Category Archives: Neuropathic Pain

Cannabinoids-induced peripheral analgesia depends on activation of BK channels.

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 Brain Research“The endogenous cannabinoid system is involved in the physiological inhibitory control of pain and is of particular interest for the development of therapeutic approaches for pain management.

Selective activation of the peripheral CB1 cannabinoid receptor has been shown to suppress the heightened firing of primary afferents, which is the peripheral mechanism underlying neuropathic pain after nerve injury. However, the mechanism underlying this effect of CB1 receptor remains unclear.

The large-conductance calcium-activated potassium (BK) channels have been reported to participate in anticonvulsant and vasorelaxant effects of cannabinoids. We asked whether BK channels participate in cannabinoids-induced analgesia and firing-suppressing effects in primary afferents after nerve injury.

Here, using mice with chronic constriction injury(CCI)-induced neuropathic pain, antinociception action and firing-suppressing effect of HU210 were measured before and after BK channel blocker application. We found that local peripheral application of HU210 alleviated CCI-induced pain behavior and suppressed the heightened firing of injured fibers. Co-administration of IBTX with HU210 significantly reversed the analgesia and the firing-suppressing effect of HU210.

This result indicated that the peripheral analgesic effects of cannabinoids depends on activation of BK channels.”

https://www.ncbi.nlm.nih.gov/pubmed/30615887

https://www.sciencedirect.com/science/article/pii/S0006899319300071?via%3Dihub

Cannabinoids and Pain: New Insights From Old Molecules.

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“Cannabis has been used for medicinal purposes for thousands of years.

The prohibition of cannabis in the middle of the 20th century has arrested cannabis research.

In recent years there is a growing debate about the use of cannabis for medical purposes.

The term ‘medical cannabis’ refers to physician-recommended use of the cannabis plant and its components, called cannabinoids, to treat disease or improve symptoms.

Chronic pain is the most commonly cited reason for using medical cannabis.

Cannabinoids act via cannabinoid receptors, but they also affect the activities of many other receptors, ion channels and enzymes.

Preclinical studies in animals using both pharmacological and genetic approaches have increased our understanding of the mechanisms of cannabinoid-induced analgesia and provided therapeutical strategies for treating pain in humans.

The mechanisms of the analgesic effect of cannabinoids include inhibition of the release of neurotransmitters and neuropeptides from presynaptic nerve endings, modulation of postsynaptic neuron excitability, activation of descending inhibitory pain pathways, and reduction of neural inflammation.

Recent meta-analyses of clinical trials that have examined the use of medical cannabis in chronic pain present a moderate amount of evidence that cannabis/cannabinoids exhibit analgesic activity, especially in neuropathic pain.

The main limitations of these studies are short treatment duration, small numbers of patients, heterogeneous patient populations, examination of different cannabinoids, different doses, the use of different efficacy endpoints, as well as modest observable effects.

Adverse effects in the short-term medical use of cannabis are generally mild to moderate, well tolerated and transient. However, there are scant data regarding the long-term safety of medical cannabis use.

Larger well-designed studies of longer duration are mandatory to determine the long-term efficacy and long-term safety of cannabis/cannabinoids and to provide definitive answers to physicians and patients regarding the risk and benefits of its use in the treatment of pain.

In conclusion, the evidence from current research supports the use of medical cannabis in the treatment of chronic pain in adults. Careful follow-up and monitoring of patients using cannabis/cannabinoids are mandatory.”

https://www.ncbi.nlm.nih.gov/pubmed/30542280

https://www.frontiersin.org/articles/10.3389/fphar.2018.01259/full

Cannabidiol modulates serotonergic transmission and reverses both allodynia and anxiety-like behavior in a model of neuropathic pain

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“Clinical studies indicate that cannabidiol (CBD), the primary nonaddictive component of cannabis that interacts with the serotonin (5-HT)1A receptor, may possess analgesic and anxiolytic effects.

Overall, repeated treatment with low-dose CBD induces analgesia predominantly through TRPV1 activation, reduces anxiety through 5-HT1A receptor activation, and rescues impaired 5-HT neurotransmission under neuropathic pain conditions.”

https://www.ncbi.nlm.nih.gov/pubmed/30157131

https://insights.ovid.com/crossref?an=00006396-900000000-98870

THC and gabapentin interactions in a mouse neuropathic pain model.

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Neuropharmacology

“Clinical studies have shown that the major psychoactive ingredient of Cannabis sativa Δ9-tetrahydrocannabinol (THC) has some analgesic efficacy in neuropathic pain states.

