CBD oil is increasingly recognized for having powerful analgesic properties, without the side effects seen in most opioids or non-steroidal anti-inflammatory drugs (NSAIDs).
Its mode of action differs from other commonly used molecules, which makes CBD useful in cases of intractable pain.
1. Specificities and mechanisms of chronic pain (71)
According to the IASP (International Association for the Study of Pain) definition, pain is “ an unpleasant sensory and emotional experience associated with actual or potential tissue damage .” Pain is subjective: it is primarily based on the patient's feelings, which makes it difficult to quantify and qualify.
There are 2 types of pain: nociceptive pain (burning or inflammation for example), of mechanical or inflammatory origin and neuropathic pain (associated with damage to the CNS and PNS).
If we describe acute pain (a burn for example), the burn will stimulate the nerve endings (nociceptors) in the skin. The information then propagates along the nociceptor nerves, and will then be transmitted to the spinal cord and then to the brain. This is when the signal is identified as pain. At the level of the spinal cord, there is a reflex arc (in order to remove the hand from the heat source for example) as well as the first pain modulation systems involving the neurotransmitter GABA or endorphins .
Acute pain is intense and often brief. Pain is chronic when it recurs for more than 3 months.
Neuropathic pain results from spontaneous hyperactivity of the pain pathways following a dysfunction of the sensory pathways of the central or peripheral nervous system. There are several etiologies: ductal syndrome, diabetes, shingles, HIV or tumor for example. (142)
1. Action of CBD on chronic pain
1.1 Analgesic action of CBD
CBD has been shown to be effective in treating chronic pain as well as acute pain. Several studies demonstrate that the endocannabinoid system is involved centrally and peripherally in the processing of pain signals. Researchers proved that endocannabinoids inhibit , through a retrograde mechanism via CB1 receptors , the release of neurotransmitters controlling nociceptive inputs , and that levels of these neurotransmitters were elevated in these regions, known to be involved in transmission or modulation of pain: sensory endings, skin, dorsal root ganglia. (143)
CBD does not directly stimulate the CB1 receptors involved in pain perception (unlike THC) but it has powerful anti-inflammatory activity . A review published in 2008 evaluated the effectiveness of CBD in relieving chronic pain. They included in their research all studies published between 1980 and 2007 and concluded that CBD was effective in overall pain management, without exhibiting any unwanted side effects . (144)
CBD is an agonist of the TRPV1 receptors involved in pain, and will quickly lead to their desensitization. Capsaicin, a renowned treatment for neuropathic pain, exerts its activity by the same mechanism of action. (145,146)
1.2 Anti-inflammatory action of CBD
The anti-inflammatory effect of CBD is recognized. Indeed, it acts on several levels:
- It activates vanilloid receptors ( TRPV1 ) responsible for the regulation of several inflammatory agents such as TNFalpha , IFNgamma , IL6 , IL4 and IL12 . (100)
- It inhibits the enzymatic activity of COX1 and COX2 , responsible for the production of prostaglandins from arachidonic acid. However, prostaglandin is a mediator of inflammation. (101)
- It activates the PPAR γ receptor , responsible for the regulation of pro-inflammatory proteins. (102)
- It acts as an antagonist of the GPR55 receptor and therefore reduces the production of IL12 , pro-inflammatory. (53)
1.3 CBD reduces opioid intake and withdrawal syndrome
Several studies have shown that CBD administration greatly decreased the dose of opioids prescribed to treat pain, which may be of interest when considering the number of patients complaining of adverse effects from opioids. According to a study published in 2016, the consumption of hemp for medical purposes (i.e. not specifically CBD) is associated with a 64% reduction in opioid consumption , and an improvement in quality of life (45%). ). (147)
Additionally, CBD may ease opioid withdrawal symptoms . (148–150)
Quotes:
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102. De Filippis D, Esposito G, Cirillo C, Cipriano M, De Winter BY, Scuderi C, et al. Cannabidiol Reduces Intestinal Inflammation through the Control of Neuroimmune Axis. PLoS ONE [Internet]. 6 Dec 2011 [cited 30 Oct 2020];6(12). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3232190/
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