Category Archives: Chronic Inflammatory and Neuropathic Pain

Role of endocannabinoid system in dopamine signalling within the reward circuits affected by chronic pain.

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Pharmacological Research

“The association between chronic pain, depression and anxiety has gained particular attention due to high rates of comorbidity. Recent data demonstrated that the mesolimbic reward circuitry is involved in the pathology of chronic pain. Interestingly, the mesolimbic reward circuit participates both in pain perception and in pain relief.

The endocannabinoid system (ECS) has emerged as a highly relevant player involved in both pain perception and reward processing. Targeting ECS could become a novel treatment strategy for chronic pain patients.

However, little is known about the underlying mechanisms of action of cannabinoids at the intersection of neurochemical changes in reward circuits and chronic pain. Because understanding the benefits and risks of cannabinoids is paramount, the aim of this review is to evaluate the state-of-art knowledge about the involvement of the ECS in dopamine signalling within the reward circuits affected by chronic pain.”

https://www.ncbi.nlm.nih.gov/pubmed/30831242

https://www.sciencedirect.com/science/article/abs/pii/S1043661819300088?via%3Dihub

Cannabinoids: a new approach for pain control?

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“To analyze available data related to the use of cannabinoids in medicine, with a special focus on pain management in cancer. The use of cannabis for medical purposes is growing but there are still numerous questions to be solved: effectiveness, safety, and specific indications.

RECENT FINDINGS:

There is considerable variation between countries in the approaches taken, reflecting a variety of historical and cultural factors and despite few randomized controlled studies using natural cannabinoids, there is a trend to state that the use of cannabis should be taken seriously as a potential treatment of cancer-related pain. Cannabidiol, a nontoxic phytocannabinoid with few side-effects is promising in various indications in medicine.

SUMMARY:

The endocannabinoid system is a potential therapeutic target. Cannabinoids may be considered as potential adjuvant in cancer-related pain management. Cannabidiol appears to be the drug of choice. Analgesic trial designs should evolve to get closer to real-life practice and to avoid biases.”

https://www.ncbi.nlm.nih.gov/pubmed/30789867

https://insights.ovid.com/crossref?an=00001622-900000000-00002

An Update of Current Cannabis-Based Pharmaceuticals in Pain Medicine.

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“Cannabis users have long reported therapeutic properties of the plant for a variety of conditions, some of which include nausea, emesis, seizures, cancer, neurogenic diseases and pain control. Research has elucidated many cannabinoid pharmacodynamic and pharmacokinetic properties, expanding the potential use of cannabinoids as a medical therapy.

Due to the inconsistent delivery and control of the active components involved with smoking, pharmaceutical companies are investigating and prioritizing routes other than smoke inhalation for therapeutic use of cannabinoids. In this relatively new field of pharmaceutical development, ongoing drug development promises great benefit from targeted endocannabinoid receptor agonism.

Available in Canada and Europe, nabiximols, a specific extract from the Cannabis plant, has demonstrated great benefit in the treatment of pain related to spasticity in multiple sclerosis, cancer and otherwise chronic pain conditions.

The cannabidiol oral solution Epidiolex®, which is available in the USA, is indicated for management of refractory epilepsy but may offer therapeutic relief to chronic pain conditions as well.

Current investigative drugs, such as those developed by Cara Therapeutics and Zynerba Pharmaceuticals, are synthetic cannabinoids which show promise to specifically target neuropsychiatric conditions and chronic pain symptoms such as neuropathy and allodynia.

The objective of this review is to provide clinicians with an update of currently available and promising developmental cannabis pharmaceutical derivatives which may stand to greatly benefit patients with otherwise difficult-to-treat chronic conditions.”

https://www.ncbi.nlm.nih.gov/pubmed/30721403

https://link.springer.com/article/10.1007%2Fs40122-019-0114-4

A Cost-Effectiveness Model for Adjunctive Smoked Cannabis in the Treatment of Chronic Neuropathic Pain

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“A recent meta-analysis affirmed the benefit of medicinal cannabis for chronic neuropathic pain, a disabling and difficult-to-treat condition. As medicinal cannabis use is becoming increasingly prevalent among Americans, an exploration of its economic feasibility is warranted. We present this cost-effectiveness analysis of adjunctive cannabis pharmacotherapy for chronic peripheral neuropathy.

A growing body of scientific literature demonstrates reproducible efficacy of cannabis in the treatment of several medical conditions, including chronic neuropathic pain. Clinical trials of oral, smoked, and vaporized cannabis and cannabinoids have all demonstrated analgesic benefit of medicinal cannabis in the treatment of this costly and disabling condition. A recent meta-analysis of individual patient data from five randomized controlled trials of inhaled cannabis demonstrated pain relief comparable to gabapentin. Treatment guidelines for neuropathic pain recommend consideration of cannabinoids as third-line agents.

As recently proposed willingness-to-pay thresholds for the United States health marketplace range from $110,000 to $300,000 per QALY, cannabis appears cost-effective when augmenting second-line treatment for painful neuropathy. Further research is warranted to explore the long-term benefit of smoked cannabis and standardization of its dosing for chronic neuropathic pain.”

https://www.ncbi.nlm.nih.gov/pubmed/30944870

https://www.liebertpub.com/doi/10.1089/can.2018.0027

“New study analyzes cost effectiveness of smoked cannabis to treat chronic neuropathic pain” https://www.eurekalert.org/pub_releases/2019-01/mali-nsa012919.php

Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol.

