Using Cannabis to Treat Cancer-Related Pain

ObjectiveTo describe which cannabinoids and terpenes are effective for treating pain.Data SourcesPeer-reviewed articles, book chapters.ConclusionCannabis and cannabinoid medicines, as modulators of the endocannabinoid system, offer novel therapeutic options for the treatment of cancer-related pain, not only for patients who do not respond to conventional therapies, but also for patients who prefer to try cannabis as a first treatment option.Implications for Nursing PracticeUnderstanding the endocannabinoid system, cannabinoids, terpenes, routes of administration, potential drug interactions, clinical implications, and potential side effects ensures nurses can better assist patients who use cannabis for the treatment of cancer pain.     

An Integrated Review of Cannabis and Cannabinoids in Adult Oncologic Pain Management

ObjectiveThe objective of this paper is to review the available literature regarding the use of cannabis and cannabinoids in adult oncologic pain management.Design and Data SourcesA integrative review was conducted on March 1, 2018 using PubMed, MEDLINE, CINAHL, Embase, and Scopus. A snowball method was used to extract studies included in systematic reviews that were not included in the primary literature search.Review MethodArticles reviewed address the use of cannabinoids or cannabis for pain management in oncology patients, either as stand- alone or adjuvant therapy.ResultsThe final number of articles included is nine articles. Of the nine studies reviewed, eight reviewed the effect of the cannabinoid THC on cancer pain, and one study reviewed the use of medicinally available whole plant cannabis. The following study types were included: multiple multi-center, randomized, placebo- controlled trials and two prospective observational survey studies.Results and ConclusionsOf the eight studies that reviewed the effect of the cannabinoid THC, five found THC to be more effective than placebo, one found THC to be more effective than placebo in American patients but ineffective in patients from other countries, and two found THC to be no more effective than placebo. The study that reviewed the effect of the whole plant cannabis found that there was a significant decrease in pain among those patients smoking cannabis.Nursing Practice ImplicationsThe lack of evidence in this field of research suggests a need to change policy surrounding cannabis research.     

Cannabinoids: Medical implications

Herbal cannabis has been used for thousands of years for medical purposes. With elucidation of the chemical structures of tetrahydrocannabinol (THC) and cannabidiol (CBD) and with discovery of the human endocannabinoid system, the medical usefulness of cannabinoids has been more intensively explored. While more randomized clinical trials are needed for some medical conditions, other medical disorders, like chronic cancer and neuropathic pain and certain symptoms of multiple sclerosis, have substantial evidence supporting cannabinoid efficacy. While herbal cannabis has not met rigorous FDA standards for medical approval, specific well-characterized cannabinoids have met those standards. Where medical cannabis is legal, patients typically see a physician who “certifies” that a benefit may result. Physicians must consider important patient selection criteria such as failure of standard medical treatment for a debilitating medical disorder. Medical cannabis patients must be informed about potential adverse effects, such as acute impairment of memory, coordination and judgment, and possible chronic effects, such as cannabis use disorder, cognitive impairment, and chronic bronchitis. In addition, social dysfunction may result at work/school, and there is increased possibility of motor vehicle accidents. Novel ways to manipulate the endocannbinoid system are being explored to maximize benefits of cannabinoid therapy and lessen possible harmful effects.

• Key messages

• The medical disorders with the current best evidence that supports a benefit for cannabinoid use are the following: multiple sclerosis patient-reported symptoms of spasticity (nabiximols, nabilone, dronabinol, and oral cannabis extract), multiple sclerosis central pain or painful spasms (nabiximols, nabilone, dronabinol, and oral cannabis extract), multiple sclerosis bladder frequency (nabiximols), and chronic cancer pain/neuropathic pain (nabiximols and smoked THC).

• Herbal cannabis has not met rigorous US FDA standards for medical approval, while specific well-characterized cannabinoids have met those standards, and more are being studied. However, herbal cannabis is legal for medical use in certain US states/countries, and patients must usually see a physician who “certifies” that a benefit may result. Participating physicians should be knowledgeable about cannabinoids, closely look at the risk/benefit ratio, and consider certain important criteria in selecting a patient, such as: age, severity, and nature of the medical disorder, prior or current serious psychiatric or substance use disorder, failure of standard medical therapy as well as failure of an approved cannabinoid, serious underlying cardiac/pulmonary disease, agreement to follow-up visits, and acceptance of the detailed explanation of potential adverse risks.

