Antinociception mechanisms of action of cannabinoid-based medicine: an overview for anesthesiologists and pain physicians

 Pain Rounds“Cannabinoid-based medications possess unique multimodal analgesic mechanisms of action, modulating diverse pain targets.

Cannabinoids are classified based on their origin into three categories: endocannabinoids (present endogenously in human tissues), phytocannabinoids (plant derived) and synthetic cannabinoids (pharmaceutical). Cannabinoids exert an analgesic effect, peculiarly in hyperalgesia, neuropathic pain and inflammatory states.

Endocannabinoids are released on demand from postsynaptic terminals and travels retrograde to stimulate cannabinoids receptors on presynaptic terminals, inhibiting the release of excitatory neurotransmitters. Cannabinoids (endogenous and phytocannabinoids) produce analgesia by interacting with cannabinoids receptors type 1 and 2 (CB1 and CB2), as well as putative non-CB1/CB2 receptors; G protein-coupled receptor 55, and transient receptor potential vanilloid type-1. Moreover, they modulate multiple peripheral, spinal and supraspinal nociception pathways.

Cannabinoids-opioids cross-modulation and synergy contribute significantly to tolerance and antinociceptive effects of cannabinoids. This narrative review evaluates cannabinoids’ diverse mechanisms of action as it pertains to nociception modulation relevant to the practice of anesthesiologists and pain medicine physicians.”

https://pubmed.ncbi.nlm.nih.gov/33239391/

https://rapm.bmj.com/content/early/2020/11/24/rapm-2020-102114

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Medical Cannabis Treatment for Chronic Pain: Outcomes and Prediction of Response

Although studied in a few randomized controlled trials (RCTs), the efficacy of medical cannabis (MC) for chronic pain remains controversial. Using an alternative approach, this multicenter, questionnaire-based prospective cohort was aimed to assess the long-term effects of MC on chronic pain of various etiologies and to identify predictors for MC treatment success.

Results: 1045 patients completed the baseline questionnaires and initiated MC treatment, and 551 completed the 12 month follow-up. At one year, average pain intensity declined from baseline by 20% [-1.97 points (95%CI= -2.13 to -1.81; p<0.001)]. All other parameters improved by 10-30% (p<0.001). A significant decrease of 42% [reduction of 27mg; (95%CI= -34.89 to -18.56, p<0.001)] from baseline in morphine equivalent daily dosage of opioids was also observed. Reported adverse effects were common but mostly non-serious. Presence of normal to long sleep duration, lower body mass index (BMI) and lower depression score predicted relatively higher treatment success, whereas presence of neuropathic pain predicted the opposite.

Conclusions: This prospective study provides further evidence for the effects of MC on chronic pain and related symptoms, demonstrating an overall mild to modest long-term improvement of the tested measures and identifying possible predictors for treatment success.

Significance: This “real world” paper shows that MC mildly to modestly attenuates chronic pain and related symptoms. MC treatment can also cause frequent, but mostly non-serious adverse effects, although central nervous system (CNS)-related AEs that can impair the ability to drive vehicles are not uncommon. This study is novel in identifying possible predictors for treatment success, including normal to long sleep duration, lower BMI and lower depression scores. In contrast to current beliefs the diagnosis of neuropathic pain predicts a less favorable outcome. These findings provide physicians with new data to support decision making on recommendations for MC treatment.”

https://pubmed.ncbi.nlm.nih.gov/33065768/

https://onlinelibrary.wiley.com/doi/10.1002/ejp.1675

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Cannabinoid Receptors and Their Relationship With Chronic Pain: A Narrative Review

CB1-versus-CB2-receptors “The burden of chronic pain has affected many individuals leading to distress and discomfort, alongside numerous side effects with conventional therapeutic approaches.

Cannabinoid receptors are naturally found in the human body and have long been an interest in antinociception. These include CB1 and CB2 receptors, which are promising candidates for the treatment of chronic inflammatory pain.

The mechanism of action of the receptors and how they approach pain control in inflammatory conditions show that it can be an adjunctive approach towards controlling these symptoms. Numerous studies have shown how the targeted approach towards these receptors has activated them promoting a release in cytokines, all leading to anti-inflammatory effects and immune system regulation.