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 ACS Chemical Neuroscience

“Cannabis (Cannabis sativa) is the most widely used illicit drug in the world, with an estimated 192 million users globally.

The main psychoactive component of cannabis is (-)-trans-Δ9-tetrahydrocannabinol (Δ9-THC), a molecule with a diverse range of pharmacological actions. The unique and distinctive intoxication caused by Δ9-THC primarily reflects partial agonist action at central cannabinoid type 1 (CB1) receptors.

Δ9-THC is an approved therapeutic treatment for a range of conditions, including chronic pain, chemotherapy-induced nausea and vomiting, and is being investigated in indications such as anorexia nervosa, agitation in dementia, and Tourette’s syndrome.

It is available as a regulated pharmaceutical in products such as Marinol®, Sativex®, and Namisol®, as well as in an ever-increasing range of unregistered medicinal and recreational cannabis products.

While cannabis is an ancient medicament, contemporary use is embroiled in legal, scientific, and social controversy, much of which relates to the potential hazards and benefits of Δ9-THC itself.

Robust contemporary debate surrounds the therapeutic value of Δ9-THC in different diseases, its capacity to produce psychosis and cognitive impairment, and the addictive and “gateway” potential of the drug.

This review will provide a profile of the chemistry, pharmacology, toxicology, and recreational and therapeutic uses of Δ9-THC, as well as the historical and societal importance of this unique, distinctive, and ubiquitous psychoactive substance.”

https://www.ncbi.nlm.nih.gov/pubmed/30689342

https://pubs.acs.org/doi/10.1021/acschemneuro.8b00651

Perspectives on cannabis as a substitute for opioid analgesics.

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 Future Medicine Logo“With the opioid epidemic reaching new heights in the USA, it has become critical to find suitable alternatives to opioids.

Cannabis, an antinociceptive, is a strong contender to help patients reduce their opioid usage.

A growing literature has been examining the complex effects cannabis has on pain relief and on opioid usage; whether it is a substitute for opioids or increases their use. This review explores the studies that compare cannabis-opioid interactions and presents some challenges of cannabis research and usage.

The practical clinical pharmacology of cannabis as an analgesic, including the route of administration, safety and pharmacokinetics, are discussed to address the concerns, as well as possible solutions, of cannabis as a pain reliever.”

https://www.ncbi.nlm.nih.gov/pubmed/30681029

https://www.futuremedicine.com/doi/10.2217/pmt-2018-0051

Some Prospective Alternatives for Treating Pain: The Endocannabinoid System and Its Putative Receptors GPR18 and GPR55.

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Image result for frontiers in pharmacology“Marijuana extracts (cannabinoids) have been used for several millennia for pain treatment.

Regarding the site of action, cannabinoids are highly promiscuous molecules, but only two cannabinoid receptors (CB1 and CB2) have been deeply studied and classified.

Thus, therapeutic actions, side effects and pharmacological targets for cannabinoids have been explained based on the pharmacology of cannabinoid CB1/CB2 receptors. However, the accumulation of confusing and sometimes contradictory results suggests the existence of other cannabinoid receptors.

Different orphan proteins (e.g., GPR18, GPR55, GPR119, etc.) have been proposed as putative cannabinoid receptors.

According to their expression, GPR18 and GPR55 could be involved in sensory transmission and pain integration.

This work summarized novel data supporting that, besides cannabinoid CB1 and CB2receptors, GPR18 and GPR55 may be useful for pain treatment.

Conclusion: There is evidence to support an antinociceptive role for GPR18 and GPR55.”

https://www.ncbi.nlm.nih.gov/pubmed/30670965

https://www.frontiersin.org/articles/10.3389/fphar.2018.01496/full

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

The Anti-Inflammatory Properties of Terpenoids from Cannabis.

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“Cannabinoids are well known to have anti-inflammatory effects in mammalians; however, the Cannabis plant also contains other compounds such as terpenoids, whose biological effects have not yet been characterized. The aim of this study was to compare the anti-inflammatory properties of terpenoids with those of cannabidiol (CBD).

Materials and Methods: Essential oils prepared from three monoecious nonpsychoactive chemotypes of Cannabis were analyzed for their terpenoid content and subsequently studied pharmacologically for their anti-inflammatory properties in vitro and in vivo.

Results: In vitro, the three essential oils rich in terpenoids partly inhibited reactive oxygen intermediate and nitric oxide radical (NO•) production in RAW 264.7 stimulated macrophages. The three terpenoid-rich oils exerted moderate anti-inflammatory activities in an in vivo anti-inflammatory model without affecting tumor necrosis factor alpha (TNFα) serum levels.

Conclusions: The different Cannabis chemotypes showed distinct compositions of terpenoids. The terpenoid-rich essential oils exert anti-inflammatory and antinociceptive activities in vitro and in vivo, which vary according to their composition. Their effects seem to act independent of TNFα. None of the essential oils was as effective as purified CBD. In contrast to CBD that exerts prolonged immunosuppression and might be used in chronic inflammation, the terpenoids showed only a transient immunosuppression and might thus be used to relieve acute inflammation.”

https://www.ncbi.nlm.nih.gov/pubmed/30596146

https://www.liebertpub.com/doi/10.1089/can.2018.0014

Cannabinoids and Pain: New Insights From Old Molecules.

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Image result for frontiers in pharmacology “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
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