Today’s article focuses on a novel treatment for the treatment and management of chronic neuropathic pain. Estimates of the population prevalence of chronic pain with neuropathic components range between 6% and 10%. Current pharmacological treatment options (medication) for neuropathic pain afford substantial benefit for only a few people, often with adverse effects that outweigh the benefits.
There is now a dire need to explore other alternative treatment options, with different mechanisms of action for treatment of conditions with chronic neuropathic pain. Cannabis has been used for millennia to reduce pain. Herbal cannabis is currently strongly promoted by some patients and their advocates to treat any type of chronic pain.
Cannabis is one of the most commonly used substances worldwide. The cannabis plant contains over 400 chemical constituents, more than 100 of which are cannabinoids—chemicals unique to the cannabis plant. In the past 20 years, many countries have enacted new cannabis policies, including decriminalization of cannabis possession as well as legalization of medical and recreational cannabis. In this context of heightened discussion about the risks and benefits of cannabis, various countries have considered cannabis as a possible treatment for several debilitating medical conditions, such as neuropathic pain.
What is Neuropathic Pain?
Neuropathic pain is defined by the International Association for the Study of Pain (IASP) as “pain caused by a lesion or disease of the somatosensory nervous system’”
The definition was reviewed and updated because the term dysfunction in the old definition was thought to be over-inclusive and did not reflect the pathophysiology. Additionally, neuropathic pain is not one disease entity, rather several diseases or lesions with a cluster of symptoms and signs, where understanding of pathophysiology is evolving.
Neuropathic Pain Treatment and Cannabis
Several products based on the cannabis plant have been suggested as treatment for pain, including neuropathic pain. These products include inhaled herbal cannabis, and various sprays or tablets containing active cannabis ingredients obtained from the plant or made synthetically.
Some people with neuropathic pain claim that cannabis‐based products are effective for them, and that is often highlighted in the media. For instance, a clinical study conducted in 2017 studying the efficacy of cannabis products to treat conditions with chronic neuropathic pain in adults. Results from the study indicated that:
- ‘All cannabis‐based medicines pooled together were better than placebo for the outcomes substantial and moderate pain relief and global improvement.’
- ‘All cannabis‐based medicines pooled together were better than placebo in reducing pain intensity, sleep problems and psychological distress.’
Additionally, many cultures throughout history have used cannabis to treat a variety of painful ailments. Neuropathic pain is a complicated condition that is challenging to treat with our current medications. Recent scientific discovery has elucidated the intricate role of the endocannabinoid system in the pathophysiology of neuropathic pain. As societal perceptions change, and legislation on medical cannabis relaxes, there is growing interest in the use of medical cannabis for neuropathic pain.
Conditions with Moderate-to-High Evidence for Efficaciousness
We examined current basic scientific research and data from recent randomized controlled trials (RCTs) evaluating medical cannabis for the treatment of neuropathic pain. These studies involved patients with diverse etiologies of neuropathic pain and included medical cannabis with different THC concentrations and routes of administration. Multiple RCTs demonstrated efficacy of medical cannabis for treating neuropathic pain, with number needed to treat (NNT) values similar to current pharmacotherapies.
Chronic Pain and Neuropathic Pain
There is a small number of indications for which there is substantial evidence supporting the efficacy of medical cannabis pharmacotherapy. For instance, there have been several studies showing that cannabis can be an effective pharmacotherapy for both chronic pain and neuropathic pain. The effectiveness of cannabis in treating pain was initially demonstrated in preclinical studies. The endocannabinoid system was hypothesized to play an active role in controlling pain, and animal pain models were employed to support this hypothesis.
- THC was shown to produce analgesic and anti-hyperalgesia (sensitivity to pain) effects in mice. These analgesic effects have been supported anecdotally in patients with chronic pain, and many clinical studies have aimed to investigate these effects in human models.
- Whiting and colleges conducted a systematic review and meta‑analysis of randomized clinical trials of cannabis and cannabinoids. This review analyzed twenty-eight studies assessing chronic pain in a total of 2,454 participants. Overall, there was a higher reduction in pain measures with cannabinoids when compared with placebo. A recent report released by the National Academy of Science, Engineering, and Medicine in the United States stipulated that there was “conclusive or substantial evidence” that cannabis or cannabinoids are effective treatments for chronic pain. Finally, another review determined that there was “high quality evidence,” as demonstrated by multiple positive randomized placebo-controlled trials, to support the administration of cannabis or cannabinoid pharmacotherapy for treating chronic pain and neuropathic pain.
Spasticity Associated with Multiple-Sclerosis (MS)
As of October 2017, there have been at least 14 randomized clinical trials aimed at showing the efficacy of cannabis treatment for spasticity associated with multiple sclerosis. Many of these studies showed that cannabis or cannabinoids was helpful in relieving spasticity in patients diagnosed with MS. The American Academy of Neurology found these results promising, leading to the release of evidence‑based guidelines for physicians recommending a cannabis oral extract containing both THC and cannabidiol (CBD) for the treatment of spasticity and pain associated with multiple sclerosis. The symptoms most often found to be alleviated with cannabis were:
- muscle stiffness
- spasticity and,
- sleep disturbances
**Infant(s) – Adolescent(s)
Much of the evidence in favor of cannabinoids for epilepsy in children has been based on self‑reports and anecdotal evidence. Studies on the perceived efficacy of the use of CBD‑enriched cannabis in children with epilepsy have shown a significant reduction of both the frequency and severity of seizures in a variety of seizure disorders.
- In a study of 19 children, aged 2 to 16 years, with diagnoses of Dravet syndrome, Lennox–Gastaut syndrome, and idiopathic epilepsy, complete seizure freedom and an improvement of seizures was reported in 11% and 84% of patients, respectively.
- In a survey‑based study of 117 parents of children with infantile spasms and Lennox–Gastaut syndrome, 14% of patients were completely seizure‑free, and 85% of parents reported a reduction in seizure frequency after cannabis pharmacotherapy.
- Other beneficial effects of CBD in children with epilepsy syndromes include improved sleep, alertness, and mood, as well as an increased appetite.
In the first reported double‑blind placebo‑controlled trial of a cannabinoid for Dravet syndrome, CBD significantly reduced the median frequency of convulsive seizures per month and significantly improved the patient’s overall condition measured on the Caregiver Global Impression of Change scale, when compared with placebo.
Studies on the effectiveness of cannabinoids in adults with epilepsy have provided mixed results. It was shown that men who used cannabis up to 90 days before hospitalization were at a significantly lower risk for a new seizure than men who did not use cannabis. In another study of adults with epilepsy, most patients associated cannabis use with a reduction in the severity and frequency of seizures. In summary, research pertaining to the efficacy of cannabis in treating seizure disorders in adults is still in its infancy and requires further scientific exploration.
As research into cannabis and its efficacy as a medication continues, medical professionals should stay informed on these findings. Cannabis and cannabinoids are promising therapeutics in several areas of medicine. Professionals should rely on facts and research, not public opinion, to inform medical decisions. Cannabis is often used for recreational purposes, but this should not affect how physicians view data collected on its efficacy in treating certain medical conditions.
The evidence appears to support the safety and efficacy of short-term, low-dose cannabis vaporization and oral mucosal delivery for the treatment of neuropathic pain. The results suggest medical cannabis may be as tolerable and effective as current neuropathic agents; however, more studies are needed to determine the long-term effects of medical cannabis use. Furthermore, continued research to optimize dosing, cannabinoid ratios, and alternate routes of administration may help to refine the therapeutic role of medical cannabis for neuropathic pain.