Cannabinoid activation of glycine and gamma-aminobutyric acid (GABA) models also showed efficacy in pain management. Chronic conditions such as osteoarthritis were shown to also benefit from this considerable treatment. However, it is unclear how the cannabinoid system works in relation with the pain pathway. Therefore, in this review we aim to analyse the role of the cannabinoid system in chronic inflammatory pain.”

https://pubmed.ncbi.nlm.nih.gov/33072446/

https://www.cureus.com/articles/39887-cannabinoid-receptors-and-their-relationship-with-chronic-pain-a-narrative-review

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The CB2 Agonist β-Caryophyllene in Male and Female Rats Exposed to a Model of Persistent Inflammatory Pain

frontiers – Page 2 – Retraction Watch “Cannabinoids help in pain treatment through their action on CB1 and CB2 receptors.

β-caryophyllene (BCP), an ancient remedy to treat pain, is a sesquiterpene found in large amounts in the essential oils of various spice and food plants such as oregano, cinnamon, and black pepper. It binds to the CB2 receptor, acting as a full agonist.

Sex differences in the BCP-induced analgesic effect were studied by exposing male and female rats to a persistent/repeated painful stimulation.

In conclusion, long-term intake of BCP appears to be able to decrease pain behaviors in a model of repeated inflammatory pain in both sexes, but to a greater degree in males.”

https://pubmed.ncbi.nlm.nih.gov/33013287/

https://www.frontiersin.org/articles/10.3389/fnins.2020.00850/full

“β-caryophyllene (BCP) is a common constitute of the essential oils of numerous spice, food plants and major component in Cannabis.”   http://www.ncbi.nlm.nih.gov/pubmed/23138934

“Beta-caryophyllene is a dietary cannabinoid.”   https://www.ncbi.nlm.nih.gov/pubmed/18574142

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No Evidence of Altered Reactivity to Experimentally Induced Pain Among Regular Cannabis Users

Clinical Journal of Pain,Philadelphia - Gainbuzz“Recent years have seen an increase in the adoption of cannabinoid medicines, which have demonstrated effectiveness for the treatment of chronic pain.

However, the extent to which frequent cannabis use (CU) influences sensitivity to acute pain has not been systematically examined. Such a determination is clinically relevant in light of hypersensitivity to pain associated with prolonged use of other analgesics such as opioids, and reports of increased pain sensitivity to experimentally induced pain during acute cannabis intoxication.

This study explored differences in measures of pain intensity and tolerance. The authors hypothesized that individuals who report frequent CU would demonstrate greater experimental pain sensitivity.

Results: Frequent CU was not associated with hyperalgesia as cannabis users and nonusers did not exhibit differences on measures of pain tolerance (t (78)=-0.05; P=0.96), sensitivity (t (78)=-0.83; P=0.41), or intensity (t (78)=0.36; P=0.72).

Discussion: Frequent cannabis users did not demonstrate hyperalgesia. This finding should help to inform evaluations of the relative harms and benefits of cannabis analgesic therapies.”

https://pubmed.ncbi.nlm.nih.gov/32433075/

https://journals.lww.com/clinicalpain/Abstract/2020/08000/No_Evidence_of_Altered_Reactivity_to.4.aspx

“Pain tolerance among cannabis users. Unlike opioids, long-term cannabis use does not increase sensitivity to pain. “This study should come as good news to patients who are already using cannabis to treat pain,” says co-author Zach Walsh, who leads the UBC Therapeutic Recreational and Problematic Substance Use Lab which hosted the study. “Increases in pain sensitivity with opioids can really complicate an already tough situation; given increasing uptake of cannabis-based pain medications it’s a relief that we didn’t identify a similar pattern with cannabinoids.”

https://www.sciencedaily.com/releases/2020/09/200910120105.htm

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Insights on cannabidiol’s antiallodynic and anxiolytic mechanisms of action in a model of neuropathic pain