• The limitations of use of medical cannabis include the following potential adverse effects that are discussed with potential patients: acute central nervous system effects such as deficits in memory, judgment, attention, coordination, and perception (such as time and color), anxiety, dysphoria, and psychosis; chronic central nervous system effects such as cannabis use disorder, cognitive and memory deficits, and increased risk of psychosis; pulmonary effects such as chronic bronchitis; social dysfunction, such as work/school; increased risk of accidents, such as motor vehicle accidents; and preliminary data suggest possible risk for acute cardiovascular event, especially with underlying heart disease.

• The normal human endocannabinoid system is important in the understanding of such issues as normal physiology, cannabis use disorder, and the development of medications that may act as agonists or antagonists to CB1 and CB2. By understanding the endocannabinoid system, it may be possible to enhance the beneficial effects of cannabinoid-related medication, while reducing the harmful effects.

     

Therapeutic Use of Synthetic Cannabinoids: Still an OpenIssue?

Cannabis sativa has a long history of use for medical purposes despite marijuana's addictive potential. The discovery of the endogenous cannabinoid system as a neuromodulatory system composed of receptors, endogenous ligands (endocannabinoids), and enzymes responsible for their synthesis and degradation, together with recent advancements in the elucidation of cannabinoid pharmacology, has renewed interest in medicines acting on the endocannabinoid system. Synthetic cannabinoid agonists have been developed and used for treatment of different human pathologic conditions, and promising potent cannabinoid antagonists are currently under clinical evaluation. During the last decade, new generations of synthetic cannabinoids appeared on the global drug market, proposed as marijuana-like compounds and sold as herbal mixture also known as spice drugs or legal highs. Because activation of cannabinoid receptors may induce central and peripheral beneficial effects, the newest synthetic cannabinoids having full agonistic activity and high potency at cannabinoid type 1 and type 2 receptors might have therapeutic potential too. However, case reports of acute and fatal intoxications are accumulating and revealing that this is not the case because adverse effects of the latest generation of synthetic cannabinoids far exceed the desired ones.     

Cannabinoide—Signaltransduktion und Wirkung

The therapeutic use of cannabinoids, the components of cannabis sativa L., was investigated in numerous researches in detail. Animal studies revealed that cannabinoid receptor agonists alter pain-associated behaviour, have immune-suppressive properties, suppress tumor growth, modulate sensitisation processes and influence memory and learning. Those effects are mediated by two membrane-bound cannabinoid receptors and as mechanisms of signal transduction blockade of ion channels, inhibition of adenylate cyclase and retrograde inhibition of neurotransmitter release are currently being discussed.In clinical studies oral administration of cannabinoids indicated beneficial results during the therapy of multiple sclerosis, weight loss, nausea and vomiting due to chemotherapy, and intractable pruritus. However, therapy of chronic pain conditions revealed conflicting results and unequivocal success could not have been delivered due to unwanted side effects. Further multicentre studies are required to estimate cannabinoids as novel therapeutic tools for the treatment of chronic pain.     

Cannabinoids

Controversy is associated with the issue of cannabis and cannabinoids in clinical care in the United States. Recent research has demonstrated the underlying mechanisms of cannabinoid analgesia via endocannabinoids, an endogenous system of retrograde neuromodulatory messengers that work in tandem with endogenous opioids. Additional receptor and non-receptor mechanisms of cannabinoid drugs have pertinent activity, including anti-carcinogenesis and neuroprotection, that may be of key importance in aging and terminal patient populations. The results of clinical trials with synthetic and plant-based cannabinoids suggest that the role of formulation and delivery system is critical in optimizing the risk-benefit profile of cannabinoid products. Synergy between opioids and cannabinoids may produce opioidsparing effects, as well as extend the duration of analgesia and reduce opioid tolerance and dependence. This article reviews the mechanism of action of cannabinoids, examines marketed agents and those in clinical trials, and addresses their role in treatment of chronic pain, cancer, neurodegenerative diseases, and HIV/ AIDS. The ability of cannabinoid medicines to treat pain, associated sleep disorders, appetite loss, muscle spasm and a wide variety of other symptoms suggests that such agents may in the future play an important role in palliative care.     

