Pain
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The counterirritation phenomenon known as conditioned pain modulation, or diffuse noxious inhibitory control in animals, is of increasing interest due to its utility in predicting chronic pain and treatment response. It features considerable interindividual variability, with large subsets of pain patients and even normal volunteers exhibiting hyperalgesia rather than hypoalgesia during or immediately after receiving a conditioning stimulus. ⋯ In a series of parametric studies, we show that this hyperalgesia can be reliably observed using multiple conditioning stimuli (acetic acid and orofacial formalin), test stimuli (hindpaw and forepaw-withdrawal, tail-withdrawal, hot-plate, and von Frey tests) and genotypes (CD-1, DBA/2, and C57BL/6 mice and Sprague-Dawley rats). Although the magnitude of the hyperalgesia is dependent on the intensity of the conditioning stimulus, we find that the direction of effect is dependent on the effective test stimulus intensity, with lower-intensity stimuli leading to hyperalgesia and higher-intensity stimuli leading to hypoalgesia.
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Review Meta Analysis
The prevalence and the burden of pain in patients with Huntington disease: a systematic review and meta-analysis.
It is remarkable that studies focusing on the prevalence and the burden of pain in patients with Huntington disease (HD) are scarce. This may lead to inadequate recognition of pain and hence lack of treatment, eventually affecting the quality of life. The aim of this review is to investigate the prevalence of pain and its burden in HD by performing a systematic literature search. ⋯ The results demonstrate that pain could be an important nonmotor symptom in patients with HD, and there are indications that the pain burden could be diminished because of HD. Larger and high-quality prospective cohort and clinical studies are required to confirm these findings. In the meantime, awareness about pain and its burden in patients with HD is warranted in clinical practice.
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Randomized Controlled Trial Multicenter Study
A multicenter randomized controlled trial on the efficacy of intradiscal methylene blue injection for chronic discogenic low back pain: the IMBI study.
A study published in PAIN in 2010 showed remarkable effects of intradiscal methylene blue (MB) injections compared with placebo on pain intensity in patients with chronic discogenic low back pain (CD-LBP). Both groups received lidocaine hydrochloride injections for pain associated with the procedure. We replicated the design of the previously published study and performed a multicenter, double-blind, randomized, placebo-controlled trial to assess whether the extraordinary effects of MB on pain intensity could be confirmed. ⋯ We were unable to confirm that intradiscal MB injections are better capable of significantly reducing pain in patients with CD-LBP 6 months after treatment compared with placebo. We observed that over one-quarter of patients receiving only lidocaine injections reported treatment success, which is in contrast with the previously published study. Our results do not support the recommendation of using intradiscal MB injections for patients with CD-LBP.
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Randomized Controlled Trial
An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia.
In this experimental randomized placebo-controlled 4-way crossover trial, we explored the analgesic effects of inhaled pharmaceutical-grade cannabis in 20 chronic pain patients with fibromyalgia. We tested 4 different cannabis varieties with exact knowledge on their [INCREMENT]-tetrahydrocannabinol (THC) and cannabidiol (CBD) content: Bedrocan (22.4-mg THC, <1-mg CBD; Bedrocan International BV, Veendam, the Netherlands), Bediol (13.4-mg THC, 17.8-mg CBD; Bedrocan International BV, Veendam, the Netherlands), Bedrolite (18.4-mg CBD, <1-mg THC; Bedrocan International BV, Veendam, the Netherlands), and a placebo variety without any THC or CBD. After a single vapor inhalation, THC and CBD plasma concentrations, pressure and electrical pain thresholds, spontaneous pain scores, and drug high were measured for 3 hours. ⋯ Cannabidiol inhalation increased THC plasma concentrations but diminished THC-induced analgesic effects, indicative of synergistic pharmacokinetic but antagonistic pharmacodynamic interactions of THC and CBD. This experimental trial shows the complex behavior of inhaled cannabinoids in chronic pain patients with just small analgesic responses after a single inhalation. Further studies are needed to determine long-term treatment effects on spontaneous pain scores, THC-CBD interactions, and the role of psychotropic symptoms on pain relief.