Human heat sensation: A randomized crossover trial.

Sensing of noxious heat has been reported to be mediated by TRPV1, TRPA1, TRPM3, and ANO1 in mice, and this is redundant so that the loss of one receptor is at least partially compensated for by others. We have established an infusion-based human heat pain model. Heat-induced pain probed with antagonists for the four receptors did not match the redundancy found in mice. In healthy participants, only TRPV1 contributes to the detection of noxious heat; none of the other three receptors are involved. TRPV1 inhibition reduced the pain at all noxious temperatures, which can also be seen as an increase in the temperature that causes a particular level of pain. However, even if the TRPV1-dependent shift in heat detection is about 1°C, at the end of the temperature ramp to 52°C, most heat-induced pain remains unexplained. This difference between species reopens the quest for the molecular safety net for the detection of noxious heat in humans.

Oral cannabidiol (CBD) as add-on to paracetamol for painful chronic osteoarthritis of the knee: a randomized, double-blind, placebo-controlled clinical trial.

Background: Painful knee osteoarthritis (KOA) is common, pharmacological treatment, however, is often hampered by limited tolerability. Cannabidiol, which preclinically showed anti-inflammatory, analgesic activity, could supplement established analgesics, but robust clinical trials are lacking. The aim of our study was to investigate the effects of oral high-dose CBD administered over 8 weeks on pain, function and patient global assessment as an add-on to continued paracetamol in chronic symptomatic KOA. Methods: Prospective, randomized, placebo-controlled, double-blind, parallel-group study. Single center, Outpatient Clinic, Department of Special Anaesthesia and Pain Therapy at Medical University of Vienna, Austria. Eligibility criteria included: age: 18-98 years; painful KOA; score ≥5 on the pain subscale of the Western Ontario and McMasters Universities Osteoarthritis (WOMAC) Index; KOA confirmed by imaging. Participants were on continued dosage of paracetamol 3 g/d and randomly assigned by web-based software 1:1 to oral cannabidiol 600 mg/d (n = 43) or placebo (n = 43). Study period: 8 weeks. Primary outcome: Change in WOMAC pain subscale scores (0 = no pain, 10 = worst possible pain) from baseline to week 8 of treatment. Trial Registration: ClinicalTrials.gov Identifier: NCT04607603. Trial is completed. Findings: The trial was conducted from October 1, 2020 to March 29, 2022. 159 patients screened, 86 randomized. Among 86 participants (mean age, 62.8 [SD 20.3] years; 60 females [69.8%]), 58 (67.4%) completed the trial. Mean baseline WOMAC pain subscale was 6.0 ± 1.1. Analysis: Intention-to-treat principal. Mean reduction in WOMAC pain subscale was 2.5 (95% CI: 1.8-3.3) in the cannabidiol group and 2.4 (95% CI: 1.7-3.2) in the placebo group with no significant group difference (p = 0.80). Adverse events were significantly more frequent with cannabidiol (cannabidiol: 135 [56%]; placebo: 105 [44%]) (p = 0.008). Rise above baseline of liver aminotransferases and gamma-glutamyltransferase was significantly more common in the cannabidiol (n = 15) than the placebo group (n = 5) (p = 0.02). Interpretation: In KOA patients, oral high-dose add-on cannabidiol had no additional analgesic effect compared to adding placebo to continued paracetamol. Our results do not support the use of cannabidiol as an analgesic supplement in KOA. Funding: Trigal Pharma GmbH.

Effect of Regular Electrotherapy on Spinal Flexibility and Pain Sensitivity in Patients with Chronic Non-Specific Neck Pain and Low Back Pain: A Randomized Controlled Double-Blinded Pilot Trial.

Background and Objectives: Chronic neck pain and low back pain are common conditions in high-income countries leading to social and medical problems such as invalidity and decreased quality of life. The aim of this study was to investigate the effect of supra-threshold electrotherapy on pain level, subjective feeling of disability, and spinal mobility in patients with chronic pain in the spinal cord. Materials and Methods: 11 men and 24 women with a mean age of 49 years were randomly divided into three groups: group 1, "therapy": supra-threshold electrotherapy was applied on the whole back after electrical calibration; group 2, "control": electrical calibration without successive electrotherapy; group 3, "control of control": no stimulation. Sessions were performed once a week and six times in total, each lasting 30 min. The numeric pain rating scale (NRS), cervical and lumbar range of motion (ROM), as well as disability in daily live were investigated before and after the sessions using questionnaires (Neck Disability Index, Roland Morris Questionnaire, Short-form Mc Gill Pain Questionnaire (SF-MPQ)). Results: Spinal mobility improved significantly in the lumbar anteflexion (baseline mean, 20.34 ± SD 1.46; post session mean, 21.43 ± SD 1.95; p = 0.003) and retroflexion (baseline mean, 13.68 ± SD 1.46; post session mean, 12.05 ± SD 1.37; p = 0.006) in the group receiving electrotherapy. Pain levels measured by the NRS and disability-questionnaire scores did not differ significantly before and after treatment in any of the groups. Conclusions: Our data indicate that regular supra-threshold electrotherapy for six times has a positive effect on lumbar flexibility in chronic neck pain and low back pain patients, whereas pain sensation or subjective feeling of disability remained unchanged.

[Clinical efficacy of auricular vagus nerve stimulation in the treatment of chronic and acute pain : A systematic review]. / Klinische Wirksamkeit der aurikulären Vagusnervstimulation in der Behandlung chronischer und akuter Schmerzen : Eine systematische Übersichtsarbeit.

BACKGROUND: Current guidelines recommend a personalized, multimodal, and interdisciplinary approach for the treatment of chronic pain. Already in the acute treatment of postoperative pain, it can be useful to minimize risk factors for chronification. Auricular vagus nerve stimulation (aVNS) could be an effective non-drug therapy for the treatment of chronic and acute pain. AIM OF THE WORK: The aim of this systematic review is to evaluate the clinical efficacy of aVNS in chronic and acute pain as well as its effect on medication intake. MATERIALS AND METHODS: A systematic literature search was carried out on the application of auricular electrical stimulation in chronic and acute pain. Studies were classified according to their level of evidence and evaluated via the Jadad scale as well as their scientific validity, and then analyzed in terms of indication, method, stimulation parameters, duration of treatment, efficacy, and safety. RESULTS: Twenty studies on chronic pain indications, ten studies on acute postoperative pain, as well as seven studies on experimental acute pain were identified and analyzed. The search revealed a total of n = 1105 aVNS-treated patients. The best evidence on the efficacy of aVNS is available for the indications chronic low back pain, chronic cervical syndrome, chronic abdominal pain, and chronic migraine as well as acute postoperative pain in oocyte aspiration, laparoscopic nephrectomy, and open colorectal surgery. Additionally a significant reduction in analgesic or opiate intake was evident in most studies. In three randomized controlled trials in chronic pain patients, a sustainable pain reduction over a period of up to 12 months was shown. Overall, aVNS was very well tolerated. CONCLUSION: This review indicates that aVNS can be a complementary and effective non-drug treatment for patients with chronic and acute postoperative pain. Future studies in these indications should focus on standardizing and optimizing treatment parameters, inclusion of quality-of-life outcome parameters, and longer follow-up periods to better understand the sustainable therapeutic effect of aVNS.