However, THC has a significant side effect profile. We examined whether the profile of THC could be improved by co-administering it with the first-line neuropathic pain medication gabapentin.

These findings indicate that gabapentin synergistically enhances the anti-allodynic actions of THC and improves its therapeutic window.

Thus, THC may represent a potential adjuvant for neuropathic pain medications such as gabapentin.”

https://www.ncbi.nlm.nih.gov/pubmed/30312630

https://www.sciencedirect.com/science/article/pii/S0028390818307779?via%3Dihub

Association of Cannabinoid Administration With Experimental Pain in Healthy Adults A Systematic Review and Meta-analysis

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“Patients have reliably endorsed the belief that cannabis is helpful in alleviating pain.

Cannabinoids (the collective term for all of the drugs examined in this study, including plant-based cannabis, which can contain multiple compounds) have long been considered effective for reducing pain and are frequently proposed as treatment options in pain management.

Cannabinoid drugs may prevent the onset of pain by producing small increases in pain thresholds but may not reduce the intensity of experimental pain already being experienced; instead, cannabinoids may make experimental pain feel less unpleasant and more tolerable, suggesting an influence on affective processes.

Cannabis-induced improvements in pain-related negative affect may underlie the widely held belief that cannabis relieves pain.”

 https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2701671

“Cannabinoid drugs make pain feel ‘less unpleasant, more tolerable'”  https://www.sciencedaily.com/releases/2018/09/180919111454.htm

“Medical marijuana increases pain threshold for patients”  https://www.upi.com/Health_News/2018/09/19/Medical-marijuana-increases-pain-threshold-for-patients/1771537292969/?rc_fifo=1

“Study reveals cannabinoid drugs make pain feel ‘less unpleasant, more tolerable'”  https://medicalxpress.com/news/2018-09-reveals-cannabinoid-drugs-pain-unpleasant.html

“Cannabinoid drugs reduce perceived unpleasantness of painful stimuli and increase tolerance” https://www.news-medical.net/news/20180919/Cannabinoid-drugs-reduce-perceived-unpleasantness-of-painful-stimuli-and-increase-tolerance.aspx

“Cannabinoids appear to increase pain tolerability”  https://www.healio.com/psychiatry/practice-management/news/online/%7B7626bb3f-ce35-4968-99bc-50ecdaac79b7%7D/cannabinoids-appear-to-increase-pain-tolerability

Cannabis analgesia in chronic neuropathic pain is associated with altered brain connectivity.

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“To characterize the functional brain changes involved in δ-9-tetrahydrocannabinol (THC) modulation of chronic neuropathic pain.

RESULTS:

THC significantly reduced patients’ pain compared to placebo. THC-induced analgesia was correlated with a reduction in functional connectivity between the anterior cingulate cortex (ACC) and the sensorimotor cortex. Moreover, the degree of reduction was predictive of the response to THC. Graph theory analyses of local measures demonstrated reduction in network connectivity in areas involved in pain processing, and specifically in the dorsolateral prefrontal cortex (DLPFC), which were correlated with individual pain reduction.

CONCLUSION:

These results suggest that the ACC and DLPFC, 2 major cognitive-emotional modulation areas, and their connections to somatosensory areas, are functionally involved in the analgesic effect of THC in chronic pain. This effect may therefore be mediated through induction of functional disconnection between regulatory high-order affective regions and the sensorimotor cortex. Moreover, baseline functional connectivity between these brain areas may serve as a predictor for the extent of pain relief induced by THC.”

https://www.ncbi.nlm.nih.gov/pubmed/30185448

http://n.neurology.org/content/early/2018/09/05/WNL.0000000000006293

Cannabidiol modulates serotonergic transmission and prevents allodynia and anxiety-like behavior in a model of neuropathic pain.

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“Clinical studies indicate that cannabidiol (CBD), the primary non-addictive component of cannabis that interacts with the serotonin (5-HT) 1A receptor, may possess analgesic and anxiolytic effects. However, its effects on 5-HT neuronal activity, as well as its impact in models of neuropathic pain are unknown.

Seven days of treatment with CBD reduced mechanical allodynia, decreased anxiety-like behavior, and normalized 5-HT activity. Anti-allodynic effects of CBD were fully prevented by capsazepine (10 mg/kg/day, s.c., for 7 days) and partially prevented by WAY 100635 (2 mg/kg/day, s.c., for 7 days), while the anxiolytic effect was blocked only by WAY.

