Pain and cannabinoids: Learn how CBD can help
Author: MVZ Kevin Antonio Cárdenas Noriega
Pain is something we've all felt, but did you know there are several types of pain? It doesn't just happen if we get hurt, and it's not always easy to relieve. The cannabinoids in cannabis or hemp help regulate the nervous system and can relieve pain - read on to learn more!
Cannabis basics to treat pain
We have all felt pain, but it is difficult to define it. There are several types of pain and they can be classified according to their cause or origin:
Nociceptive pain is the pain we feel when our tissues or organs are injured, and immune cells react to repair the damage, releasing compounds that cause inflammation and pain. This type of pain is what helps us to protect ourselves, for example, if we get close to something very hot and start to burn, the pain of the burn makes us move away from what caused the pain.
Neuropathic pain is damage directly on the nerves, even if our body is physically well, the injured nerves tell us that it hurts. This commonly happens with diabetes and is the cause of "phantom pain" in people who have undergone amputations.
Centralized pain occurs when there is no tissue or nerve damage, it is due to a malfunction of the central nervous system, as if it were a short circuit that is interpreted as pain.
One function of endocannabinoids (produced by the body's cells) is to modulate communication between neurons, decreasing sensitivity and inflammation. Cannabinoids produced by the cannabis or hemp plant also have these effects. It has also been reported that the endocannabinoid system or SEC can interact with other systems related to pain, for example, activating the same receptors where opioid drugs act.
A thorough study conducted in 2007 by Wallace et al. found that administration of medium doses of THC (4 %) was associated with a decrease in pain.
A clinical case report in 2013 presented a facial cancer patient with pain that could not be controlled with usual medications, including opioids.
When this patient began treatment with nabilone (a synthetic cannabinoid), he described an incredible improvement and decrease in his pain. After a month on nabilone, the patient decreased the frequency and doses of other medications for his pain.
Another study conducted in 2018 employed CBD to try to decrease pain in dogs diagnosed with osteoarthritis and severe pain. The researchers administered CBD at different doses or a placebo every 12 hours for 4 weeks, and measured pain with pain and activity scores(brief canine pain inventory and Hudson activity scores). The authors reported that CBD treatment resulted in a significant decrease in pain compared to the placebo-treated group.
The cannabinoids found in cannabis or hemp may be an alternative to treat pain, although more research is still needed to help us understand how they work in the cannabinoid system to combat pain.
CBD has advantages over other cannabinoids, such as THC, because it does not produce psychotropic effects, but can provide a variety of benefits.
From this point on, the article requires medical knowledge for its reading and comprehension, so it is addressed to health professionals.
Pain
Pain is a complex physiological and psychological process. Pain has long been characterized as a subjective experience comprising physiological, sensory, motivational, affective and cognitive evaluation components. The three main pain systems are nociceptive, neuropathic, and central or centralized.
Nociceptive pain is caused by tissue damage with the consequent secretion of signaling messengers by immune cells, including histamine, serotonin, bradykinin, prostaglandin, tumor necrosis factor alpha (TNF-α) and interleukins (IL-6 and 17), among others. Pain signals travel through peripheral neuronal fibers to the dorsal ganglion roots and subsequently to the spinothalamic tract, thalamus and finally to the cortical area. This type of pain is of importance because it has been considered to be the only one with defensive and warning properties, allowing the physiology of the organism to identify potential tissue damage.
Neuropathic, caused by damage to peripheral sensory nerves. For example, foot pain caused by neuropathic diabetes is not directly located in the foot tissue, but in peripheral nerves as a result of nerve damage and due to this damage the nerves send aberrant signals to higher neural centers.
Central or centralized, is pain caused by amplification of peripheral signals due to a persistent malfunction of the central nervous system (CNS). In the latter system, there is no peripheral tissue damage and pain is present despite no clear peripheral cause (Hill et al., 2017).
Damaged neuronal and non-neuronal cells produce endocannabinoids and endocannabinoid-like mediators. These modulate neural conduction of signals, such as pain signals, mitigating sensitivity and inflammation through activation of CB receptors (Hill et al., 2017). However, numerous non-CB1 or CB2 receptors have been associated with pain sensation. For example, transient receptor potentials (TRPs) (Muller et al., 2019), glycine receptors (GlyR) (Lynch et al., 2017), some voltage-gated ion channels (Moldovan et al., 2013; Tibbs et al., 2016) and other G protein-coupled receptors such as GPR55 (Di Marzo, 2018), among others. Indirect interactions of the endocannabinoid system with other pain-related systems such as the opioid system have also been reported (Russo and Hohmann, 2013).