PAIN Impact Factor Increase to 6.029 - IASP“Recent studies have shown that cannabidiol (CBD) could have a great therapeutic potential for treating disorders such as chronic pain and anxiety. In the target article, the authors propose that CBD modulates serotonergic transmission and reverses allodynia and anxiety-like behaviour in a rat model of neuropathic pain. Furthermore, this study shows an antinociceptive effect mediated by TRPV1 and partially by 5-HT1A receptors, as well as an anxiolytic effect mediated by 5-HT1A receptors.”

https://pubmed.ncbi.nlm.nih.gov/32766463/

https://journals.lww.com/painrpts/Fulltext/2019/10000/Insights_on_cannabidiol_s_antiallodynic_and.10.aspx

“Cannabidiol modulates serotonergic transmission and reverses both allodynia and anxiety-like behavior in a model of neuropathic pain”  https://pubmed.ncbi.nlm.nih.gov/30157131/

 

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Medical cannabis for chronic pain: can it make a difference in pain management?

SpringerLink “Globally, chronic pain is a major therapeutic challenge and affects more than 15% of the population. As patients with painful terminal diseases may face unbearable pain, there is a need for more potent analgesics.

Although opioid-based therapeutic agents received attention to manage severe pain, their adverse drug effects and mortality rate associated with opioids overdose are the major concerns. Evidences from clinical trials showed therapeutic benefits of cannabis, especially delta-9-tetrahydrocannabinol and cannabinoids reduced neuropathic pain intensity in various conditions. Also, there are reports on using combination cannabinoid therapies for chronic pain management.

The association of cannabis dependence and addiction has been discussed much and the reports mentioned that it can be comparatively lower than other substances such as nicotine and alcohol. More countries have decided to legalise the medicinal use of cannabis and marijuana. Healthcare professionals should keep themselves updated with the changing state of medical cannabis and its applications.

The pharmacokinetics and safety of medical cannabis need to be studied by conducting clinical research. The complex and variable chemically active contents of herbal cannabis and methodological limitations in the administration of cannabis to study participants, make the clinical research difficult.”

https://pubmed.ncbi.nlm.nih.gov/31535218/

https://link.springer.com/article/10.1007%2Fs00540-019-02680-y

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Protective role of neuronal and lymphoid cannabinoid CB 2 receptors in neuropathic pain

 eLife logo“Cannabinoid CB2 receptor (CB2) agonists are potential analgesics void of psychotropic effects.

Peripheral immune cells, neurons and glia express CB2, however the involvement of CB2 from these cells in neuropathic pain remains unresolved. We explored spontaneous neuropathic pain through on-demand self-administration of the selective CB2 agonist JWH133 in wild-type and knockout mice lacking CB2 in neurons, monocytes or constitutively. Operant self-administration reflected drug-taking to alleviate spontaneous pain, nociceptive and affective manifestations. While constitutive deletion of CB2 disrupted JWH133-taking behavior, this behavior was not modified in monocyte-specific CB2 knockouts and was increased in mice defective in neuronal CB2 knockouts suggestive of increased spontaneous pain. Interestingly, CB2-positive lymphocytes infiltrated the injured nerve and possible CB2transfer from immune cells to neurons was found. Lymphocyte CB2depletion also exacerbated JWH133 self-administration and inhibited antinociception.

This work identifies a simultaneous activity of neuronal and lymphoid CB2that protects against spontaneous and evoked neuropathic pain.”

https://pubmed.ncbi.nlm.nih.gov/32687056/

https://elifesciences.org/articles/55582

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The pharmacokinetics, efficacy, and safety of a novel selective‐dose cannabis inhaler in patients with chronic pain: A randomized, double‐blinded, placebo‐controlled trial

European Journal of Pain“Precise cannabis treatment dosing remains a major challenge, leading to physicians’ reluctance to prescribe medical cannabis.

Objective

To test the pharmacokinetics, analgesic effect, cognitive performance and safety effects of an innovative medical device that enables the delivery of inhaled therapeutic doses of Δ9‐Tetrahydrocannabinol (THC) in patients with chronic pain.