Endocannabinoid involvement in endometriosis

Endometriosis is a disease common in women that is defined by abnormal extrauteral growths of uterine endometrial tissue and associated with severe pain. Partly because how the abnormal growths become associated with pain is poorly understood, the pain is difficult to alleviate without resorting to hormones or surgery, which often produce intolerable side effects or fail to help. Recent studies in a rat model and women showed that sensory and sympathetic nerve fibers sprout branches to innervate the abnormal growths. This situation, together with knowledge that the endocannabinoid system is involved in uterine function and dysfunction and that exogenous cannabinoids were once used to alleviate endometriosis-associated pain, suggests that the endocannabinoid system is involved in both endometriosis and its associated pain. Herein, using a rat model, we found that CB1 cannabinoid receptors are expressed on both the somata and fibers of both the sensory and sympathetic neurons that innervate endometriosis’s abnormal growths. We further found that CB1 receptor agonists decrease, whereas CB1 receptor antagonists increase, endometriosis-associated hyperalgesia. Together these findings suggest that the endocannabinoid system contributes to mechanisms underlying both the peripheral innervation of the abnormal growths and the pain associated with endometriosis, thereby providing a novel approach for the development of badly-needed new treatments.     

Cannabinoids:their role in pain and palliation

Controversy is associated with the issue of cannabis and cannabinoids in clinical care in the United States. Recent research has demonstrated the underlying mechanisms of cannabinoid analgesia via endocannabinoids, an endogenous system of retrograde neuromodulatory messengers that work in tandem with endogenous opioids. Additional receptor and non-receptor mechanisms of cannabinoid drugs have pertinent activity, including anti-carcinogenesis and neuroprotection, that may be of key importance in aging and terminal patient populations. The results of clinical trials with synthetic and plant-based cannabinoids suggest that the role of formulation and delivery system is critical in optimizing the risk-benefit profile of cannabinoid products. Synergy between opioids and cannabinoids may produce opioid-sparing effects, as well as extend the duration of analgesia and reduce opioid tolerance and dependence. This article reviews the mechanism of action of cannabinoids, examines marketed agents and those in clinical trials, and addresses their role in treatment of chronic pain, cancer, neurodegenerative diseases, and HIV/ AIDS. The ability of cannabinoid medicines to treat pain, associated sleep disorders, appetite loss, muscle spasm and a wide variety of other symptoms suggests that such agents may in the future play an important role in palliative care.     

Rimonabant--a selective CB1 antagonist

OBJECTIVE: To review the pharmacology, pharmacokinetics, clinical efficacy, and safety of rimonabant, a new selective cannabinoid receptor antagonist. DATA SOURCES: Primary literature and review articles were obtained via a MEDLINE search (1966-November 2004) using the key terms obesity, smoking cessation, cannabinoid, rimonabant, SR 141716, and SR 141716a. Additional studies and abstracts were identified from the bibliographies of reviewed literature. STUDY SELECTION AND DATA EXTRACTION: Studies and review articles related to rimonabant and the endocannabinoid system were reviewed. Data pertinent to this article were included. DATA SYNTHESIS: Rimonabant is a selective cannabinoid receptor antagonist. Recent data have demonstrated beneficial effects of rimonabant in obesity, smoking cessation, and metabolic syndrome. Animal studies using rimonabant have shown a positive role for reducing hunger, caloric intake, and body weight and in increasing satiety. In humans, rimonabant appears to be effective for treatment of obesity and smoking cessation. Ongoing studies will examine the effect of rimonabant on obesity, metabolic syndrome, smoking cessation, and alcohol abuse. To date, the incidence of adverse effects with rimonabant has been slightly greater than placebo, with the most common being nausea. CONCLUSIONS: Rimonabant appears to be a promising drug in an entirely new class called selective cannabinoid CB1 receptor antagonists. The drug may be approved for treatment of obesity and smoking cessation in 2005. Additional studies are ongoing that may provide information on other clinical uses for this medication.     