Some types of pain, such as migraine, fibromyalgia and idiopathic irritable bowel syndrome pain, could be targets for therapy with cannabinoids from cannabis or hemp (Russo and Hohmann, 2013).
Clinical studies for the treatment of pain with cannabinoids
In a thorough randomized placebo-controlled study conducted in 2007, 15 healthy volunteers were experimented with pain and local hyperalgesia with an intradermal injection of capsaicin as a pain model on both forearms in order to evaluate the effects of cannabis inhalation at different doses in acute pain states.
The authors found an association with decreased pain and the administration of medium doses of THC (4 % THC). They also reported that individuals who were administered higher doses of THC (8%) experienced a delayed increase in pain, although the authors associated this with a compound contained in the treatment whose presence they did not determine (Wallace et al., 2007).
A clinical case reported in BMJ Case Reports in 2013 was that of a 56-year-old man who manifested chronic neuropathic pain following excision of a facial carcinoma located on the right side of the lower lip, which subsequently reached the right submandibular gland; the patient had difficulty controlling the pain despite medication. The pain worsened when exposed to hot or cold temperatures, which led to severe disability and social isolation to the point where the individual committed a suicide attempt and was even placed on a waiting list for insertion of a spinal cord stimulator to control the pain.
The pain was overwhelming the effect of the medications he was receiving which consisted of acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), ketamine, diazepam, pregabalin, mirtazapine, citalopram, along with a subsequent rotation to opioid analgesics such as morphine and oxycodone. The patient reported that only oxycodone and ketamine produced a benefit of about 2 hours, but that he felt he was developing tolerance. In 2012 he began treatment with nabilone (synthetic cannabinoid) at a dose of 1 mg twice daily, surprisingly the patient described an incredible improvement. He noted only an itching sensation in the area, but said that for the first time in 4 years he could touch the right side of his face.
Treatment with nabilone was shown to effectively improve her quality of life, allowing her to lead a more or less normal life. After one month on nabilone treatment, she has been able to decrease the frequency and doses of other medications and it is hoped that she will eventually be able to terminate their use (Reynolds and Osborn, 2013).
On the other hand, in a 2018 study in dogs published in Frontiers in Veterinary Science, a CBD-rich oil was used for pain management in 22 dogs that were diagnosed with osteoarthritis and presented with severe pain.
Individuals were administered CBD at doses of 2mg/kg and 8 mg/kg every 12 hours or placebo in vegetable oil equivalent every 12 hours for 4 weeks with 2 weeks of acclimatization.
Pain was measured using thebrief canine pain inventory surveys and Hudsonactivity scores. These surveys assess signs of pain and limitation of normal activities in dogs as a result of pain. The surveys were interpreted by veterinarians; the results and numerical data obtained were used for statistical analysis.
At the conclusion of the study, 16 individuals completed treatment and were included in that analysis. The authors reported a statistically significant decrease in pain during CBD treatment, as opposed to acclimatization time without treatment, and compared to the placebo-treated group (Gamble et al., 2018).
Conclusions
Pain is a major problem worldwide, regardless of its etiology and the species it affects. Improving the quality of life of our patients, both animal and human, is a complex and comprehensive task. Knowing the mechanisms of pain, as well as the interactions between systems such as the enlarged endocannabinoid system or other systems, is of importance to justify and guide more effective therapies to combat it. Cannabinoids (whether from cannabis or hemp, as well as synthetics) could be a powerful tool to achieve this goal. However, in order to recommend them, it is imperative to know their specific mechanisms of action, although at present they are not fully elucidated due to their complexity.
Cannabidiol, for example, has certain advantages over other cannabinoids in some pain conditions, mainly due to its lack of behavioral altering effects. THC also has several medical applications, but being psychotropic and identified as a compound with toxic potential in veterinary patients, its use in veterinary medicine is generally restricted. Synthetic cannabinoids also have advantages, but are not yet as widely used as natural cannabinoids.
Physician Network
Did you know that there is already a safe and legal medicine based on medical cannabis in Mexico? It is available with a prescription from ICAN-affiliated trained physicians, learn more in our Physicians Network.
Did you go to the doctor and he prescribed you some cannabis-based medicine? At Botican we have products that meet health and regulatory standards. For more information, visit our website.
References
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