Methods

In a randomized, three‐arms, double‐blinded, placebo‐controlled, cross‐over trial, 27 patients received a single inhalation of Δ9‐THC: 0.5mg, 1mg, or a placebo.

Δ9‐THC plasma levels were measured at baseline and up to 150‐min post‐inhalation. Pain intensity and safety parameters were recorded on a 10‐cm visual analogue scale (VAS) at pre‐defined time points. The cognitive performance was evaluated using the selective sub‐tests of the Cambridge Neuropsychological Test Automated Battery (CANTAB).

Results

Following inhalation of 0.5 mg or 1mg, Δ9‐THC plasma max ± SD were 14.3 ± 7.7 and 33.8 ± 25.7 ng/ml. max ± SD were 3.7 ± 1.4 and 4.4 ± 2.1 min, and AUC0 → infinity±SD were 300 ± 144 and 769 ± 331 ng*min/ml, respectively. Both doses, but not the placebo, demonstrated a significant reduction in pain intensity compared with baseline and remained stable for 150‐min. The 1‐mg dose showed a significant pain decrease compared to the placebo. Adverse events were mostly mild and resolved spontaneously. There was no evidence of consistent impairments in cognitive performance.

Conclusion

This feasibility trial demonstrated that a metered‐dose cannabis inhaler delivered precise and low THC doses, produced a dose‐dependent and safe analgesic effect in patients with neuropathic pain/ complex‐regional pain syndrome (CRPS). Thus, it enables individualization of medical cannabis regimens that can be evaluated pharmacokinetically and pharmacodynamically by accepted pharmaceutical models.

Significance

Evidence suggests that cannabis‐based medicines are an effective treatment for chronic pain in adults. The pharmacokinetics of THC varies as a function of its route of administration. Pulmonary assimilation of inhaled THC causes rapid onset of analgesia. However, currently used routes of cannabinoids delivery provide unknown doses, making it impossible to implement a pharmaceutical standard treatment plan. A novel selective‐dose cannabis inhaler delivers significantly low and precise doses of THC, thus allowing the administration of inhaled cannabis‐based medicines according to high pharmaceutical standards. These low doses of THC can produce safe and effective analgesia in patients with chronic pain.

To the best of our knowledge, it is the first time that the delivery of selective, significantly low, and precise therapeutic single doses of inhaled THC demonstrates an analgesic effect. It allows patients to reach the optimum balance between symptom relief and controlled side effects, enabling patients to regain their quality of life. In addition, this metered‐dose cannabis inhaler enables the individualization of medical cannabis regimens that can be evaluated pharmacokinetically and pharmacodynamically using accepted pharmaceutical models.”

https://onlinelibrary.wiley.com/doi/10.1002/ejp.1605

Study Finds Microdosing THC Reduces Pain Levels”  https://www.painnewsnetwork.org/stories/2020/7/1/study-finds-microdosing-thc-reduces-pain-levels

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Medical Cannabis for the Management of Pain and Quality of Life in Chronic Pain Patients: A Prospective Observational Study

Pain Medicine (Journal) by Oxford University Press

“Objective: To evaluate the short-term and long-term effects of plant-based medical cannabis in a chronic pain population over the course of one year.

Results: Medical cannabis treatment was associated with improvements in pain severity and interference (P < 0.001) observed at one month and maintained over the 12-month observation period. Significant improvements were also observed in the SF-12 physical and mental health domains (P < 0.002) starting at three months. Significant decreases in headaches, fatigue, anxiety, and nausea were observed after initiation of treatment (P ≤ 0.002). In patients who reported opioid medication use at baseline, there were significant reductions in oral morphine equivalent doses (P < 0.0001), while correlates of pain were significantly improved by the end of the study observation period.

Conclusions: Taken together, the findings of this study add to the cumulative evidence in support of plant-based medical cannabis as a safe and effective treatment option and potential opioid medication substitute or augmentation therapy for the management of symptoms and quality of life in chronic pain patients.”

https://pubmed.ncbi.nlm.nih.gov/32556203/

https://academic.oup.com/painmedicine/article-abstract/doi/10.1093/pm/pnaa163/5859722?redirectedFrom=fulltext

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