Cannabinoids and multiple sclerosis

There is a growing amount of evidence to suggest that cannabis and individual cannabinoids may be effective in suppressing certain symptoms of multiple sclerosis and spinal cord injury, including spasticity and pain. Anecdotal evidence is to be found in newspaper reports and also in responses to questionnaires. Clinical evidence comes from trials, albeit with rather small numbers of patients. These trials have shown that cannabis, Delta(9)-tetrahydrocannabinol, and nabilone can produce objective and/or subjective relief from spasticity, pain, tremor, and nocturia in patients with multiple sclerosis (8 trials) or spinal cord injury (1 trial). The clinical evidence is supported by results from experiments with animal models of multiple sclerosis. Some of these experiments, performed with mice with chronic relapsing experimental allergic encephalomyelitis (CREAE), have provided strong evidence that cannabinoid-induced reductions in tremor and spasticity are mediated by cannabinoid receptors, both CB(1) and CB(2). Endocannabinoid concentrations are elevated in the brains and spinal cords of CREAE mice with spasticity, and in line with this observation, spasticity exhibited by CREAE mice can be ameliorated by inhibitors of endocannabinoid membrane transport or enzymic hydrolysis. Research is now needed to establish whether increased endocannabinoid production occurs in multiple sclerosis. Future research should also be directed at obtaining more conclusive evidence about the efficacy of cannabis or individual cannabinoids against the signs and symptoms of these disorders, at devising better modes of administration for cannabinoids and at exploring strategies that maximize separation between the sought-after therapeutic effects and the unwanted effects of these drugs.     

Established and potential therapeutic applications of cannabinoids in oncology

Cannabis occurs naturally in the dried flowering or fruiting tops of the Cannabis sativa plant. Cannabis is most often consumed by smoking marihuana. Cannabinoids are the active compounds extracted from cannabis. Recently, there has been renewed interest in cannabinoids for medicinal purposes. The two proven indications for the use of the synthetic cannabinoid (dronabinol) are chemotherapy-induced nausea and vomiting and AIDS-related anorexia. Other possible effects that may prove beneficial in the oncology population include analgesia, antitumor effect, mood elevation, muscle relaxation, and relief of insomnia. Two types of cannabinoid receptors, CB1 and CB2, have been detected. CB1 receptors are expressed mainly in the central and peripheral nervous system. CB2 receptors are found in certain nonneuronal tissues, particularly in the immune cells. Recent discovery of both the cannabinoid receptors and endocannabinoids has opened a new era in research on the pharmaceutical applications of cannabinoids. The use of cannabinoids should be continued in the areas indicated, and further studies are needed to evaluate other potential uses in clinical oncology.     

The cannabinoid system and its pharmacological manipulation--a review, with emphasis upon the uptake and hydrolysis of anandamide

Although cannabis has been used both recreationally and for medicinal purposes since ancient times, it was not until the 1990s that the receptors responsible for many of the actions of Delta(9)-tetrahydrocannabinol, the main psychoactive ingredient of cannabis, were cloned. Since then, our knowledge of the endogenous cannabinoid system, its physiology, pharmacology and therapeutic potential have expanded enormously. In the present review, the cannabinoid system is described, with particular emphasis on the mechanisms of removal and metabolism of the endocannabinoid signalling molecule anandamide. The current literature shows that cells can accumulate anandamide, and that this process can be disrupted pharmacologically, but that the nature of the mechanism(s) involved remains a matter of some debate. The main enzyme for the hydrolysis of anandamide, fatty acid amide hydrolase, is well characterized, and molecules selectively inhibiting this enzyme have potential therapeutic utility in a number of areas, in particular for the treatment of pain conditions.     

Cannabinoid hyperemesis syndrome: potential mechanisms for the benefit of capsaicin and hot water hydrotherapy in treatment

Introduction: Cannabinoid hyperemesis syndrome is a clinical disorder that has become more prevalent with increasing use of cannabis and synthetic cannabinoids, and which is difficult to treat. Standard antiemetics commonly fail to alleviate the severe nausea and vomiting characteristic of the syndrome. Curiously, cannabinoid hyperemesis syndrome patients often report dramatic relief of symptoms with hot showers and baths, and topical capsaicin.

Objectives: In this review, we detail the pharmacokinetics and pharmacodynamics of capsaicin and explore possible mechanisms for its beneficial effect, including activation of transient receptor potential vanilloid 1 and neurohumoral regulation. Putative mechanisms responsible for the benefit of hot water hydrotherapy are also investigated.

Methods: An extensive search of PubMed, OpenGrey, and Google Scholar from inception to April 2017 was performed to identify known and theoretical thermoregulatory mechanisms associated with the endocannabinoid system. The searches resulted in 2417 articles. These articles were screened for relevant mechanisms behind capsaicin and heat activation having potential antiemetic effects. References from the selected articles were also hand-searched. A total of 137 articles were considered relevant and included.

