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Cannabis -vs- Trigeminal Neuralgia

https://www.ncbi.nlm.nih.gov/pubmed/15578967:  Trigeminal neuralgia is a disorder of paroxysmal and severely disabling facial pain and continues to be a real therapeutic challenge to the clinicians. While the exact cause and pathology of this disorder is uncertain, it is thought that trigeminal neuralgia caused by irritation of the trigeminal nerve. This irritation results from damage due to the change in the blood vessels, the presence of a tumor or other lesions that cause the compression of the trigeminal root. The pain of trigeminal neuralgia is characterized by unilateral pain attacks that start abruptly and last for varying periods of time from minutes to hours. The quality of pain is usually sharp, stabbing, lancinating, and burning. The attacks are initiated by mild stimuli such as light touch of the skin, eating, chewing, washing the face, brushing the teeth, and exposure to wind. Although antiepileptic drug therapy may be beneficial in the treatment of trigeminal neuralgia, up to one-half of the patients become refractory or intolerant to these medications. At present there are few other effective drugs. In cases of lacking effect after pharmacotherapy, surgical options may be considered. Currently there is growing amount of evidence to suggest that the psychoactive ingredient in cannabis and individual cannabinoids may be effective in alleviating neuropathic pain and hyperalgesia. Evidence suggests that cannabinoids may prove useful in pain modulation by inhibiting neuronal transmission in pain pathways. Considering the pronounced antinociceptive effects produced by cannabinoids, they may be a promising therapeutic approach for the clinical management of trigeminal neuralgia.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2503660:  Chronic pain represents an emerging public health issue of massive proportions, particularly in view of aging populations in industrialized nations. Associated facts and figures are daunting: In Europe, chronic musculoskeletal pain of a disabling nature affects over one in four elderly people (Frondini et al 2007), while figures from Australia note that older half of older people suffer persistent pain, and up to 80% in nursing home populations (Gibson 2007). Responses to an ABC News poll in the USA indicated that 19% of adults (38 million) have chronic pain, and 6% (or 12 million) have utilized cannabis in attempts to treat it (ABC News et al 2005).

Particular difficulties face the clinician managing intractable patients afflicted with cancer-associated pain, neuropathic pain, and central pain states (eg, pain associated with multiple sclerosis) that are often inadequately treated with available opiates, antidepressants and anticonvulsant drugs. Physicians are seeking new approaches to treatment of these conditions but many remain concerned about increasing governmental scrutiny of their prescribing practices (Fishman 2006), prescription drug abuse or diversion. The entry of cannabinoid medicines to the pharmacopoeia offers a novel approach to the issue of chronic pain management, offering new hope to many, but also stoking the flames of controversy among politicians and the public alike.

This article will attempt to present information concerning cannabinoid mechanisms of analgesia, review randomized clinical trials (RCTs) of available and emerging cannabinoid agents, and address the many thorny issues that have arisen with clinical usage of herbal cannabis itself (“medical marijuana”). An effort will be made to place the issues in context and suggest rational approaches that may mitigate concerns and indicate how standardized pharmaceutical cannabinoids may offer a welcome addition to the pharmacotherapeutic armamentarium in chronic pain treatment.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2755639:  Neuropathic pain is a debilitating form of chronic pain resulting from nerve injury, disease states, or toxic insults. Neuropathic pain is often refractory to conventional pharmacotherapies, necessitating validation of novel analgesics. Cannabinoids, drugs that share the same target as Δ9-tetrahydrocannabinol (Δ9-THC), the psychoactive ingredient in cannabis, have the potential to address this unmet need. Here, we review studies evaluating cannabinoids for neuropathic pain management in the clinical and preclinical literature. Neuropathic pain associated with nerve injury, diabetes, chemotherapeutic treatment, human immunodeficiency virus, multiple sclerosis, and herpes zoster infection is considered. In animals, cannabinoids attenuate neuropathic nociception produced by traumatic nerve injury, disease, and toxic insults. Effects of mixed cannabinoid CB1/CB2 agonists, CB2 selective agonists, and modulators of the endocannabinoid system (i.e., inhibitors of transport or degradation) are compared. Effects of genetic disruption of cannabinoid receptors or enzymes controlling endocannabinoid degradation on neuropathic nociception are described. Specific forms of allodynia and hyperalgesia modulated by cannabinoids are also considered. In humans, effects of smoked marijuana, synthetic Δ9-THC analogs (e.g., Marinol, Cesamet) and medicinal cannabis preparations containing both Δ9-THC and cannabidiol (e.g., Sativex, Cannador) in neuropathic pain states are reviewed. Clinical studies largely affirm that neuropathic pain patients derive benefits from cannabinoid treatment. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3202504:  Cannabis has been used for millennia as a pain-relieving substance. Evidence suggests that cannabinoids may prove useful in pain modulation by inhibiting neuronal transmission in pain pathways. Considering the pronounced antinociceptive effects produced by cannabinoids, they were proposed to be a promising therapeutic approach for the clinical management of trigeminal neuralgia.78 THC, CBD, and CBD-dimethyl heptyl (DMH) were found to block the release of serotonin from platelets induced by plasma obtained from the patients during migraine attack.79 However, in other reports cannabinoids are much less successful in pain-relieving. In a clinical trial THC did not have any significant effect on ongoing and paroxysmal pain, allodynia, quality of life, anxiety/depression scores and functional impact of pain. These results do not support an overall benefit of THC in pain and quality of life in patients with refractory neuropathic pain.80 Similarly, in an additional clinical trial, no evidence was found81 of analgesic effect of orally administered THC in postoperative pain in humans. Other studies show much better results of pain relief. When THC was given to a patient with familial Mediterranean fever, with chronic relapsing pain and gastrointestinal inflammation, a highly significant reduction in pain was noted.82 Mild improvement was noted with cannabis-based medicines for treatment of chronic pain associated with brachial plexus root avulsion.83 In neuropathic pain patients, median spontaneous pain intensity was significantly lower on THC treatment than on placebo treatment, and median pain relief score (numerical rating scale) was higher.84 It was also effective in treating central pain.85 The administration of single oral doses of THC to patients with cancer pain demonstrated a mild analgesic effect.86,87 Patients who suffer from pain also tend to self-medicate with marijuana. In an anonymous cross-sectional survey, 72 (35 %) of chronic noncancer pain patients reported having used cannabis for relieving pain.88 Cannabis-treated AIDS patients reported improved appetite, muscle pain, nausea, anxiety, nerve pain, depression, and paresthesia.89 Not only THC, but also other cannabinoids can potentially affect different types of pain. Nabilone is a synthetic cannabinoid approved for treatment of severe nausea and vomiting associated with cancer chemotherapy.90In Canada, the United States, and the United Kingdom, nabilone is marketed as Cesamet. A significant decrease in disabling spasticity-related pain of patients with chronic upper motor neuron syndrome (UMNS) was found with nabilone.91 Another cannabinoid, ajulemic acid (AJA), was effective in reducing chronic neuropathic pain,92 although cannabinoid side effects (tiredness, dry mouth, limited power of concentration, dizziness, sweating) were noted. Cannabimimetic effects with ajulemic acid in rodents have also been recorded.