pain specialist up to 3 years prior to her presentation with us. She received multiple injections and eventually a spinal cord stimulator for her lumbar back pain. She reported taking duloxetine for several years at 60 mg daily. She also reported taking a combination of duloxetine, celecoxib, pregabalin, and over-the-counter analgesics during that time …

Pain management for low back pain

LEARNING OBJECTIVES: After reading this article, the participant should be able to: Describe the indications and therapeutic benefits of epidural steroid, sacroiliac joint, and intrathecal injections for low back pain. Describe the indications and therapeutic benefits of radiofrequency facet nerve rhizotomy and spinal cord stimulation for low back pain. Discuss the most recent literature concerning interventional pain management for treatment of low back pain.

Acute Management of the Opioid-Dependent Patient

Seventy million patients are afflicted by and treated for chronic pain in the United States and treated more frequently with long-term opioids, particularly morphine, oxycodone, and methadone in the treatment of non-cancer pain. Many of these patients will arrive for surgical procedures, and pain management will be a major part of their hospital stay. According to various sources, approximately 40 % of all surgical patients still experience moderate to severe pain and almost a quarter of them experience inadequate pain relief. Allowing patients to suffer from poorly controlled pain not only may be considered a breach of human rights but may result in emotional and cognitive problems, negatively impacting postoperative rehabilitation and quality of life.

The Role of Cytokines in Chronic Pain Processing and Opioid Tolerance: An Australian Study

In this issue of Pain Medicine , an Australian group of researchers studied two cytokines, interleukin (IL)-6 and IL-10, in the patients receiving intrathecal (IT) opioid analgesics via implantable drug delivery system [1]. These cytokines have been shown to play opposite roles in pain processing with IL-6 being a pro-inflammatory and pronociceptive cytokine whereas IL-10 possesses anti-inflammatory and antinociceptive properties. Zin and colleagues compared the plasma and the cerebrospinal fluid (CSF) concentrations of these two cytokines and assessed pain intensity in a group of 50 patients (Group A) receiving long-term (mean 5 years) IT infusion of either morphine or hydromorphone as monotherapy or in combination with a local anesthetic. Additionally, they studied the same parameters in a pilot group of 10 patients (Group B), who were followed for 3 months from the time of the initiation of IT therapy. Cytokines are released in the periphery by a variety of cells such as macrophages, …