Capsaicin: Topical capsaicin is primarily used for treatment of neuropathic pain, but it has also been used successfully in some 20 cases of cannabinoid hyperemesis syndrome. The pharmacokinetics and pharmacodynamics of capsaicin as a transient receptor potential vanilloid 1 agonist may explain this effect. Topical capsaicin has a longer half-life than oral administration, thus its potential duration of benefit is longer.

Capsaicin and transient receptor potential vanilloid 1: Topical capsaicin binds and activates the transient receptor potential vanilloid 1 receptor, triggering influx of calcium and sodium, as well as release of inflammatory neuropeptides leading to transient burning, stinging, and itching. This elicits a novel type of desensitization analgesia. Transient receptor potential vanilloid 1 receptors also respond to noxious stimuli, such as heat (>43?°C), acids (pH <6), pain, change in osmolarity, and endovanilloids. The action of topical capsaicin may mimic the effect of heat-activation of transient receptor potential vanilloid 1.

Endocannabinoid system and transient receptor potential vanilloid 1: Cannabinoid hyperemesis syndrome may result from a derangement in the endocannabinoid system secondary to chronic exogenous stimulation. The relief of cannabinoid hyperemesis syndrome symptoms from heat and use of transient receptor potential vanilloid 1 agonists suggests a complex interrelation between the endocannabinoid system and transient receptor potential vanilloid 1.

Temperature regulation: Hot water hydrotherapy is a mainstay of self-treatment for cannabinoid hyperemesis syndrome patients. This may be explained by heat-induced transient receptor potential vanilloid 1 activation.

“Sensocrine” antiemetic effects: Transient receptor potential vanilloid 1 activation by heat or capsaicin results in modulation of tachykinins, somatostatin, pituitary adenylate-cyclase activating polypeptide, and calcitonin gene-related peptide as well as histaminergic, cholinergic, and serotonergic transmission. These downstream effects represent further possible explanations for transient receptor potential vanilloid 1-associated antiemesis.

Conclusions: These complex interactions between the endocannabinoid systems and transient receptor potential vanilloid 1, in the setting of cannabinoid receptor desensitization, may yield important clues into the pathophysiology and treatment of cannabinoid hyperemesis syndrome. This knowledge can provide clinicians caring for these patients with additional treatment options that may reduce length of stay, avoid unnecessary imaging and laboratory testing, and decrease the use of potentially harmful medications such as opioids.     

The future of cannabinoids as analgesic agents: a pharmacologic, pharmacokinetic, and pharmacodynamic overview

For thousands of years, physicians and their patients employed cannabis as a therapeutic agent. Despite this extensive historical usage, in the Western world, cannabis fell into disfavor among medical professionals because the technology available in the 1800s and early 1900s did not permit reliable, standardized preparations to be developed. However, since the discovery and cloning of cannabinoid receptors (CB1 and CB2) in the 1990s, scientific interest in the area has burgeoned, and the complexities of this fascinating receptor system, and its endogenous ligands, have been actively explored. Recent studies reveal that cannabinoids have a rich pharmacology and may interact with a number of other receptor systems-as well as with other cannabinoids-to produce potential synergies. Cannabinoids-endocannabinoids, phytocannabinoids, and synthetic cannabinoids-affect numerous bodily functions and have indicated efficacy of varying degrees in a number of serious medical conditions. Nevertheless, despite promising preclinical and early clinical data, particularly in the areas of inflammation and nociception, development challenges abound. Tetrahydrocannabinol (THC) and other CB1 receptor agonists can have an undesirable CNS impact, and, in many cases, dose optimization may not be realizable before onset of excessive side effects. In addition, complex botanically derived cannabinoid products must satisfy the demanding criteria of the U.S. Food and Drug Association's approval process. Recent agency guidance suggests that these obstacles are not insurmountable, although cannabis herbal material ("medical marijuana") may present fatal uncertainties of quality control and dosage standardization. Therefore, formulation, composition, and delivery system issues will affect the extent to which a particular cannabinoid product may have a desirable risk-benefit profile and acceptable abuse liability potential. Cannabinoid receptor agonists and/or molecules that affect the modulation of endocannabinoid synthesis, metabolism, and transport may, in the future, offer extremely valuable tools for the treatment of a number of currently intractable disorders. Further research is warranted to explore the therapeutic potential of this area.     