Overall, repeated treatment with low-dose CBD induces analgesia predominantly via TRPV1 activation, reduces anxiety via 5-HT1A receptor activation, and rescues impaired 5-HT neurotransmission under neuropathic pain conditions.”

https://www.ncbi.nlm.nih.gov/pubmed/30157131

https://insights.ovid.com/crossref?an=00006396-900000000-98870

“Cannabis pain relief without the ‘high’. Canadian researchers pinpoint the mechanism of cannabidiol for safe pain relief without side effects”  https://eurekalert.org/pub_releases/2018-10/muhc-cpr102418.php

“Effective dose of cannabidiol for safe pain relief without the typical ‘high'”  https://www.news-medical.net/news/20181025/Effective-dose-of-cannabidiol-for-safe-pain-relief-without-the-typical-high.aspx

Targeting the Endocannabinoid System for Prevention or Treatment of Chemotherapy-Induced Neuropathic Pain: Studies in Animal Models.

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“There is a scarcity of drugs to either prevent or properly manage chemotherapy-induced neuropathic pain (CINP). Cannabis or cannabinoids have been reported to improve pain measures in patients with neuropathic pain.

For this review, a search was done in PubMed for papers that examined the expression of and/or evaluated the use of cannabinoids or drugs that prevent or treat established CINP in a CB receptor-dependent manner in animal models.

Studies suggest there is a specific deficiency of endocannabinoids in the periphery during CINP.

Inhibitors of FAAH and MGL, enzymes that degrade the endocannabinoids, CB receptor agonists, desipramine, and coadministered indomethacin plus minocycline were found to either prevent the development and/or attenuate established CINP in a CB receptor-dependent manner.

The studies analysed suggest that targeting the endocannabinoid system for prevention and treatment of CINP is a plausible therapeutic option. Almost 90% of the studies on animal models of CINP analysed utilised male rodents. Taking into consideration clinical and experimental findings that show gender differences in the mechanisms involved in pain including CINP and in response to analgesics, it is imperative that future studies on CINP utilise more female models.”

https://www.ncbi.nlm.nih.gov/pubmed/30147813
“Cannabis or cannabinoids have been reported to improve pain measures in patients with neuropathic or cancer pain. The studies analysed suggest that targeting the endocannabinoid system for prevention and treatment of CINP is a plausible therapeutic option.” https://www.hindawi.com/journals/prm/2018/5234943/

Personal experience and attitudes of pain medicine specialists in Israel regarding the medical use of cannabis for chronic pain.

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“The scientific study of the role of cannabis in pain medicine still lags far behind the growing use driven by public approval. Accumulated clinical experience is therefore an important source of knowledge. However, no study to date has targeted physicians who actually use cannabis in their daily practice.

RESULTS:

Sixty-four percent of all practicing pain specialists in Israel responded. Almost all prescribe cannabis. Among them, 63% find cannabis moderately to highly effective, 56% have encountered mild or no side effects, and only 5% perceive it as significantly harmful. Common indications are neuropathic pain (65%), oncological pain (50%), arthralgias (25%), and any intractable pain (29%). Leading contraindications are schizophrenia (76%), pregnancy/breastfeeding (65%), and age <18 years (59%). Only 12% rated cannabis as more hazardous than opiates. On a personal note, 45% prefer cannabis for themselves or a family member. Lastly, 54% would like to see cannabis legalized in Israel.

CONCLUSION:

In this survey, pain clinicians experienced in prescribing cannabis over prolonged periods view it as an effective and relatively safe treatment for chronic pain, based on their own experience. Their responses suggest a possible change of paradigm from using cannabis as the last resort.”

 https://www.ncbi.nlm.nih.gov/pubmed/30104896
https://www.dovepress.com/personal-experience-and-attitudes-of-pain-medicine-specialists-in-isra-peer-reviewed-article-JPR

Synthetic peripherally-restricted cannabinoid suppresses chemotherapy-induced peripheral neuropathy pain symptoms by CB1 receptor activation.

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 Neuropharmacology

“Chemotherapy-induced peripheral neuropathy (CIPN) is a severe and dose-limiting side effect of cancer treatment that affects millions of cancer survivors throughout the world and current treatment options are extremely limited by their side effects.

Cannabinoids are highly effective in suppressing pain symptoms of chemotherapy-induced and other peripheral neuropathies but their widespread use is limited by central nervous system (CNS)-mediated side effects.

Here, we tested one compound from a series of recently developed synthetic peripherally restricted cannabinoids (PRCBs) in a rat model of cisplatin-induced peripheral neuropathy.

Our results demonstrate that PRCBs exemplified by PrNMI may represent a viable option for the treatment of CIPN pain symptoms.”

https://www.ncbi.nlm.nih.gov/pubmed/29981335

https://www.sciencedirect.com/science/article/pii/S0028390818303575?via%3Dihub