Study of cannabinoid dependence in animals

Different animal models have been used to clarify the consequences of chronic exposure to cannabinoid agonists and their abuse liability. Following the chronic administration of cannabinoids, tolerance develops to most of their pharmacological effects. The development of cannabinoid tolerance is particularly rapid, and seems to be due to pharmacodynamic events. A cross-tolerance among different exogenous cannabinoid agonists has been reported. Somatic signs of spontaneous withdrawal have not been reported after chronic Delta(9)-tetrahydrocannabinol (THC) treatment, but were observed after chronic treatment with the cannabinoid agonist WIN-55,212-2. The administration of the CB(1) cannabinoid antagonist SR141716A in animals chronically treated with THC and other cannabinoid agonists precipitated somatic manifestations of withdrawal. The potential ability of anandamide to induce physical dependence has not been clarified. Subjective drug effects of cannabinoids have been reported by drug discrimination studies, which show cross discrimination among different natural and synthetic agonists. The rewarding effects of cannabinoids have been revealed by using several paradigms: place conditioning, intracranial self-stimulation, and self-administration. Cannabinoids have been reported to lower intracranial self-stimulation thresholds in rats. However, particular experimental conditions are required to induce conditioned place preference with cannabinoids. Numerous studies have shown that THC is unable to induce a self-administration behaviour in animals. However, WIN-55,212-2 was intravenously self-administered in mice, and monkeys that had a previous history of cocaine self-administration also self-administered THC. The mesolimbic dopaminergic system seems to be the substrate for the rewarding properties of cannabinoids.     

Amygdala activity contributes to the dissociative effect of cannabis on pain perception

Cannabis is reported to be remarkably effective for the relief of otherwise intractable pain. However, the bases for pain relief afforded by this psychotropic agent are debatable. Nonetheless, the frontal-limbic distribution of cannabinoid receptors in the brain suggests that cannabis may target preferentially the affective qualities of pain. This central mechanism of action may be relevant to cannabinoid analgesia in humans, but has yet to be demonstrated. Here, we employed functional magnetic resonance imaging to investigate the effects of delta-9-tetrahydrocannabinol (THC), a naturally occurring cannabinoid, on brain activity related to cutaneous ongoing pain and hyperalgesia that were temporarily induced by capsaicin in healthy volunteers. On average, THC reduced the reported unpleasantness, but not the intensity of ongoing pain and hyperalgesia: the specific analgesic effect on hyperalgesia was substantiated by diminished activity in the anterior mid cingulate cortex. In individuals, the drug-induced reduction in the unpleasantness of hyperalgesia was positively correlated with right amygdala activity. THC also reduced functional connectivity between the amygdala and primary sensorimotor areas during the ongoing-pain state. Critically, the reduction in sensory-limbic functional connectivity was positively correlated with the difference in drug effects on the unpleasantness and the intensity of ongoing pain. Peripheral mechanisms alone cannot account for the dissociative effects of THC on the pain that was observed. Instead, the data reveal that amygdala activity contributes to interindividual response to cannabinoid analgesia, and suggest that dissociative effects of THC in the brain are relevant to pain relief in humans.     

Cannabinoids suppress inflammatory and neuropathic pain by targeting α3 glycine receptors

Certain types of nonpsychoactive cannabinoids can potentiate glycine receptors (GlyRs), an important target for nociceptive regulation at the spinal level. However, little is known about the potential and mechanism of glycinergic cannabinoids for chronic pain treatment. We report that systemic and intrathecal administration of cannabidiol (CBD), a major nonpsychoactive component of marijuana, and its modified derivatives significantly suppress chronic inflammatory and neuropathic pain without causing apparent analgesic tolerance in rodents. The cannabinoids significantly potentiate glycine currents in dorsal horn neurons in rat spinal cord slices. The analgesic potency of 11 structurally similar cannabinoids is positively correlated with cannabinoid potentiation of the α3 GlyRs. In contrast, the cannabinoid analgesia is neither correlated with their binding affinity for CB1 and CB2 receptors nor with their psychoactive side effects. NMR analysis reveals a direct interaction between CBD and S296 in the third transmembrane domain of purified α3 GlyR. The cannabinoid-induced analgesic effect is absent in mice lacking the α3 GlyRs. Our findings suggest that the α3 GlyRs mediate glycinergic cannabinoid-induced suppression of chronic pain. These cannabinoids may represent a novel class of therapeutic agents for the treatment of chronic pain and other diseases involving GlyR dysfunction.     

Recent developments in the pathophysiology of acute pain

Tissue damage induces a state of hyperalgesia. Traditionally, sensory physiology was elucidated by examining responses to ephemeral transient stimuli. However, in order to study acute clinical pain, it is necessary to re-examine nociceptive processing using models which include a significant hyperalgesic component. Primary hyperalgesia results from sensitisation of primary afferent nociceptive neurons by various components of the ‘inflammatory soup’, in a complex interaction between the immune and nervous systems. It is now possible to identify key molecules which participate in this process and exploitation of these may result in the development of novel peripherally acting analgesics:Nerve growth factor: In the developing animal this target-derived growth factor is vital to the survival of the small diameter neurons associated with nociception. However, in the developed animal there is now considerable evidence that this neurotrophin takes on a different role in that it occupies a pivotal position in the development of hyperalgesia. A ligand trap molecule which sequesters nerve growth factor attenuates inflammatory hyperalgesia in several animal models.Bradykinin: Although the potent algogenic effects of bradykinin have been appreciated for some time, the recent discovery of bradykinin receptor sub-types has renewed interest in this molecule. By the use of selective antagonists at the B1 and B2 receptors it has been ascertained that they play disparate roles in nociception and hyperalgesia, thus giving scope for further development.Cannabinoids: Although a component of cannabinoid-induced analgesia is mediated through central (CB1) receptors, the discovery of a second immune cell associated cannabinoid receptor (CB2) has allowed further investigation of the cannabinoids. It appears that putative endogenous CB2 ligands are active during inflammation and attenuate inflammatory hyperalgesia. Exploitation of CB2 receptor agonists may allow the analgesic actions of cannabinoids to be divorced from their CNS side effects.     

Cannabis for Pain and Headaches: Primer

Purpose of Review

Marijuana has been used both medicinally and recreationally since ancient times and interest in its compounds for pain relief has increased in recent years. The identification of our own intrinsic, endocannabinoid system has laid the foundation for further research.

Recent Findings

Synthetic cannabinoids are being developed and synthesized from the marijuana plant such as dronabinol and nabilone. The US Food and Drug Administration approved the use of dronabinol and nabilone for chemotherapy-associated nausea and vomiting and HIV (Human Immunodeficiency Virus) wasting. Nabiximols is a cannabis extract that is approved for the treatment of spasticity and intractable pain in Canada and the UK. Further clinical trials are studying the effect of marijuana extracts for seizure disorders.

Summary

Phytocannabinoids have been identified as key compounds involved in analgesia and anti-inflammatory effects. Other compounds found in cannabis such as flavonoids and terpenes are also being investigated as to their individual or synergistic effects. This article will review relevant literature regarding medical use of marijuana and cannabinoid pharmaceuticals with an emphasis on pain and headaches.

     

The endocannabinoid system and rimonabant: a new drug with a novel mechanism of action involving cannabinoid CB1 receptor antagonism--or inverse agonism--as potential obesity treatment and other therapeutic use

There is considerable evidence that the endocannabinoid (endogenous cannabinoid) system plays a significant role in appetitive drive and associated behaviours. It is therefore reasonable to hypothesize that the attenuation of the activity of this system would have therapeutic benefit in treating disorders that might have a component of excess appetitive drive or over-activity of the endocannabinoid system, such as obesity, ethanol and other drug abuse, and a variety of central nervous system and other disorders. Towards this end, antagonists of cannabinoid receptors have been designed through rational drug discovery efforts. Devoid of the abuse concerns that confound and impede the use of cannabinoid receptor agonists for legitimate medical purposes, investigation of the use of cannabinoid receptor antagonists as possible pharmacotherapeutic agents is currently being actively investigated. The compound furthest along this pathway is rimonabant, a selective CB(1) (cannabinoid receptor subtype 1) antagonist, or inverse agonist, approved in the European Union and under regulatory review in the United States for the treatment of obesity. This article summarizes the basic science of the endocannabinoid system and the therapeutic potential of cannabinoid receptor antagonists, with emphasis on the treatment of obesity.